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GNU GENERAL PUBLIC LICENSE
Version 3, 29 June 2007
Copyright (C) 2007 Free Software Foundation, Inc. <http://fsf.org/>
Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
Preamble
The GNU General Public License is a free, copyleft license for
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The licenses for most software and other practical works are designed
to take away your freedom to share and change the works. By contrast,
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Nothing in this License shall be construed as excluding or limiting
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to collect a royalty for further conveying from those to whom you convey
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License would be to refrain entirely from conveying the Program.
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Notwithstanding any other provision of this License, you have
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14. Revised Versions of this License.
The Free Software Foundation may publish revised and/or new versions of
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option of following the terms and conditions either of that numbered
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If the Program specifies that a proxy can decide which future
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Later license versions may give you additional or different
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THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY
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IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
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If the disclaimer of warranty and limitation of liability provided
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END OF TERMS AND CONDITIONS
How to Apply These Terms to Your New Programs
If you develop a new program, and you want it to be of the greatest
possible use to the public, the best way to achieve this is to make it
free software which everyone can redistribute and change under these terms.
To do so, attach the following notices to the program. It is safest
to attach them to the start of each source file to most effectively
state the exclusion of warranty; and each file should have at least
the "copyright" line and a pointer to where the full notice is found.
<one line to give the program's name and a brief idea of what it does.>
Copyright (C) <year> <name of author>
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
Also add information on how to contact you by electronic and paper mail.
If the program does terminal interaction, make it output a short
notice like this when it starts in an interactive mode:
<program> Copyright (C) <year> <name of author>
This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
This is free software, and you are welcome to redistribute it
under certain conditions; type `show c' for details.
The hypothetical commands `show w' and `show c' should show the appropriate
parts of the General Public License. Of course, your program's commands
might be different; for a GUI interface, you would use an "about box".
You should also get your employer (if you work as a programmer) or school,
if any, to sign a "copyright disclaimer" for the program, if necessary.
For more information on this, and how to apply and follow the GNU GPL, see
<http://www.gnu.org/licenses/>.
The GNU General Public License does not permit incorporating your program
into proprietary programs. If your program is a subroutine library, you
may consider it more useful to permit linking proprietary applications with
the library. If this is what you want to do, use the GNU Lesser General
Public License instead of this License. But first, please read
<http://www.gnu.org/philosophy/why-not-lgpl.html>.

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FFmpeg 64-bit static Windows build from www.gyan.dev
Version: 2023-01-09-git-13d04e30d7-full_build-www.gyan.dev
License: GPL v3
Source Code: https://github.com/FFmpeg/FFmpeg/commit/13d04e30d7
External Assets
frei0r plugins: https://www.gyan.dev/ffmpeg/builds/ffmpeg-frei0r-plugins
lensfun database: https://www.gyan.dev/ffmpeg/builds/ffmpeg-lensfun-db
git-full build configuration:
ARCH x86 (generic)
big-endian no
runtime cpu detection yes
standalone assembly yes
x86 assembler nasm
MMX enabled yes
MMXEXT enabled yes
3DNow! enabled yes
3DNow! extended enabled yes
SSE enabled yes
SSSE3 enabled yes
AESNI enabled yes
AVX enabled yes
AVX2 enabled yes
AVX-512 enabled yes
AVX-512ICL enabled yes
XOP enabled yes
FMA3 enabled yes
FMA4 enabled yes
i686 features enabled yes
CMOV is fast yes
EBX available yes
EBP available yes
debug symbols yes
strip symbols yes
optimize for size no
optimizations yes
static yes
shared no
postprocessing support yes
network support yes
threading support pthreads
safe bitstream reader yes
texi2html enabled no
perl enabled yes
pod2man enabled yes
makeinfo enabled yes
makeinfo supports HTML yes
xmllint enabled yes
External libraries:
avisynth libilbc libtheora
bzlib libjxl libtwolame
chromaprint liblensfun libuavs3d
frei0r libmodplug libvidstab
gmp libmp3lame libvmaf
gnutls libmysofa libvo_amrwbenc
iconv libopencore_amrnb libvorbis
ladspa libopencore_amrwb libvpx
libaom libopenjpeg libwebp
libaribb24 libopenmpt libx264
libass libopus libx265
libbluray libplacebo libxavs2
libbs2b librav1e libxml2
libcaca librist libxvid
libcdio librubberband libzimg
libdav1d libshaderc libzmq
libdavs2 libshine libzvbi
libflite libsnappy lzma
libfontconfig libsoxr mediafoundation
libfreetype libspeex sdl2
libfribidi libsrt zlib
libgme libssh
libgsm libsvtav1
External libraries providing hardware acceleration:
amf dxva2 nvenc
cuda ffnvcodec opencl
cuda_llvm libmfx vulkan
cuvid libvpl
d3d11va nvdec
Libraries:
avcodec avformat swresample
avdevice avutil swscale
avfilter postproc
Programs:
ffmpeg ffplay ffprobe
Enabled decoders:
aac fraps pcm_u24le
aac_fixed frwu pcm_u32be
aac_latm ftr pcm_u32le
aasc g2m pcm_u8
ac3 g723_1 pcm_vidc
ac3_fixed g729 pcx
acelp_kelvin gdv pfm
adpcm_4xm gem pgm
adpcm_adx gif pgmyuv
adpcm_afc gremlin_dpcm pgssub
adpcm_agm gsm pgx
adpcm_aica gsm_ms phm
adpcm_argo h261 photocd
adpcm_ct h263 pictor
adpcm_dtk h263i pixlet
adpcm_ea h263p pjs
adpcm_ea_maxis_xa h264 png
adpcm_ea_r1 h264_cuvid ppm
adpcm_ea_r2 h264_qsv prores
adpcm_ea_r3 hap prosumer
adpcm_ea_xas hca psd
adpcm_g722 hcom ptx
adpcm_g726 hdr qcelp
adpcm_g726le hevc qdm2
adpcm_ima_acorn hevc_cuvid qdmc
adpcm_ima_alp hevc_qsv qdraw
adpcm_ima_amv hnm4_video qoi
adpcm_ima_apc hq_hqa qpeg
adpcm_ima_apm hqx qtrle
adpcm_ima_cunning huffyuv r10k
adpcm_ima_dat4 hymt r210
adpcm_ima_dk3 iac ra_144
adpcm_ima_dk4 idcin ra_288
adpcm_ima_ea_eacs idf ralf
adpcm_ima_ea_sead iff_ilbm rasc
adpcm_ima_iss ilbc rawvideo
adpcm_ima_moflex imc realtext
adpcm_ima_mtf imm4 rl2
adpcm_ima_oki imm5 roq
adpcm_ima_qt indeo2 roq_dpcm
adpcm_ima_rad indeo3 rpza
adpcm_ima_smjpeg indeo4 rscc
adpcm_ima_ssi indeo5 rv10
adpcm_ima_wav interplay_acm rv20
adpcm_ima_ws interplay_dpcm rv30
adpcm_ms interplay_video rv40
adpcm_mtaf ipu s302m
adpcm_psx jacosub sami
adpcm_sbpro_2 jpeg2000 sanm
adpcm_sbpro_3 jpegls sbc
adpcm_sbpro_4 jv scpr
adpcm_swf kgv1 screenpresso
adpcm_thp kmvc sdx2_dpcm
adpcm_thp_le lagarith sga
adpcm_vima libaom_av1 sgi
adpcm_xa libaribb24 sgirle
adpcm_yamaha libdav1d sheervideo
adpcm_zork libdavs2 shorten
agm libgsm simbiosis_imx
aic libgsm_ms sipr
alac libilbc siren
alias_pix libjxl smackaud
als libopencore_amrnb smacker
amrnb libopencore_amrwb smc
amrwb libopenjpeg smvjpeg
amv libopus snow
anm libspeex sol_dpcm
ansi libuavs3d sonic
apac libvorbis sp5x
ape libvpx_vp8 speedhq
apng libvpx_vp9 speex
aptx libzvbi_teletext srgc
aptx_hd loco srt
arbc lscr ssa
argo m101 stl
ass mace3 subrip
asv1 mace6 subviewer
asv2 magicyuv subviewer1
atrac1 mdec sunrast
atrac3 media100 svq1
atrac3al metasound svq3
atrac3p microdvd tak
atrac3pal mimic targa
atrac9 misc4 targa_y216
aura mjpeg tdsc
aura2 mjpeg_cuvid text
av1 mjpeg_qsv theora
av1_cuvid mjpegb thp
av1_qsv mlp tiertexseqvideo
avrn mmvideo tiff
avrp mobiclip tmv
avs motionpixels truehd
avui movtext truemotion1
ayuv mp1 truemotion2
bethsoftvid mp1float truemotion2rt
bfi mp2 truespeech
bink mp2float tscc
binkaudio_dct mp3 tscc2
binkaudio_rdft mp3adu tta
bintext mp3adufloat twinvq
bitpacked mp3float txd
bmp mp3on4 ulti
bmv_audio mp3on4float utvideo
bmv_video mpc7 v210
bonk mpc8 v210x
brender_pix mpeg1_cuvid v308
c93 mpeg1video v408
cavs mpeg2_cuvid v410
ccaption mpeg2_qsv vb
cdgraphics mpeg2video vble
cdtoons mpeg4 vbn
cdxl mpeg4_cuvid vc1
cfhd mpegvideo vc1_cuvid
cinepak mpl2 vc1_qsv
clearvideo msa1 vc1image
cljr mscc vcr1
cllc msmpeg4v1 vmdaudio
comfortnoise msmpeg4v2 vmdvideo
cook msmpeg4v3 vmnc
cpia msnsiren vorbis
cri msp2 vp3
cscd msrle vp4
cyuv mss1 vp5
dca mss2 vp6
dds msvideo1 vp6a
derf_dpcm mszh vp6f
dfa mts2 vp7
dfpwm mv30 vp8
dirac mvc1 vp8_cuvid
dnxhd mvc2 vp8_qsv
dolby_e mvdv vp9
dpx mvha vp9_cuvid
dsd_lsbf mwsc vp9_qsv
dsd_lsbf_planar mxpeg vplayer
dsd_msbf nellymoser vqa
dsd_msbf_planar notchlc vqc
dsicinaudio nuv wavpack
dsicinvideo on2avc wbmp
dss_sp opus wcmv
dst paf_audio webp
dvaudio paf_video webvtt
dvbsub pam wmalossless
dvdsub pbm wmapro
dvvideo pcm_alaw wmav1
dxa pcm_bluray wmav2
dxtory pcm_dvd wmavoice
dxv pcm_f16le wmv1
eac3 pcm_f24le wmv2
eacmv pcm_f32be wmv3
eamad pcm_f32le wmv3image
eatgq pcm_f64be wnv1
eatgv pcm_f64le wrapped_avframe
eatqi pcm_lxf ws_snd1
eightbps pcm_mulaw xan_dpcm
eightsvx_exp pcm_s16be xan_wc3
eightsvx_fib pcm_s16be_planar xan_wc4
escape124 pcm_s16le xbin
escape130 pcm_s16le_planar xbm
evrc pcm_s24be xface
exr pcm_s24daud xl
fastaudio pcm_s24le xma1
ffv1 pcm_s24le_planar xma2
ffvhuff pcm_s32be xpm
ffwavesynth pcm_s32le xsub
fic pcm_s32le_planar xwd
fits pcm_s64be y41p
flac pcm_s64le ylc
flashsv pcm_s8 yop
flashsv2 pcm_s8_planar yuv4
flic pcm_sga zero12v
flv pcm_u16be zerocodec
fmvc pcm_u16le zlib
fourxm pcm_u24be zmbv
Enabled encoders:
a64multi huffyuv pcm_u16le
a64multi5 jpeg2000 pcm_u24be
aac jpegls pcm_u24le
aac_mf libaom_av1 pcm_u32be
ac3 libgsm pcm_u32le
ac3_fixed libgsm_ms pcm_u8
ac3_mf libilbc pcm_vidc
adpcm_adx libjxl pcx
adpcm_argo libmp3lame pfm
adpcm_g722 libopencore_amrnb pgm
adpcm_g726 libopenjpeg pgmyuv
adpcm_g726le libopus phm
adpcm_ima_alp librav1e png
adpcm_ima_amv libshine ppm
adpcm_ima_apm libspeex prores
adpcm_ima_qt libsvtav1 prores_aw
adpcm_ima_ssi libtheora prores_ks
adpcm_ima_wav libtwolame qoi
adpcm_ima_ws libvo_amrwbenc qtrle
adpcm_ms libvorbis r10k
adpcm_swf libvpx_vp8 r210
adpcm_yamaha libvpx_vp9 ra_144
alac libwebp rawvideo
alias_pix libwebp_anim roq
amv libx264 roq_dpcm
apng libx264rgb rpza
aptx libx265 rv10
aptx_hd libxavs2 rv20
ass libxvid s302m
asv1 ljpeg sbc
asv2 magicyuv sgi
av1_nvenc mjpeg smc
av1_qsv mjpeg_qsv snow
avrp mlp sonic
avui movtext sonic_ls
ayuv mp2 speedhq
bitpacked mp2fixed srt
bmp mp3_mf ssa
cfhd mpeg1video subrip
cinepak mpeg2_qsv sunrast
cljr mpeg2video svq1
comfortnoise mpeg4 targa
dca msmpeg4v2 text
dfpwm msmpeg4v3 tiff
dnxhd msvideo1 truehd
dpx nellymoser tta
dvbsub opus ttml
dvdsub pam utvideo
dvvideo pbm v210
eac3 pcm_alaw v308
exr pcm_bluray v408
ffv1 pcm_dvd v410
ffvhuff pcm_f32be vbn
fits pcm_f32le vc2
flac pcm_f64be vorbis
flashsv pcm_f64le vp9_qsv
flashsv2 pcm_mulaw wavpack
flv pcm_s16be wbmp
g723_1 pcm_s16be_planar webvtt
gif pcm_s16le wmav1
h261 pcm_s16le_planar wmav2
h263 pcm_s24be wmv1
h263p pcm_s24daud wmv2
h264_amf pcm_s24le wrapped_avframe
h264_mf pcm_s24le_planar xbm
h264_nvenc pcm_s32be xface
h264_qsv pcm_s32le xsub
hap pcm_s32le_planar xwd
hdr pcm_s64be y41p
hevc_amf pcm_s64le yuv4
hevc_mf pcm_s8 zlib
hevc_nvenc pcm_s8_planar zmbv
hevc_qsv pcm_u16be
Enabled hwaccels:
av1_d3d11va hevc_nvdec vc1_nvdec
av1_d3d11va2 mjpeg_nvdec vp8_nvdec
av1_dxva2 mpeg1_nvdec vp9_d3d11va
av1_nvdec mpeg2_d3d11va vp9_d3d11va2
h264_d3d11va mpeg2_d3d11va2 vp9_dxva2
h264_d3d11va2 mpeg2_dxva2 vp9_nvdec
h264_dxva2 mpeg2_nvdec wmv3_d3d11va
h264_nvdec mpeg4_nvdec wmv3_d3d11va2
hevc_d3d11va vc1_d3d11va wmv3_dxva2
hevc_d3d11va2 vc1_d3d11va2 wmv3_nvdec
hevc_dxva2 vc1_dxva2
Enabled parsers:
aac dvdsub opus
aac_latm flac png
ac3 ftr pnm
adx g723_1 qoi
amr g729 rv30
av1 gif rv40
avs2 gsm sbc
avs3 h261 sipr
bmp h263 tak
cavsvideo h264 vc1
cook hdr vorbis
cri hevc vp3
dca ipu vp8
dirac jpeg2000 vp9
dnxhd misc4 webp
dolby_e mjpeg xbm
dpx mlp xma
dvaudio mpeg4video xwd
dvbsub mpegaudio
dvd_nav mpegvideo
Enabled demuxers:
aa ico pcm_alaw
aac idcin pcm_f32be
aax idf pcm_f32le
ac3 iff pcm_f64be
ace ifv pcm_f64le
acm ilbc pcm_mulaw
act image2 pcm_s16be
adf image2_alias_pix pcm_s16le
adp image2_brender_pix pcm_s24be
ads image2pipe pcm_s24le
adx image_bmp_pipe pcm_s32be
aea image_cri_pipe pcm_s32le
afc image_dds_pipe pcm_s8
aiff image_dpx_pipe pcm_u16be
aix image_exr_pipe pcm_u16le
alp image_gem_pipe pcm_u24be
amr image_gif_pipe pcm_u24le
amrnb image_hdr_pipe pcm_u32be
amrwb image_j2k_pipe pcm_u32le
anm image_jpeg_pipe pcm_u8
apac image_jpegls_pipe pcm_vidc
apc image_jpegxl_pipe pjs
ape image_pam_pipe pmp
apm image_pbm_pipe pp_bnk
apng image_pcx_pipe pva
aptx image_pfm_pipe pvf
aptx_hd image_pgm_pipe qcp
aqtitle image_pgmyuv_pipe r3d
argo_asf image_pgx_pipe rawvideo
argo_brp image_phm_pipe realtext
argo_cvg image_photocd_pipe redspark
asf image_pictor_pipe rl2
asf_o image_png_pipe rm
ass image_ppm_pipe roq
ast image_psd_pipe rpl
au image_qdraw_pipe rsd
av1 image_qoi_pipe rso
avi image_sgi_pipe rtp
avisynth image_sunrast_pipe rtsp
avr image_svg_pipe s337m
avs image_tiff_pipe sami
avs2 image_vbn_pipe sap
avs3 image_webp_pipe sbc
bethsoftvid image_xbm_pipe sbg
bfi image_xpm_pipe scc
bfstm image_xwd_pipe scd
bink imf sdp
binka ingenient sdr2
bintext ipmovie sds
bit ipu sdx
bitpacked ircam segafilm
bmv iss ser
boa iv8 sga
bonk ivf shorten
brstm ivr siff
c93 jacosub simbiosis_imx
caf jv sln
cavsvideo kux smacker
cdg kvag smjpeg
cdxl laf smush
cine libgme sol
codec2 libmodplug sox
codec2raw libopenmpt spdif
concat live_flv srt
dash lmlm4 stl
data loas str
daud lrc subviewer
dcstr luodat subviewer1
derf lvf sup
dfa lxf svag
dfpwm m4v svs
dhav matroska swf
dirac mca tak
dnxhd mcc tedcaptions
dsf mgsts thp
dsicin microdvd threedostr
dss mjpeg tiertexseq
dts mjpeg_2000 tmv
dtshd mlp truehd
dv mlv tta
dvbsub mm tty
dvbtxt mmf txd
dxa mods ty
ea moflex v210
ea_cdata mov v210x
eac3 mp3 vag
epaf mpc vc1
ffmetadata mpc8 vc1t
filmstrip mpegps vividas
fits mpegts vivo
flac mpegtsraw vmd
flic mpegvideo vobsub
flv mpjpeg voc
fourxm mpl2 vpk
frm mpsub vplayer
fsb msf vqf
fwse msnwc_tcp w64
g722 msp wav
g723_1 mtaf wc3
g726 mtv webm_dash_manifest
g726le musx webvtt
g729 mv wsaud
gdv mvi wsd
genh mxf wsvqa
gif mxg wtv
gsm nc wv
gxf nistsphere wve
h261 nsp xa
h263 nsv xbin
h264 nut xmv
hca nuv xvag
hcom obu xwma
hevc ogg yop
hls oma yuv4mpegpipe
hnm paf
Enabled muxers:
a64 h263 pcm_s24be
ac3 h264 pcm_s24le
adts hash pcm_s32be
adx hds pcm_s32le
aiff hevc pcm_s8
alp hls pcm_u16be
amr ico pcm_u16le
amv ilbc pcm_u24be
apm image2 pcm_u24le
apng image2pipe pcm_u32be
aptx ipod pcm_u32le
aptx_hd ircam pcm_u8
argo_asf ismv pcm_vidc
argo_cvg ivf psp
asf jacosub rawvideo
asf_stream kvag rm
ass latm roq
ast lrc rso
au m4v rtp
avi matroska rtp_mpegts
avif matroska_audio rtsp
avm2 md5 sap
avs2 microdvd sbc
avs3 mjpeg scc
bit mkvtimestamp_v2 segafilm
caf mlp segment
cavsvideo mmf smjpeg
chromaprint mov smoothstreaming
codec2 mp2 sox
codec2raw mp3 spdif
crc mp4 spx
dash mpeg1system srt
data mpeg1vcd stream_segment
daud mpeg1video streamhash
dfpwm mpeg2dvd sup
dirac mpeg2svcd swf
dnxhd mpeg2video tee
dts mpeg2vob tg2
dv mpegts tgp
eac3 mpjpeg truehd
f4v mxf tta
ffmetadata mxf_d10 ttml
fifo mxf_opatom uncodedframecrc
fifo_test null vc1
filmstrip nut vc1t
fits obu voc
flac oga w64
flv ogg wav
framecrc ogv webm
framehash oma webm_chunk
framemd5 opus webm_dash_manifest
g722 pcm_alaw webp
g723_1 pcm_f32be webvtt
g726 pcm_f32le wsaud
g726le pcm_f64be wtv
gif pcm_f64le wv
gsm pcm_mulaw yuv4mpegpipe
gxf pcm_s16be
h261 pcm_s16le
Enabled protocols:
async httpproxy rtmpe
bluray https rtmps
cache icecast rtmpt
concat ipfs rtmpte
concatf ipns rtmpts
crypto librist rtp
data libsrt srtp
ffrtmpcrypt libssh subfile
ffrtmphttp libzmq tcp
file md5 tee
ftp mmsh tls
gopher mmst udp
gophers pipe udplite
hls prompeg
http rtmp
Enabled filters:
a3dscope dctdnoiz pad
abench ddagrab pad_opencl
abitscope deband pal100bars
acompressor deblock pal75bars
acontrast decimate palettegen
acopy deconvolve paletteuse
acrossfade dedot pan
acrossover deesser perms
acrusher deflate perspective
acue deflicker phase
addroi deinterlace_qsv photosensitivity
adeclick dejudder pixdesctest
adeclip delogo pixelize
adecorrelate derain pixscope
adelay deshake pp
adenorm deshake_opencl pp7
aderivative despill premultiply
adrawgraph detelecine prewitt
adrc dialoguenhance prewitt_opencl
adynamicequalizer dilation program_opencl
adynamicsmooth dilation_opencl pseudocolor
aecho displace psnr
aemphasis dnn_classify pullup
aeval dnn_detect qp
aevalsrc dnn_processing random
aexciter doubleweave readeia608
afade drawbox readvitc
afftdn drawgraph realtime
afftfilt drawgrid remap
afifo drawtext remap_opencl
afir drmeter removegrain
afirsrc dynaudnorm removelogo
aformat earwax repeatfields
afreqshift ebur128 replaygain
afwtdn edgedetect reverse
agate elbg rgbashift
agraphmonitor entropy rgbtestsrc
ahistogram epx roberts
aiir eq roberts_opencl
aintegral equalizer rotate
ainterleave erosion rubberband
alatency erosion_opencl sab
alimiter estdif scale
allpass exposure scale2ref
allrgb extractplanes scale_cuda
allyuv extrastereo scale_qsv
aloop fade scale_vulkan
alphaextract feedback scdet
alphamerge fftdnoiz scharr
amerge fftfilt scroll
ametadata field segment
amix fieldhint select
amovie fieldmatch selectivecolor
amplify fieldorder sendcmd
amultiply fifo separatefields
anequalizer fillborders setdar
anlmdn find_rect setfield
anlmf firequalizer setparams
anlms flanger setpts
anoisesrc flip_vulkan setrange
anull flite setsar
anullsink floodfill settb
anullsrc format shear
apad fps showcqt
aperms framepack showcwt
aphasemeter framerate showfreqs
aphaser framestep showinfo
aphaseshift freezedetect showpalette
apsyclip freezeframes showspatial
apulsator frei0r showspectrum
arealtime frei0r_src showspectrumpic
aresample fspp showvolume
areverse gblur showwaves
arnndn gblur_vulkan showwavespic
asdr geq shuffleframes
asegment gradfun shufflepixels
aselect gradients shuffleplanes
asendcmd graphmonitor sidechaincompress
asetnsamples grayworld sidechaingate
asetpts greyedge sidedata
asetrate guided sierpinski
asettb haas signalstats
ashowinfo haldclut signature
asidedata haldclutsrc silencedetect
asoftclip hdcd silenceremove
aspectralstats headphone sinc
asplit hflip sine
ass hflip_vulkan siti
astats highpass smartblur
astreamselect highshelf smptebars
asubboost hilbert smptehdbars
asubcut histeq sobel
asupercut histogram sobel_opencl
asuperpass hqdn3d sofalizer
asuperstop hqx spectrumsynth
atadenoise hstack speechnorm
atempo hsvhold split
atilt hsvkey spp
atrim hue sr
avectorscope huesaturation ssim
avgblur hwdownload stereo3d
avgblur_opencl hwmap stereotools
avgblur_vulkan hwupload stereowiden
avsynctest hwupload_cuda streamselect
axcorrelate hysteresis subtitles
azmq identity super2xsai
backgroundkey idet superequalizer
bandpass il surround
bandreject inflate swaprect
bass interlace swapuv
bbox interleave tblend
bench join telecine
bilateral kerndeint testsrc
bilateral_cuda kirsch testsrc2
biquad ladspa thistogram
bitplanenoise lagfun threshold
blackdetect latency thumbnail
blackframe lenscorrection thumbnail_cuda
blend lensfun tile
blend_vulkan libplacebo tiltshelf
blockdetect libvmaf tinterlace
blurdetect life tlut2
bm3d limitdiff tmedian
boxblur limiter tmidequalizer
boxblur_opencl loop tmix
bs2b loudnorm tonemap
bwdif lowpass tonemap_opencl
cas lowshelf tpad
cellauto lumakey transpose
channelmap lut transpose_opencl
channelsplit lut1d transpose_vulkan
chorus lut2 treble
chromaber_vulkan lut3d tremolo
chromahold lutrgb trim
chromakey lutyuv unpremultiply
chromakey_cuda mandelbrot unsharp
chromanr maskedclamp unsharp_opencl
chromashift maskedmax untile
ciescope maskedmerge v360
codecview maskedmin vaguedenoiser
color maskedthreshold varblur
colorbalance maskfun vectorscope
colorchannelmixer mcompand vflip
colorchart median vflip_vulkan
colorcontrast mergeplanes vfrdet
colorcorrect mestimate vibrance
colorhold metadata vibrato
colorize midequalizer vidstabdetect
colorkey minterpolate vidstabtransform
colorkey_opencl mix vif
colorlevels monochrome vignette
colormap morpho virtualbass
colormatrix movie vmafmotion
colorspace mpdecimate volume
colorspace_cuda mptestsrc volumedetect
colorspectrum msad vpp_qsv
colortemperature multiply vstack
compand negate w3fdif
compensationdelay nlmeans waveform
concat nlmeans_opencl weave
convolution nnedi xbr
convolution_opencl noformat xcorrelate
convolve noise xfade
copy normalize xfade_opencl
corr null xmedian
cover_rect nullsink xstack
crop nullsrc yadif
cropdetect openclsrc yadif_cuda
crossfeed oscilloscope yaepblur
crystalizer overlay yuvtestsrc
cue overlay_cuda zmq
curves overlay_opencl zoompan
datascope overlay_qsv zscale
dblur overlay_vulkan
dcshift owdenoise
Enabled bsfs:
aac_adtstoasc h264_redundant_pps pcm_rechunk
av1_frame_merge hapqa_extract pgs_frame_merge
av1_frame_split hevc_metadata prores_metadata
av1_metadata hevc_mp4toannexb remove_extradata
chomp imx_dump_header setts
dca_core mjpeg2jpeg text2movsub
dts2pts mjpega_dump_header trace_headers
dump_extradata mov2textsub truehd_core
dv_error_marker mp3_header_decompress vp9_metadata
eac3_core mpeg2_metadata vp9_raw_reorder
extract_extradata mpeg4_unpack_bframes vp9_superframe
filter_units noise vp9_superframe_split
h264_metadata null
h264_mp4toannexb opus_metadata
Enabled indevs:
dshow lavfi vfwcap
gdigrab libcdio
Enabled outdevs:
caca sdl2

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a.summary-letter {
text-decoration: none;
}
a {
color: #2D6198;
}
a:visited {
color: #884488;
}
#banner {
background-color: white;
position: relative;
text-align: center;
}
#banner img {
margin-bottom: 1px;
margin-top: 5px;
}
#body {
margin-left: 1em;
margin-right: 1em;
}
body {
background-color: #313131;
margin: 0;
text-align: justify;
}
.center {
margin-left: auto;
margin-right: auto;
text-align: center;
}
#container {
background-color: white;
color: #202020;
margin-left: 1em;
margin-right: 1em;
}
#footer {
text-align: center;
}
h1 a, h2 a, h3 a, h4 a {
text-decoration: inherit;
color: inherit;
}
h1, h2, h3, h4 {
padding-left: 0.4em;
border-radius: 4px;
padding-bottom: 0.25em;
padding-top: 0.25em;
border: 1px solid #6A996A;
}
h1 {
background-color: #7BB37B;
color: #151515;
font-size: 1.2em;
padding-bottom: 0.3em;
padding-top: 0.3em;
}
h2 {
color: #313131;
font-size: 1.0em;
background-color: #ABE3AB;
}
h3 {
color: #313131;
font-size: 0.9em;
margin-bottom: -6px;
background-color: #BBF3BB;
}
h4 {
color: #313131;
font-size: 0.8em;
margin-bottom: -8px;
background-color: #D1FDD1;
}
img {
border: 0;
}
#navbar {
background-color: #738073;
border-bottom: 1px solid #5C665C;
border-top: 1px solid #5C665C;
margin-top: 12px;
padding: 0.3em;
position: relative;
text-align: center;
}
#navbar a, #navbar_secondary a {
color: white;
padding: 0.3em;
text-decoration: none;
}
#navbar a:hover, #navbar_secondary a:hover {
background-color: #313131;
color: white;
text-decoration: none;
}
#navbar_secondary {
background-color: #738073;
border-bottom: 1px solid #5C665C;
border-left: 1px solid #5C665C;
border-right: 1px solid #5C665C;
padding: 0.3em;
position: relative;
text-align: center;
}
p {
margin-left: 1em;
margin-right: 1em;
}
pre {
margin-left: 3em;
margin-right: 3em;
padding: 0.3em;
border: 1px solid #bbb;
background-color: #f7f7f7;
}
dl dt {
font-weight: bold;
}
#proj_desc {
font-size: 1.2em;
}
#repos {
margin-left: 1em;
margin-right: 1em;
border-collapse: collapse;
border: solid 1px #6A996A;
}
#repos th {
background-color: #7BB37B;
border: solid 1px #6A996A;
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#repos td {
padding: 0.2em;
border: solid 1px #6A996A;
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<!-- Created by GNU Texinfo 6.8, https://www.gnu.org/software/texinfo/ -->
<head>
<meta charset="utf-8">
<title>
Developer Documentation
</title>
<meta name="viewport" content="width=device-width,initial-scale=1.0">
<link rel="stylesheet" type="text/css" href="bootstrap.min.css">
<link rel="stylesheet" type="text/css" href="style.min.css">
</head>
<body>
<div class="container">
<h1>
Developer Documentation
</h1>
<div align="center">
</div>
<a name="SEC_Top"></a>
<div class="Contents_element" id="SEC_Contents">
<h2 class="contents-heading">Table of Contents</h2>
<div class="contents">
<ul class="no-bullet">
<li><a id="toc-Introduction" href="#Introduction">1 Introduction</a>
<ul class="no-bullet">
<li><a id="toc-Contributing-code" href="#Contributing-code">1.1 Contributing code</a></li>
</ul></li>
<li><a id="toc-Coding-Rules-1" href="#Coding-Rules-1">2 Coding Rules</a>
<ul class="no-bullet">
<li><a id="toc-C-language-features" href="#C-language-features">2.1 C language features</a></li>
<li><a id="toc-Code-formatting-conventions" href="#Code-formatting-conventions">2.2 Code formatting conventions</a>
<ul class="no-bullet">
<li><a id="toc-Vim-configuration" href="#Vim-configuration">2.2.1 Vim configuration</a></li>
<li><a id="toc-Emacs-configuration" href="#Emacs-configuration">2.2.2 Emacs configuration</a></li>
</ul></li>
<li><a id="toc-Comments" href="#Comments">2.3 Comments</a></li>
<li><a id="toc-Naming-conventions" href="#Naming-conventions">2.4 Naming conventions</a></li>
<li><a id="toc-Miscellaneous-conventions" href="#Miscellaneous-conventions">2.5 Miscellaneous conventions</a></li>
</ul></li>
<li><a id="toc-Development-Policy-1" href="#Development-Policy-1">3 Development Policy</a>
<ul class="no-bullet">
<li><a id="toc-Patches_002fCommitting" href="#Patches_002fCommitting">3.1 Patches/Committing</a></li>
<li><a id="toc-Code" href="#Code">3.2 Code</a></li>
<li><a id="toc-Documentation_002fOther" href="#Documentation_002fOther">3.3 Documentation/Other</a></li>
</ul></li>
<li><a id="toc-Code-of-conduct" href="#Code-of-conduct">4 Code of conduct</a></li>
<li><a id="toc-Submitting-patches-1" href="#Submitting-patches-1">5 Submitting patches</a></li>
<li><a id="toc-New-codecs-or-formats-checklist" href="#New-codecs-or-formats-checklist">6 New codecs or formats checklist</a></li>
<li><a id="toc-Patch-submission-checklist" href="#Patch-submission-checklist">7 Patch submission checklist</a></li>
<li><a id="toc-Patch-review-process" href="#Patch-review-process">8 Patch review process</a></li>
<li><a id="toc-Regression-tests-1" href="#Regression-tests-1">9 Regression tests</a>
<ul class="no-bullet">
<li><a id="toc-Adding-files-to-the-fate_002dsuite-dataset" href="#Adding-files-to-the-fate_002dsuite-dataset">9.1 Adding files to the fate-suite dataset</a></li>
<li><a id="toc-Visualizing-Test-Coverage" href="#Visualizing-Test-Coverage">9.2 Visualizing Test Coverage</a></li>
<li><a id="toc-Using-Valgrind" href="#Using-Valgrind">9.3 Using Valgrind</a></li>
</ul></li>
<li><a id="toc-Release-process-1" href="#Release-process-1">10 Release process</a>
<ul class="no-bullet">
<li><a id="toc-Criteria-for-Point-Releases-1" href="#Criteria-for-Point-Releases-1">10.1 Criteria for Point Releases</a></li>
<li><a id="toc-Release-Checklist" href="#Release-Checklist">10.2 Release Checklist</a></li>
</ul></li>
</ul>
</div>
</div>
<a name="Introduction"></a>
<h2 class="chapter">1 Introduction<span class="pull-right"><a class="anchor hidden-xs" href="#Introduction" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Introduction" aria-hidden="true">TOC</a></span></h2>
<p>This text is concerned with the development <em>of</em> FFmpeg itself. Information
on using the FFmpeg libraries in other programs can be found elsewhere, e.g. in:
</p><ul>
<li> the installed header files
</li><li> <a href="http://ffmpeg.org/doxygen/trunk/index.html">the Doxygen documentation</a>
generated from the headers
</li><li> the examples under <samp>doc/examples</samp>
</li></ul>
<p>If you modify FFmpeg code for your own use case, you are highly encouraged to
<em>submit your changes back to us</em>, using this document as a guide. There are
both pragmatic and ideological reasons to do so:
</p><ul>
<li> Maintaining external changes to keep up with upstream development is
time-consuming and error-prone. With your code in the main tree, it will be
maintained by FFmpeg developers.
</li><li> FFmpeg developers include leading experts in the field who can find bugs or
design flaws in your code.
</li><li> By supporting the project you find useful you ensure it continues to be
maintained and developed.
</li></ul>
<p>For more detailed legal information about the use of FFmpeg in
external programs read the <samp>LICENSE</samp> file in the source tree and
consult <a href="https://ffmpeg.org/legal.html">https://ffmpeg.org/legal.html</a>.
</p>
<a name="Contributing-code"></a>
<h3 class="section">1.1 Contributing code<span class="pull-right"><a class="anchor hidden-xs" href="#Contributing-code" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Contributing-code" aria-hidden="true">TOC</a></span></h3>
<p>All proposed code changes should be submitted for review to
<a href="mailto:ffmpeg-devel@ffmpeg.org">the development mailing list</a>, as
described in more detail in the <a href="#Submitting-patches">Submitting patches</a> chapter. The code
should comply with the <a href="#Development-Policy">Development Policy</a> and follow the <a href="#Coding-Rules">Coding Rules</a>.
The developer making the commit and the author are responsible for their changes
and should try to fix issues their commit causes.
</p>
<span id="Coding-Rules"></span><a name="Coding-Rules-1"></a>
<h2 class="chapter">2 Coding Rules<span class="pull-right"><a class="anchor hidden-xs" href="#Coding-Rules-1" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Coding-Rules-1" aria-hidden="true">TOC</a></span></h2>
<a name="C-language-features"></a>
<h3 class="section">2.1 C language features<span class="pull-right"><a class="anchor hidden-xs" href="#C-language-features" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-C-language-features" aria-hidden="true">TOC</a></span></h3>
<p>FFmpeg is programmed in the ISO C99 language, extended with:
</p><ul>
<li> Atomic operations from C11 <samp>stdatomic.h</samp>. They are emulated on
architectures/compilers that do not support them, so all FFmpeg-internal code
may use atomics without any extra checks. However, <samp>stdatomic.h</samp> must not
be included in public headers, so they stay C99-compatible.
</li></ul>
<p>Compiler-specific extensions may be used with good reason, but must not be
depended on, i.e. the code must still compile and work with compilers lacking
the extension.
</p>
<p>The following C99 features must not be used anywhere in the codebase:
</p><ul>
<li> variable-length arrays;
</li><li> complex numbers;
</li><li> mixed statements and declarations.
</li></ul>
<a name="Code-formatting-conventions"></a>
<h3 class="section">2.2 Code formatting conventions<span class="pull-right"><a class="anchor hidden-xs" href="#Code-formatting-conventions" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Code-formatting-conventions" aria-hidden="true">TOC</a></span></h3>
<p>There are the following guidelines regarding the indentation in files:
</p>
<ul>
<li> Indent size is 4.
</li><li> The TAB character is forbidden outside of Makefiles as is any
form of trailing whitespace. Commits containing either will be
rejected by the git repository.
</li><li> You should try to limit your code lines to 80 characters; however, do so if
and only if this improves readability.
</li><li> K&amp;R coding style is used.
</li></ul>
<p>The presentation is one inspired by &rsquo;indent -i4 -kr -nut&rsquo;.
</p>
<a name="Vim-configuration"></a>
<h4 class="subsection">2.2.1 Vim configuration<span class="pull-right"><a class="anchor hidden-xs" href="#Vim-configuration" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Vim-configuration" aria-hidden="true">TOC</a></span></h4>
<p>In order to configure Vim to follow FFmpeg formatting conventions, paste
the following snippet into your <samp>.vimrc</samp>:
</p><div class="example">
<pre class="example">&quot; indentation rules for FFmpeg: 4 spaces, no tabs
set expandtab
set shiftwidth=4
set softtabstop=4
set cindent
set cinoptions=(0
&quot; Allow tabs in Makefiles.
autocmd FileType make,automake set noexpandtab shiftwidth=8 softtabstop=8
&quot; Trailing whitespace and tabs are forbidden, so highlight them.
highlight ForbiddenWhitespace ctermbg=red guibg=red
match ForbiddenWhitespace /\s\+$\|\t/
&quot; Do not highlight spaces at the end of line while typing on that line.
autocmd InsertEnter * match ForbiddenWhitespace /\t\|\s\+\%#\@&lt;!$/
</pre></div>
<a name="Emacs-configuration"></a>
<h4 class="subsection">2.2.2 Emacs configuration<span class="pull-right"><a class="anchor hidden-xs" href="#Emacs-configuration" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Emacs-configuration" aria-hidden="true">TOC</a></span></h4>
<p>For Emacs, add these roughly equivalent lines to your <samp>.emacs.d/init.el</samp>:
</p><div class="example lisp">
<pre class="lisp">(c-add-style &quot;ffmpeg&quot;
'(&quot;k&amp;r&quot;
(c-basic-offset . 4)
(indent-tabs-mode . nil)
(show-trailing-whitespace . t)
(c-offsets-alist
(statement-cont . (c-lineup-assignments +)))
)
)
(setq c-default-style &quot;ffmpeg&quot;)
</pre></div>
<a name="Comments"></a>
<h3 class="section">2.3 Comments<span class="pull-right"><a class="anchor hidden-xs" href="#Comments" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Comments" aria-hidden="true">TOC</a></span></h3>
<p>Use the JavaDoc/Doxygen format (see examples below) so that code documentation
can be generated automatically. All nontrivial functions should have a comment
above them explaining what the function does, even if it is just one sentence.
All structures and their member variables should be documented, too.
</p>
<p>Avoid Qt-style and similar Doxygen syntax with <code>!</code> in it, i.e. replace
<code>//!</code> with <code>///</code> and similar. Also @ syntax should be employed
for markup commands, i.e. use <code>@param</code> and not <code>\param</code>.
</p>
<div class="example">
<pre class="example">/**
* @file
* MPEG codec.
* @author ...
*/
/**
* Summary sentence.
* more text ...
* ...
*/
typedef struct Foobar {
int var1; /**&lt; var1 description */
int var2; ///&lt; var2 description
/** var3 description */
int var3;
} Foobar;
/**
* Summary sentence.
* more text ...
* ...
* @param my_parameter description of my_parameter
* @return return value description
*/
int myfunc(int my_parameter)
...
</pre></div>
<a name="Naming-conventions"></a>
<h3 class="section">2.4 Naming conventions<span class="pull-right"><a class="anchor hidden-xs" href="#Naming-conventions" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Naming-conventions" aria-hidden="true">TOC</a></span></h3>
<p>Names of functions, variables, and struct members must be lowercase, using
underscores (_) to separate words. For example, &lsquo;<samp>avfilter_get_video_buffer</samp>&rsquo;
is an acceptable function name and &lsquo;<samp>AVFilterGetVideo</samp>&rsquo; is not.
</p>
<p>Struct, union, enum, and typedeffed type names must use CamelCase. All structs
and unions should be typedeffed to the same name as the struct/union tag, e.g.
<code>typedef struct AVFoo { ... } AVFoo;</code>. Enums are typically not
typedeffed.
</p>
<p>Enumeration constants and macros must be UPPERCASE, except for macros
masquerading as functions, which should use the function naming convention.
</p>
<p>All identifiers in the libraries should be namespaced as follows:
</p><ul>
<li> No namespacing for identifiers with file and lower scope (e.g. local variables,
static functions), and struct and union members,
</li><li> The <code>ff_</code> prefix must be used for variables and functions visible outside
of file scope, but only used internally within a single library, e.g.
&lsquo;<samp>ff_w64_demuxer</samp>&rsquo;. This prevents name collisions when FFmpeg is statically
linked.
</li><li> For variables and functions visible outside of file scope, used internally
across multiple libraries, use <code>avpriv_</code> as prefix, for example,
&lsquo;<samp>avpriv_report_missing_feature</samp>&rsquo;.
</li><li> All other internal identifiers, like private type or macro names, should be
namespaced only to avoid possible internal conflicts. E.g. <code>H264_NAL_SPS</code>
vs. <code>HEVC_NAL_SPS</code>.
</li><li> Each library has its own prefix for public symbols, in addition to the
commonly used <code>av_</code> (<code>avformat_</code> for libavformat,
<code>avcodec_</code> for libavcodec, <code>swr_</code> for libswresample, etc).
Check the existing code and choose names accordingly.
</li><li> Other public identifiers (struct, union, enum, macro, type names) must use their
library&rsquo;s public prefix (<code>AV</code>, <code>Sws</code>, or <code>Swr</code>).
</li></ul>
<p>Furthermore, name space reserved for the system should not be invaded.
Identifiers ending in <code>_t</code> are reserved by
<a href="http://pubs.opengroup.org/onlinepubs/007904975/functions/xsh_chap02_02.html#tag_02_02_02">POSIX</a>.
Also avoid names starting with <code>__</code> or <code>_</code> followed by an uppercase
letter as they are reserved by the C standard. Names starting with <code>_</code>
are reserved at the file level and may not be used for externally visible
symbols. If in doubt, just avoid names starting with <code>_</code> altogether.
</p>
<a name="Miscellaneous-conventions"></a>
<h3 class="section">2.5 Miscellaneous conventions<span class="pull-right"><a class="anchor hidden-xs" href="#Miscellaneous-conventions" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Miscellaneous-conventions" aria-hidden="true">TOC</a></span></h3>
<ul>
<li> fprintf and printf are forbidden in libavformat and libavcodec,
please use av_log() instead.
</li><li> Casts should be used only when necessary. Unneeded parentheses
should also be avoided if they don&rsquo;t make the code easier to understand.
</li></ul>
<span id="Development-Policy"></span><a name="Development-Policy-1"></a>
<h2 class="chapter">3 Development Policy<span class="pull-right"><a class="anchor hidden-xs" href="#Development-Policy-1" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Development-Policy-1" aria-hidden="true">TOC</a></span></h2>
<a name="Patches_002fCommitting"></a>
<h3 class="section">3.1 Patches/Committing<span class="pull-right"><a class="anchor hidden-xs" href="#Patches_002fCommitting" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Patches_002fCommitting" aria-hidden="true">TOC</a></span></h3>
<a name="Licenses-for-patches-must-be-compatible-with-FFmpeg_002e"></a>
<p>Contributions should be licensed under the
<a href="http://www.gnu.org/licenses/lgpl-2.1.html">LGPL 2.1</a>,
including an &quot;or any later version&quot; clause, or, if you prefer
a gift-style license, the
<a href="http://opensource.org/licenses/isc-license.txt">ISC</a> or
<a href="http://mit-license.org/">MIT</a> license.
<a href="http://www.gnu.org/licenses/gpl-2.0.html">GPL 2</a> including
an &quot;or any later version&quot; clause is also acceptable, but LGPL is
preferred.
If you add a new file, give it a proper license header. Do not copy and
paste it from a random place, use an existing file as template.
</p>
<a name="You-must-not-commit-code-which-breaks-FFmpeg_0021"></a>
<p>This means unfinished code which is enabled and breaks compilation,
or compiles but does not work/breaks the regression tests. Code which
is unfinished but disabled may be permitted under-circumstances, like
missing samples or an implementation with a small subset of features.
Always check the mailing list for any reviewers with issues and test
FATE before you push.
</p>
<a name="Keep-the-main-commit-message-short-with-an-extended-description-below_002e"></a>
<p>The commit message should have a short first line in the form of
a &lsquo;<samp>topic: short description</samp>&rsquo; as a header, separated by a newline
from the body consisting of an explanation of why the change is necessary.
If the commit fixes a known bug on the bug tracker, the commit message
should include its bug ID. Referring to the issue on the bug tracker does
not exempt you from writing an excerpt of the bug in the commit message.
</p>
<a name="Testing-must-be-adequate-but-not-excessive_002e"></a>
<p>If it works for you, others, and passes FATE then it should be OK to commit
it, provided it fits the other committing criteria. You should not worry about
over-testing things. If your code has problems (portability, triggers
compiler bugs, unusual environment etc) they will be reported and eventually
fixed.
</p>
<a name="Do-not-commit-unrelated-changes-together_002e"></a>
<p>They should be split them into self-contained pieces. Also do not forget
that if part B depends on part A, but A does not depend on B, then A can
and should be committed first and separate from B. Keeping changes well
split into self-contained parts makes reviewing and understanding them on
the commit log mailing list easier. This also helps in case of debugging
later on.
Also if you have doubts about splitting or not splitting, do not hesitate to
ask/discuss it on the developer mailing list.
</p>
<a name="Ask-before-you-change-the-build-system-_0028configure_002c-etc_0029_002e"></a>
<p>Do not commit changes to the build system (Makefiles, configure script)
which change behavior, defaults etc, without asking first. The same
applies to compiler warning fixes, trivial looking fixes and to code
maintained by other developers. We usually have a reason for doing things
the way we do. Send your changes as patches to the ffmpeg-devel mailing
list, and if the code maintainers say OK, you may commit. This does not
apply to files you wrote and/or maintain.
</p>
<a name="Cosmetic-changes-should-be-kept-in-separate-patches_002e"></a>
<p>We refuse source indentation and other cosmetic changes if they are mixed
with functional changes, such commits will be rejected and removed. Every
developer has his own indentation style, you should not change it. Of course
if you (re)write something, you can use your own style, even though we would
prefer if the indentation throughout FFmpeg was consistent (Many projects
force a given indentation style - we do not.). If you really need to make
indentation changes (try to avoid this), separate them strictly from real
changes.
</p>
<p>NOTE: If you had to put if(){ .. } over a large (&gt; 5 lines) chunk of code,
then either do NOT change the indentation of the inner part within (do not
move it to the right)! or do so in a separate commit
</p>
<a name="Commit-messages-should-always-be-filled-out-properly_002e"></a>
<p>Always fill out the commit log message. Describe in a few lines what you
changed and why. You can refer to mailing list postings if you fix a
particular bug. Comments such as &quot;fixed!&quot; or &quot;Changed it.&quot; are unacceptable.
Recommended format:
</p>
<div class="example">
<pre class="example">area changed: Short 1 line description
details describing what and why and giving references.
</pre></div>
<a name="Credit-the-author-of-the-patch_002e"></a>
<p>Make sure the author of the commit is set correctly. (see git commit &ndash;author)
If you apply a patch, send an
answer to ffmpeg-devel (or wherever you got the patch from) saying that
you applied the patch.
</p>
<a name="Complex-patches-should-refer-to-discussion-surrounding-them_002e"></a>
<p>When applying patches that have been discussed (at length) on the mailing
list, reference the thread in the log message.
</p>
<a name="Always-wait-long-enough-before-pushing-changes"></a>
<p>Do NOT commit to code actively maintained by others without permission.
Send a patch to ffmpeg-devel. If no one answers within a reasonable
time-frame (12h for build failures and security fixes, 3 days small changes,
1 week for big patches) then commit your patch if you think it is OK.
Also note, the maintainer can simply ask for more time to review!
</p>
<a name="Code"></a>
<h3 class="section">3.2 Code<span class="pull-right"><a class="anchor hidden-xs" href="#Code" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Code" aria-hidden="true">TOC</a></span></h3>
<a name="API_002fABI-changes-should-be-discussed-before-they-are-made_002e"></a>
<p>Do not change behavior of the programs (renaming options etc) or public
API or ABI without first discussing it on the ffmpeg-devel mailing list.
Do not remove widely used functionality or features (redundant code can be removed).
</p>
<a name="Remember-to-check-if-you-need-to-bump-versions-for-libav_002a_002e"></a>
<p>Depending on the change, you may need to change the version integer.
Incrementing the first component means no backward compatibility to
previous versions (e.g. removal of a function from the public API).
Incrementing the second component means backward compatible change
(e.g. addition of a function to the public API or extension of an
existing data structure).
Incrementing the third component means a noteworthy binary compatible
change (e.g. encoder bug fix that matters for the decoder). The third
component always starts at 100 to distinguish FFmpeg from Libav.
</p>
<a name="Warnings-for-correct-code-may-be-disabled-if-there-is-no-other-option_002e"></a>
<p>Compiler warnings indicate potential bugs or code with bad style. If a type of
warning always points to correct and clean code, that warning should
be disabled, not the code changed.
Thus the remaining warnings can either be bugs or correct code.
If it is a bug, the bug has to be fixed. If it is not, the code should
be changed to not generate a warning unless that causes a slowdown
or obfuscates the code.
</p>
<a name="Check-untrusted-input-properly_002e"></a>
<p>Never write to unallocated memory, never write over the end of arrays,
always check values read from some untrusted source before using them
as array index or other risky things.
</p>
<a name="Documentation_002fOther"></a>
<h3 class="section">3.3 Documentation/Other<span class="pull-right"><a class="anchor hidden-xs" href="#Documentation_002fOther" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Documentation_002fOther" aria-hidden="true">TOC</a></span></h3>
<a name="Subscribe-to-the-ffmpeg_002ddevel-mailing-list_002e"></a>
<p>It is important to be subscribed to the
<a href="https://lists.ffmpeg.org/mailman/listinfo/ffmpeg-devel">ffmpeg-devel</a>
mailing list. Almost any non-trivial patch is to be sent there for review.
Other developers may have comments about your contribution. We expect you see
those comments, and to improve it if requested. (N.B. Experienced committers
have other channels, and may sometimes skip review for trivial fixes.) Also,
discussion here about bug fixes and FFmpeg improvements by other developers may
be helpful information for you. Finally, by being a list subscriber, your
contribution will be posted immediately to the list, without the moderation
hold which messages from non-subscribers experience.
</p>
<p>However, it is more important to the project that we receive your patch than
that you be subscribed to the ffmpeg-devel list. If you have a patch, and don&rsquo;t
want to subscribe and discuss the patch, then please do send it to the list
anyway.
</p>
<a name="Subscribe-to-the-ffmpeg_002dcvslog-mailing-list_002e"></a>
<p>Diffs of all commits are sent to the
<a href="https://lists.ffmpeg.org/mailman/listinfo/ffmpeg-cvslog">ffmpeg-cvslog</a>
mailing list. Some developers read this list to review all code base changes
from all sources. Subscribing to this list is not mandatory.
</p>
<a name="Keep-the-documentation-up-to-date_002e"></a>
<p>Update the documentation if you change behavior or add features. If you are
unsure how best to do this, send a patch to ffmpeg-devel, the documentation
maintainer(s) will review and commit your stuff.
</p>
<a name="Important-discussions-should-be-accessible-to-all_002e"></a>
<p>Try to keep important discussions and requests (also) on the public
developer mailing list, so that all developers can benefit from them.
</p>
<a name="Check-your-entries-in-MAINTAINERS_002e"></a>
<p>Make sure that no parts of the codebase that you maintain are missing from the
<samp>MAINTAINERS</samp> file. If something that you want to maintain is missing add it with
your name after it.
If at some point you no longer want to maintain some code, then please help in
finding a new maintainer and also don&rsquo;t forget to update the <samp>MAINTAINERS</samp> file.
</p>
<p>We think our rules are not too hard. If you have comments, contact us.
</p>
<a name="Code-of-conduct"></a>
<h2 class="chapter">4 Code of conduct<span class="pull-right"><a class="anchor hidden-xs" href="#Code-of-conduct" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Code-of-conduct" aria-hidden="true">TOC</a></span></h2>
<p>Be friendly and respectful towards others and third parties.
Treat others the way you yourself want to be treated.
</p>
<p>Be considerate. Not everyone shares the same viewpoint and priorities as you do.
Different opinions and interpretations help the project.
Looking at issues from a different perspective assists development.
</p>
<p>Do not assume malice for things that can be attributed to incompetence. Even if
it is malice, it&rsquo;s rarely good to start with that as initial assumption.
</p>
<p>Stay friendly even if someone acts contrarily. Everyone has a bad day
once in a while.
If you yourself have a bad day or are angry then try to take a break and reply
once you are calm and without anger if you have to.
</p>
<p>Try to help other team members and cooperate if you can.
</p>
<p>The goal of software development is to create technical excellence, not for any
individual to be better and &quot;win&quot; against the others. Large software projects
are only possible and successful through teamwork.
</p>
<p>If someone struggles do not put them down. Give them a helping hand
instead and point them in the right direction.
</p>
<p>Finally, keep in mind the immortal words of Bill and Ted,
&quot;Be excellent to each other.&quot;
</p>
<span id="Submitting-patches"></span><a name="Submitting-patches-1"></a>
<h2 class="chapter">5 Submitting patches<span class="pull-right"><a class="anchor hidden-xs" href="#Submitting-patches-1" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Submitting-patches-1" aria-hidden="true">TOC</a></span></h2>
<p>First, read the <a href="#Coding-Rules">Coding Rules</a> above if you did not yet, in particular
the rules regarding patch submission.
</p>
<p>When you submit your patch, please use <code>git format-patch</code> or
<code>git send-email</code>. We cannot read other diffs :-).
</p>
<p>Also please do not submit a patch which contains several unrelated changes.
Split it into separate, self-contained pieces. This does not mean splitting
file by file. Instead, make the patch as small as possible while still
keeping it as a logical unit that contains an individual change, even
if it spans multiple files. This makes reviewing your patches much easier
for us and greatly increases your chances of getting your patch applied.
</p>
<p>Use the patcheck tool of FFmpeg to check your patch.
The tool is located in the tools directory.
</p>
<p>Run the <a href="#Regression-tests">Regression tests</a> before submitting a patch in order to verify
it does not cause unexpected problems.
</p>
<p>It also helps quite a bit if you tell us what the patch does (for example
&rsquo;replaces lrint by lrintf&rsquo;), and why (for example &rsquo;*BSD isn&rsquo;t C99 compliant
and has no lrint()&rsquo;)
</p>
<p>Also please if you send several patches, send each patch as a separate mail,
do not attach several unrelated patches to the same mail.
</p>
<p>Patches should be posted to the
<a href="https://lists.ffmpeg.org/mailman/listinfo/ffmpeg-devel">ffmpeg-devel</a>
mailing list. Use <code>git send-email</code> when possible since it will properly
send patches without requiring extra care. If you cannot, then send patches
as base64-encoded attachments, so your patch is not trashed during
transmission. Also ensure the correct mime type is used
(text/x-diff or text/x-patch or at least text/plain) and that only one
patch is inline or attached per mail.
You can check <a href="https://patchwork.ffmpeg.org">https://patchwork.ffmpeg.org</a>, if your patch does not show up, its mime type
likely was wrong.
</p>
<a name="Sending-patches-from-email-clients"></a>
<p>Using <code>git send-email</code> might not be desirable for everyone. The
following trick allows to send patches via email clients in a safe
way. It has been tested with Outlook and Thunderbird (with X-Unsent
extension) and might work with other applications.
</p>
<p>Create your patch like this:
</p>
<pre class="verbatim">git format-patch -s -o &quot;outputfolder&quot; --add-header &quot;X-Unsent: 1&quot; --suffix .eml --to ffmpeg-devel@ffmpeg.org -1 1a2b3c4d
</pre>
<p>Now you&rsquo;ll just need to open the eml file with the email application
and execute &rsquo;Send&rsquo;.
</p>
<a name="Reviews"></a>
<p>Your patch will be reviewed on the mailing list. You will likely be asked
to make some changes and are expected to send in an improved version that
incorporates the requests from the review. This process may go through
several iterations. Once your patch is deemed good enough, some developer
will pick it up and commit it to the official FFmpeg tree.
</p>
<p>Give us a few days to react. But if some time passes without reaction,
send a reminder by email. Your patch should eventually be dealt with.
</p>
<a name="New-codecs-or-formats-checklist"></a>
<h2 class="chapter">6 New codecs or formats checklist<span class="pull-right"><a class="anchor hidden-xs" href="#New-codecs-or-formats-checklist" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-New-codecs-or-formats-checklist" aria-hidden="true">TOC</a></span></h2>
<ol>
<li> Did you use av_cold for codec initialization and close functions?
</li><li> Did you add a long_name under NULL_IF_CONFIG_SMALL to the AVCodec or
AVInputFormat/AVOutputFormat struct?
</li><li> Did you bump the minor version number (and reset the micro version
number) in <samp>libavcodec/version.h</samp> or <samp>libavformat/version.h</samp>?
</li><li> Did you register it in <samp>allcodecs.c</samp> or <samp>allformats.c</samp>?
</li><li> Did you add the AVCodecID to <samp>avcodec.h</samp>?
When adding new codec IDs, also add an entry to the codec descriptor
list in <samp>libavcodec/codec_desc.c</samp>.
</li><li> If it has a FourCC, did you add it to <samp>libavformat/riff.c</samp>,
even if it is only a decoder?
</li><li> Did you add a rule to compile the appropriate files in the Makefile?
Remember to do this even if you&rsquo;re just adding a format to a file that is
already being compiled by some other rule, like a raw demuxer.
</li><li> Did you add an entry to the table of supported formats or codecs in
<samp>doc/general.texi</samp>?
</li><li> Did you add an entry in the Changelog?
</li><li> If it depends on a parser or a library, did you add that dependency in
configure?
</li><li> Did you <code>git add</code> the appropriate files before committing?
</li><li> Did you make sure it compiles standalone, i.e. with
<code>configure --disable-everything --enable-decoder=foo</code>
(or <code>--enable-demuxer</code> or whatever your component is)?
</li></ol>
<a name="Patch-submission-checklist"></a>
<h2 class="chapter">7 Patch submission checklist<span class="pull-right"><a class="anchor hidden-xs" href="#Patch-submission-checklist" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Patch-submission-checklist" aria-hidden="true">TOC</a></span></h2>
<ol>
<li> Does <code>make fate</code> pass with the patch applied?
</li><li> Was the patch generated with git format-patch or send-email?
</li><li> Did you sign-off your patch? (<code>git commit -s</code>)
See <a href="https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/plain/Documentation/process/submitting-patches.rst">Sign your work</a> for the meaning
of <em>sign-off</em>.
</li><li> Did you provide a clear git commit log message?
</li><li> Is the patch against latest FFmpeg git master branch?
</li><li> Are you subscribed to ffmpeg-devel?
(the list is subscribers only due to spam)
</li><li> Have you checked that the changes are minimal, so that the same cannot be
achieved with a smaller patch and/or simpler final code?
</li><li> If the change is to speed critical code, did you benchmark it?
</li><li> If you did any benchmarks, did you provide them in the mail?
</li><li> Have you checked that the patch does not introduce buffer overflows or
other security issues?
</li><li> Did you test your decoder or demuxer against damaged data? If no, see
tools/trasher, the noise bitstream filter, and
<a href="http://caca.zoy.org/wiki/zzuf">zzuf</a>. Your decoder or demuxer
should not crash, end in a (near) infinite loop, or allocate ridiculous
amounts of memory when fed damaged data.
</li><li> Did you test your decoder or demuxer against sample files?
Samples may be obtained at <a href="https://samples.ffmpeg.org">https://samples.ffmpeg.org</a>.
</li><li> Does the patch not mix functional and cosmetic changes?
</li><li> Did you add tabs or trailing whitespace to the code? Both are forbidden.
</li><li> Is the patch attached to the email you send?
</li><li> Is the mime type of the patch correct? It should be text/x-diff or
text/x-patch or at least text/plain and not application/octet-stream.
</li><li> If the patch fixes a bug, did you provide a verbose analysis of the bug?
</li><li> If the patch fixes a bug, did you provide enough information, including
a sample, so the bug can be reproduced and the fix can be verified?
Note please do not attach samples &gt;100k to mails but rather provide a
URL, you can upload to <a href="https://streams.videolan.org/upload/">https://streams.videolan.org/upload/</a>.
</li><li> Did you provide a verbose summary about what the patch does change?
</li><li> Did you provide a verbose explanation why it changes things like it does?
</li><li> Did you provide a verbose summary of the user visible advantages and
disadvantages if the patch is applied?
</li><li> Did you provide an example so we can verify the new feature added by the
patch easily?
</li><li> If you added a new file, did you insert a license header? It should be
taken from FFmpeg, not randomly copied and pasted from somewhere else.
</li><li> You should maintain alphabetical order in alphabetically ordered lists as
long as doing so does not break API/ABI compatibility.
</li><li> Lines with similar content should be aligned vertically when doing so
improves readability.
</li><li> Consider adding a regression test for your code.
</li><li> If you added YASM code please check that things still work with &ndash;disable-yasm.
</li><li> Make sure you check the return values of function and return appropriate
error codes. Especially memory allocation functions like <code>av_malloc()</code>
are notoriously left unchecked, which is a serious problem.
</li><li> Test your code with valgrind and or Address Sanitizer to ensure it&rsquo;s free
of leaks, out of array accesses, etc.
</li></ol>
<a name="Patch-review-process"></a>
<h2 class="chapter">8 Patch review process<span class="pull-right"><a class="anchor hidden-xs" href="#Patch-review-process" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Patch-review-process" aria-hidden="true">TOC</a></span></h2>
<p>All patches posted to ffmpeg-devel will be reviewed, unless they contain a
clear note that the patch is not for the git master branch.
Reviews and comments will be posted as replies to the patch on the
mailing list. The patch submitter then has to take care of every comment,
that can be by resubmitting a changed patch or by discussion. Resubmitted
patches will themselves be reviewed like any other patch. If at some point
a patch passes review with no comments then it is approved, that can for
simple and small patches happen immediately while large patches will generally
have to be changed and reviewed many times before they are approved.
After a patch is approved it will be committed to the repository.
</p>
<p>We will review all submitted patches, but sometimes we are quite busy so
especially for large patches this can take several weeks.
</p>
<p>If you feel that the review process is too slow and you are willing to try to
take over maintainership of the area of code you change then just clone
git master and maintain the area of code there. We will merge each area from
where its best maintained.
</p>
<p>When resubmitting patches, please do not make any significant changes
not related to the comments received during review. Such patches will
be rejected. Instead, submit significant changes or new features as
separate patches.
</p>
<p>Everyone is welcome to review patches. Also if you are waiting for your patch
to be reviewed, please consider helping to review other patches, that is a great
way to get everyone&rsquo;s patches reviewed sooner.
</p>
<span id="Regression-tests"></span><a name="Regression-tests-1"></a>
<h2 class="chapter">9 Regression tests<span class="pull-right"><a class="anchor hidden-xs" href="#Regression-tests-1" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Regression-tests-1" aria-hidden="true">TOC</a></span></h2>
<p>Before submitting a patch (or committing to the repository), you should at least
test that you did not break anything.
</p>
<p>Running &rsquo;make fate&rsquo; accomplishes this, please see <a href="fate.html">fate.html</a> for details.
</p>
<p>[Of course, some patches may change the results of the regression tests. In
this case, the reference results of the regression tests shall be modified
accordingly].
</p>
<a name="Adding-files-to-the-fate_002dsuite-dataset"></a>
<h3 class="section">9.1 Adding files to the fate-suite dataset<span class="pull-right"><a class="anchor hidden-xs" href="#Adding-files-to-the-fate_002dsuite-dataset" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Adding-files-to-the-fate_002dsuite-dataset" aria-hidden="true">TOC</a></span></h3>
<p>When there is no muxer or encoder available to generate test media for a
specific test then the media has to be included in the fate-suite.
First please make sure that the sample file is as small as possible to test the
respective decoder or demuxer sufficiently. Large files increase network
bandwidth and disk space requirements.
Once you have a working fate test and fate sample, provide in the commit
message or introductory message for the patch series that you post to
the ffmpeg-devel mailing list, a direct link to download the sample media.
</p>
<a name="Visualizing-Test-Coverage"></a>
<h3 class="section">9.2 Visualizing Test Coverage<span class="pull-right"><a class="anchor hidden-xs" href="#Visualizing-Test-Coverage" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Visualizing-Test-Coverage" aria-hidden="true">TOC</a></span></h3>
<p>The FFmpeg build system allows visualizing the test coverage in an easy
manner with the coverage tools <code>gcov</code>/<code>lcov</code>. This involves
the following steps:
</p>
<ol>
<li> Configure to compile with instrumentation enabled:
<code>configure --toolchain=gcov</code>.
</li><li> Run your test case, either manually or via FATE. This can be either
the full FATE regression suite, or any arbitrary invocation of any
front-end tool provided by FFmpeg, in any combination.
</li><li> Run <code>make lcov</code> to generate coverage data in HTML format.
</li><li> View <code>lcov/index.html</code> in your preferred HTML viewer.
</li></ol>
<p>You can use the command <code>make lcov-reset</code> to reset the coverage
measurements. You will need to rerun <code>make lcov</code> after running a
new test.
</p>
<a name="Using-Valgrind"></a>
<h3 class="section">9.3 Using Valgrind<span class="pull-right"><a class="anchor hidden-xs" href="#Using-Valgrind" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Using-Valgrind" aria-hidden="true">TOC</a></span></h3>
<p>The configure script provides a shortcut for using valgrind to spot bugs
related to memory handling. Just add the option
<code>--toolchain=valgrind-memcheck</code> or <code>--toolchain=valgrind-massif</code>
to your configure line, and reasonable defaults will be set for running
FATE under the supervision of either the <strong>memcheck</strong> or the
<strong>massif</strong> tool of the valgrind suite.
</p>
<p>In case you need finer control over how valgrind is invoked, use the
<code>--target-exec='valgrind &lt;your_custom_valgrind_options&gt;</code> option in
your configure line instead.
</p>
<span id="Release-process"></span><a name="Release-process-1"></a>
<h2 class="chapter">10 Release process<span class="pull-right"><a class="anchor hidden-xs" href="#Release-process-1" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Release-process-1" aria-hidden="true">TOC</a></span></h2>
<p>FFmpeg maintains a set of <strong>release branches</strong>, which are the
recommended deliverable for system integrators and distributors (such as
Linux distributions, etc.). At regular times, a <strong>release
manager</strong> prepares, tests and publishes tarballs on the
<a href="https://ffmpeg.org">https://ffmpeg.org</a> website.
</p>
<p>There are two kinds of releases:
</p>
<ol>
<li> <strong>Major releases</strong> always include the latest and greatest
features and functionality.
</li><li> <strong>Point releases</strong> are cut from <strong>release</strong> branches,
which are named <code>release/X</code>, with <code>X</code> being the release
version number.
</li></ol>
<p>Note that we promise to our users that shared libraries from any FFmpeg
release never break programs that have been <strong>compiled</strong> against
previous versions of <strong>the same release series</strong> in any case!
</p>
<p>However, from time to time, we do make API changes that require adaptations
in applications. Such changes are only allowed in (new) major releases and
require further steps such as bumping library version numbers and/or
adjustments to the symbol versioning file. Please discuss such changes
on the <strong>ffmpeg-devel</strong> mailing list in time to allow forward planning.
</p>
<span id="Criteria-for-Point-Releases"></span><a name="Criteria-for-Point-Releases-1"></a>
<h3 class="section">10.1 Criteria for Point Releases<span class="pull-right"><a class="anchor hidden-xs" href="#Criteria-for-Point-Releases-1" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Criteria-for-Point-Releases-1" aria-hidden="true">TOC</a></span></h3>
<p>Changes that match the following criteria are valid candidates for
inclusion into a point release:
</p>
<ol>
<li> Fixes a security issue, preferably identified by a <strong>CVE
number</strong> issued by <a href="http://cve.mitre.org/">http://cve.mitre.org/</a>.
</li><li> Fixes a documented bug in <a href="https://trac.ffmpeg.org">https://trac.ffmpeg.org</a>.
</li><li> Improves the included documentation.
</li><li> Retains both source code and binary compatibility with previous
point releases of the same release branch.
</li></ol>
<p>The order for checking the rules is (1 OR 2 OR 3) AND 4.
</p>
<a name="Release-Checklist"></a>
<h3 class="section">10.2 Release Checklist<span class="pull-right"><a class="anchor hidden-xs" href="#Release-Checklist" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Release-Checklist" aria-hidden="true">TOC</a></span></h3>
<p>The release process involves the following steps:
</p>
<ol>
<li> Ensure that the <samp>RELEASE</samp> file contains the version number for
the upcoming release.
</li><li> Add the release at <a href="https://trac.ffmpeg.org/admin/ticket/versions">https://trac.ffmpeg.org/admin/ticket/versions</a>.
</li><li> Announce the intent to do a release to the mailing list.
</li><li> Make sure all relevant security fixes have been backported. See
<a href="https://ffmpeg.org/security.html">https://ffmpeg.org/security.html</a>.
</li><li> Ensure that the FATE regression suite still passes in the release
branch on at least <strong>i386</strong> and <strong>amd64</strong>
(cf. <a href="#Regression-tests">Regression tests</a>).
</li><li> Prepare the release tarballs in <code>bz2</code> and <code>gz</code> formats, and
supplementing files that contain <code>gpg</code> signatures
</li><li> Publish the tarballs at <a href="https://ffmpeg.org/releases">https://ffmpeg.org/releases</a>. Create and
push an annotated tag in the form <code>nX</code>, with <code>X</code>
containing the version number.
</li><li> Propose and send a patch to the <strong>ffmpeg-devel</strong> mailing list
with a news entry for the website.
</li><li> Publish the news entry.
</li><li> Send an announcement to the mailing list.
</li></ol>
<p style="font-size: small;">
This document was generated using <a href="https://www.gnu.org/software/texinfo/"><em>makeinfo</em></a>.
</p>
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<div class="Contents_element" id="SEC_Contents">
<h2 class="contents-heading">Table of Contents</h2>
<div class="contents">
<ul class="no-bullet">
<li><a id="toc-General-Questions" href="#General-Questions">1 General Questions</a>
<ul class="no-bullet">
<li><a id="toc-Why-doesn_0027t-FFmpeg-support-feature-_005bxyz_005d_003f" href="#Why-doesn_0027t-FFmpeg-support-feature-_005bxyz_005d_003f">1.1 Why doesn&rsquo;t FFmpeg support feature [xyz]?</a></li>
<li><a id="toc-FFmpeg-does-not-support-codec-XXX_002e-Can-you-include-a-Windows-DLL-loader-to-support-it_003f" href="#FFmpeg-does-not-support-codec-XXX_002e-Can-you-include-a-Windows-DLL-loader-to-support-it_003f">1.2 FFmpeg does not support codec XXX. Can you include a Windows DLL loader to support it?</a></li>
<li><a id="toc-I-cannot-read-this-file-although-this-format-seems-to-be-supported-by-ffmpeg_002e" href="#I-cannot-read-this-file-although-this-format-seems-to-be-supported-by-ffmpeg_002e">1.3 I cannot read this file although this format seems to be supported by ffmpeg.</a></li>
<li><a id="toc-Which-codecs-are-supported-by-Windows_003f" href="#Which-codecs-are-supported-by-Windows_003f">1.4 Which codecs are supported by Windows?</a></li>
</ul></li>
<li><a id="toc-Compilation" href="#Compilation">2 Compilation</a>
<ul class="no-bullet">
<li><a id="toc-error_003a-can_0027t-find-a-register-in-class-_0027GENERAL_005fREGS_0027-while-reloading-_0027asm_0027" href="#error_003a-can_0027t-find-a-register-in-class-_0027GENERAL_005fREGS_0027-while-reloading-_0027asm_0027">2.1 <code>error: can't find a register in class 'GENERAL_REGS' while reloading 'asm'</code></a></li>
<li><a id="toc-I-have-installed-this-library-with-my-distro_0027s-package-manager_002e-Why-does-configure-not-see-it_003f" href="#I-have-installed-this-library-with-my-distro_0027s-package-manager_002e-Why-does-configure-not-see-it_003f">2.2 I have installed this library with my distro&rsquo;s package manager. Why does <code>configure</code> not see it?</a></li>
<li><a id="toc-How-do-I-make-pkg_002dconfig-find-my-libraries_003f" href="#How-do-I-make-pkg_002dconfig-find-my-libraries_003f">2.3 How do I make <code>pkg-config</code> find my libraries?</a></li>
<li><a id="toc-How-do-I-use-pkg_002dconfig-when-cross_002dcompiling_003f" href="#How-do-I-use-pkg_002dconfig-when-cross_002dcompiling_003f">2.4 How do I use <code>pkg-config</code> when cross-compiling?</a></li>
</ul></li>
<li><a id="toc-Usage" href="#Usage">3 Usage</a>
<ul class="no-bullet">
<li><a id="toc-ffmpeg-does-not-work_003b-what-is-wrong_003f" href="#ffmpeg-does-not-work_003b-what-is-wrong_003f">3.1 ffmpeg does not work; what is wrong?</a></li>
<li><a id="toc-How-do-I-encode-single-pictures-into-movies_003f" href="#How-do-I-encode-single-pictures-into-movies_003f">3.2 How do I encode single pictures into movies?</a></li>
<li><a id="toc-How-do-I-encode-movie-to-single-pictures_003f" href="#How-do-I-encode-movie-to-single-pictures_003f">3.3 How do I encode movie to single pictures?</a></li>
<li><a id="toc-Why-do-I-see-a-slight-quality-degradation-with-multithreaded-MPEG_002a-encoding_003f" href="#Why-do-I-see-a-slight-quality-degradation-with-multithreaded-MPEG_002a-encoding_003f">3.4 Why do I see a slight quality degradation with multithreaded MPEG* encoding?</a></li>
<li><a id="toc-How-can-I-read-from-the-standard-input-or-write-to-the-standard-output_003f" href="#How-can-I-read-from-the-standard-input-or-write-to-the-standard-output_003f">3.5 How can I read from the standard input or write to the standard output?</a></li>
<li><a id="toc-_002df-jpeg-doesn_0027t-work_002e" href="#g_t_002df-jpeg-doesn_0027t-work_002e">3.6 -f jpeg doesn&rsquo;t work.</a></li>
<li><a id="toc-Why-can-I-not-change-the-frame-rate_003f" href="#Why-can-I-not-change-the-frame-rate_003f">3.7 Why can I not change the frame rate?</a></li>
<li><a id="toc-How-do-I-encode-Xvid-or-DivX-video-with-ffmpeg_003f" href="#How-do-I-encode-Xvid-or-DivX-video-with-ffmpeg_003f">3.8 How do I encode Xvid or DivX video with ffmpeg?</a></li>
<li><a id="toc-Which-are-good-parameters-for-encoding-high-quality-MPEG_002d4_003f" href="#Which-are-good-parameters-for-encoding-high-quality-MPEG_002d4_003f">3.9 Which are good parameters for encoding high quality MPEG-4?</a></li>
<li><a id="toc-Which-are-good-parameters-for-encoding-high-quality-MPEG_002d1_002fMPEG_002d2_003f" href="#Which-are-good-parameters-for-encoding-high-quality-MPEG_002d1_002fMPEG_002d2_003f">3.10 Which are good parameters for encoding high quality MPEG-1/MPEG-2?</a></li>
<li><a id="toc-Interlaced-video-looks-very-bad-when-encoded-with-ffmpeg_002c-what-is-wrong_003f" href="#Interlaced-video-looks-very-bad-when-encoded-with-ffmpeg_002c-what-is-wrong_003f">3.11 Interlaced video looks very bad when encoded with ffmpeg, what is wrong?</a></li>
<li><a id="toc-How-can-I-read-DirectShow-files_003f" href="#How-can-I-read-DirectShow-files_003f">3.12 How can I read DirectShow files?</a></li>
<li><a id="toc-How-can-I-join-video-files_003f" href="#How-can-I-join-video-files_003f">3.13 How can I join video files?</a></li>
<li><a id="toc-How-can-I-concatenate-video-files_003f" href="#How-can-I-concatenate-video-files_003f">3.14 How can I concatenate video files?</a>
<ul class="no-bullet">
<li><a id="toc-Concatenating-using-the-concat-filter" href="#Concatenating-using-the-concat-filter">3.14.1 Concatenating using the concat <em>filter</em></a></li>
<li><a id="toc-Concatenating-using-the-concat-demuxer" href="#Concatenating-using-the-concat-demuxer">3.14.2 Concatenating using the concat <em>demuxer</em></a></li>
<li><a id="toc-Concatenating-using-the-concat-protocol-_0028file-level_0029" href="#Concatenating-using-the-concat-protocol-_0028file-level_0029">3.14.3 Concatenating using the concat <em>protocol</em> (file level)</a></li>
<li><a id="toc-Concatenating-using-raw-audio-and-video" href="#Concatenating-using-raw-audio-and-video">3.14.4 Concatenating using raw audio and video</a></li>
</ul></li>
<li><a id="toc-Using-_002df-lavfi_002c-audio-becomes-mono-for-no-apparent-reason_002e" href="#Using-_002df-lavfi_002c-audio-becomes-mono-for-no-apparent-reason_002e">3.15 Using <samp>-f lavfi</samp>, audio becomes mono for no apparent reason.</a></li>
<li><a id="toc-Why-does-FFmpeg-not-see-the-subtitles-in-my-VOB-file_003f" href="#Why-does-FFmpeg-not-see-the-subtitles-in-my-VOB-file_003f">3.16 Why does FFmpeg not see the subtitles in my VOB file?</a></li>
<li><a id="toc-Why-was-the-ffmpeg-_002dsameq-option-removed_003f-What-to-use-instead_003f" href="#Why-was-the-ffmpeg-_002dsameq-option-removed_003f-What-to-use-instead_003f">3.17 Why was the <code>ffmpeg</code> <samp>-sameq</samp> option removed? What to use instead?</a></li>
<li><a id="toc-I-have-a-stretched-video_002c-why-does-scaling-does-not-fix-it_003f" href="#I-have-a-stretched-video_002c-why-does-scaling-does-not-fix-it_003f">3.18 I have a stretched video, why does scaling does not fix it?</a></li>
<li><a id="toc-How-do-I-run-ffmpeg-as-a-background-task_003f" href="#How-do-I-run-ffmpeg-as-a-background-task_003f">3.19 How do I run ffmpeg as a background task?</a></li>
<li><a id="toc-How-do-I-prevent-ffmpeg-from-suspending-with-a-message-like-suspended-_0028tty-output_0029_003f" href="#How-do-I-prevent-ffmpeg-from-suspending-with-a-message-like-suspended-_0028tty-output_0029_003f">3.20 How do I prevent ffmpeg from suspending with a message like <em>suspended (tty output)</em>?</a></li>
</ul></li>
<li><a id="toc-Development" href="#Development">4 Development</a>
<ul class="no-bullet">
<li><a id="toc-Are-there-examples-illustrating-how-to-use-the-FFmpeg-libraries_002c-particularly-libavcodec-and-libavformat_003f" href="#Are-there-examples-illustrating-how-to-use-the-FFmpeg-libraries_002c-particularly-libavcodec-and-libavformat_003f">4.1 Are there examples illustrating how to use the FFmpeg libraries, particularly libavcodec and libavformat?</a></li>
<li><a id="toc-Can-you-support-my-C-compiler-XXX_003f" href="#Can-you-support-my-C-compiler-XXX_003f">4.2 Can you support my C compiler XXX?</a></li>
<li><a id="toc-Is-Microsoft-Visual-C_002b_002b-supported_003f" href="#Is-Microsoft-Visual-C_002b_002b-supported_003f">4.3 Is Microsoft Visual C++ supported?</a></li>
<li><a id="toc-Can-you-add-automake_002c-libtool-or-autoconf-support_003f" href="#Can-you-add-automake_002c-libtool-or-autoconf-support_003f">4.4 Can you add automake, libtool or autoconf support?</a></li>
<li><a id="toc-Why-not-rewrite-FFmpeg-in-object_002doriented-C_002b_002b_003f" href="#Why-not-rewrite-FFmpeg-in-object_002doriented-C_002b_002b_003f">4.5 Why not rewrite FFmpeg in object-oriented C++?</a></li>
<li><a id="toc-Why-are-the-ffmpeg-programs-devoid-of-debugging-symbols_003f" href="#Why-are-the-ffmpeg-programs-devoid-of-debugging-symbols_003f">4.6 Why are the ffmpeg programs devoid of debugging symbols?</a></li>
<li><a id="toc-I-do-not-like-the-LGPL_002c-can-I-contribute-code-under-the-GPL-instead_003f" href="#I-do-not-like-the-LGPL_002c-can-I-contribute-code-under-the-GPL-instead_003f">4.7 I do not like the LGPL, can I contribute code under the GPL instead?</a></li>
<li><a id="toc-I_0027m-using-FFmpeg-from-within-my-C-application-but-the-linker-complains-about-missing-symbols-from-the-libraries-themselves_002e" href="#I_0027m-using-FFmpeg-from-within-my-C-application-but-the-linker-complains-about-missing-symbols-from-the-libraries-themselves_002e">4.8 I&rsquo;m using FFmpeg from within my C application but the linker complains about missing symbols from the libraries themselves.</a></li>
<li><a id="toc-I_0027m-using-FFmpeg-from-within-my-C_002b_002b-application-but-the-linker-complains-about-missing-symbols-which-seem-to-be-available_002e" href="#I_0027m-using-FFmpeg-from-within-my-C_002b_002b-application-but-the-linker-complains-about-missing-symbols-which-seem-to-be-available_002e">4.9 I&rsquo;m using FFmpeg from within my C++ application but the linker complains about missing symbols which seem to be available.</a></li>
<li><a id="toc-I_0027m-using-libavutil-from-within-my-C_002b_002b-application-but-the-compiler-complains-about-_0027UINT64_005fC_0027-was-not-declared-in-this-scope" href="#I_0027m-using-libavutil-from-within-my-C_002b_002b-application-but-the-compiler-complains-about-_0027UINT64_005fC_0027-was-not-declared-in-this-scope">4.10 I&rsquo;m using libavutil from within my C++ application but the compiler complains about &rsquo;UINT64_C&rsquo; was not declared in this scope</a></li>
<li><a id="toc-I-have-a-file-in-memory-_002f-a-API-different-from-_002aopen_002f_002aread_002f-libc-how-do-I-use-it-with-libavformat_003f" href="#I-have-a-file-in-memory-_002f-a-API-different-from-_002aopen_002f_002aread_002f-libc-how-do-I-use-it-with-libavformat_003f">4.11 I have a file in memory / a API different from *open/*read/ libc how do I use it with libavformat?</a></li>
<li><a id="toc-Where-is-the-documentation-about-ffv1_002c-msmpeg4_002c-asv1_002c-4xm_003f" href="#Where-is-the-documentation-about-ffv1_002c-msmpeg4_002c-asv1_002c-4xm_003f">4.12 Where is the documentation about ffv1, msmpeg4, asv1, 4xm?</a></li>
<li><a id="toc-How-do-I-feed-H_002e263_002dRTP-_0028and-other-codecs-in-RTP_0029-to-libavcodec_003f" href="#How-do-I-feed-H_002e263_002dRTP-_0028and-other-codecs-in-RTP_0029-to-libavcodec_003f">4.13 How do I feed H.263-RTP (and other codecs in RTP) to libavcodec?</a></li>
<li><a id="toc-AVStream_002er_005fframe_005frate-is-wrong_002c-it-is-much-larger-than-the-frame-rate_002e" href="#AVStream_002er_005fframe_005frate-is-wrong_002c-it-is-much-larger-than-the-frame-rate_002e">4.14 AVStream.r_frame_rate is wrong, it is much larger than the frame rate.</a></li>
<li><a id="toc-Why-is-make-fate-not-running-all-tests_003f" href="#Why-is-make-fate-not-running-all-tests_003f">4.15 Why is <code>make fate</code> not running all tests?</a></li>
<li><a id="toc-Why-is-make-fate-not-finding-the-samples_003f" href="#Why-is-make-fate-not-finding-the-samples_003f">4.16 Why is <code>make fate</code> not finding the samples?</a></li>
</ul></li>
</ul>
</div>
</div>
<a name="General-Questions"></a>
<h2 class="chapter">1 General Questions<span class="pull-right"><a class="anchor hidden-xs" href="#General-Questions" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-General-Questions" aria-hidden="true">TOC</a></span></h2>
<a name="Why-doesn_0027t-FFmpeg-support-feature-_005bxyz_005d_003f"></a>
<h3 class="section">1.1 Why doesn&rsquo;t FFmpeg support feature [xyz]?<span class="pull-right"><a class="anchor hidden-xs" href="#Why-doesn_0027t-FFmpeg-support-feature-_005bxyz_005d_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Why-doesn_0027t-FFmpeg-support-feature-_005bxyz_005d_003f" aria-hidden="true">TOC</a></span></h3>
<p>Because no one has taken on that task yet. FFmpeg development is
driven by the tasks that are important to the individual developers.
If there is a feature that is important to you, the best way to get
it implemented is to undertake the task yourself or sponsor a developer.
</p>
<a name="FFmpeg-does-not-support-codec-XXX_002e-Can-you-include-a-Windows-DLL-loader-to-support-it_003f"></a>
<h3 class="section">1.2 FFmpeg does not support codec XXX. Can you include a Windows DLL loader to support it?<span class="pull-right"><a class="anchor hidden-xs" href="#FFmpeg-does-not-support-codec-XXX_002e-Can-you-include-a-Windows-DLL-loader-to-support-it_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-FFmpeg-does-not-support-codec-XXX_002e-Can-you-include-a-Windows-DLL-loader-to-support-it_003f" aria-hidden="true">TOC</a></span></h3>
<p>No. Windows DLLs are not portable, bloated and often slow.
Moreover FFmpeg strives to support all codecs natively.
A DLL loader is not conducive to that goal.
</p>
<a name="I-cannot-read-this-file-although-this-format-seems-to-be-supported-by-ffmpeg_002e"></a>
<h3 class="section">1.3 I cannot read this file although this format seems to be supported by ffmpeg.<span class="pull-right"><a class="anchor hidden-xs" href="#I-cannot-read-this-file-although-this-format-seems-to-be-supported-by-ffmpeg_002e" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-I-cannot-read-this-file-although-this-format-seems-to-be-supported-by-ffmpeg_002e" aria-hidden="true">TOC</a></span></h3>
<p>Even if ffmpeg can read the container format, it may not support all its
codecs. Please consult the supported codec list in the ffmpeg
documentation.
</p>
<a name="Which-codecs-are-supported-by-Windows_003f"></a>
<h3 class="section">1.4 Which codecs are supported by Windows?<span class="pull-right"><a class="anchor hidden-xs" href="#Which-codecs-are-supported-by-Windows_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Which-codecs-are-supported-by-Windows_003f" aria-hidden="true">TOC</a></span></h3>
<p>Windows does not support standard formats like MPEG very well, unless you
install some additional codecs.
</p>
<p>The following list of video codecs should work on most Windows systems:
</p><dl compact="compact">
<dt><span><samp>msmpeg4v2</samp></span></dt>
<dd><p>.avi/.asf
</p></dd>
<dt><span><samp>msmpeg4</samp></span></dt>
<dd><p>.asf only
</p></dd>
<dt><span><samp>wmv1</samp></span></dt>
<dd><p>.asf only
</p></dd>
<dt><span><samp>wmv2</samp></span></dt>
<dd><p>.asf only
</p></dd>
<dt><span><samp>mpeg4</samp></span></dt>
<dd><p>Only if you have some MPEG-4 codec like ffdshow or Xvid installed.
</p></dd>
<dt><span><samp>mpeg1video</samp></span></dt>
<dd><p>.mpg only
</p></dd>
</dl>
<p>Note, ASF files often have .wmv or .wma extensions in Windows. It should also
be mentioned that Microsoft claims a patent on the ASF format, and may sue
or threaten users who create ASF files with non-Microsoft software. It is
strongly advised to avoid ASF where possible.
</p>
<p>The following list of audio codecs should work on most Windows systems:
</p><dl compact="compact">
<dt><span><samp>adpcm_ima_wav</samp></span></dt>
<dt><span><samp>adpcm_ms</samp></span></dt>
<dt><span><samp>pcm_s16le</samp></span></dt>
<dd><p>always
</p></dd>
<dt><span><samp>libmp3lame</samp></span></dt>
<dd><p>If some MP3 codec like LAME is installed.
</p></dd>
</dl>
<a name="Compilation"></a>
<h2 class="chapter">2 Compilation<span class="pull-right"><a class="anchor hidden-xs" href="#Compilation" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Compilation" aria-hidden="true">TOC</a></span></h2>
<a name="error_003a-can_0027t-find-a-register-in-class-_0027GENERAL_005fREGS_0027-while-reloading-_0027asm_0027"></a>
<h3 class="section">2.1 <code>error: can't find a register in class 'GENERAL_REGS' while reloading 'asm'</code><span class="pull-right"><a class="anchor hidden-xs" href="#error_003a-can_0027t-find-a-register-in-class-_0027GENERAL_005fREGS_0027-while-reloading-_0027asm_0027" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-error_003a-can_0027t-find-a-register-in-class-_0027GENERAL_005fREGS_0027-while-reloading-_0027asm_0027" aria-hidden="true">TOC</a></span></h3>
<p>This is a bug in gcc. Do not report it to us. Instead, please report it to
the gcc developers. Note that we will not add workarounds for gcc bugs.
</p>
<p>Also note that (some of) the gcc developers believe this is not a bug or
not a bug they should fix:
<a href="https://gcc.gnu.org/bugzilla/show_bug.cgi?id=11203">https://gcc.gnu.org/bugzilla/show_bug.cgi?id=11203</a>.
Then again, some of them do not know the difference between an undecidable
problem and an NP-hard problem...
</p>
<a name="I-have-installed-this-library-with-my-distro_0027s-package-manager_002e-Why-does-configure-not-see-it_003f"></a>
<h3 class="section">2.2 I have installed this library with my distro&rsquo;s package manager. Why does <code>configure</code> not see it?<span class="pull-right"><a class="anchor hidden-xs" href="#I-have-installed-this-library-with-my-distro_0027s-package-manager_002e-Why-does-configure-not-see-it_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-I-have-installed-this-library-with-my-distro_0027s-package-manager_002e-Why-does-configure-not-see-it_003f" aria-hidden="true">TOC</a></span></h3>
<p>Distributions usually split libraries in several packages. The main package
contains the files necessary to run programs using the library. The
development package contains the files necessary to build programs using the
library. Sometimes, docs and/or data are in a separate package too.
</p>
<p>To build FFmpeg, you need to install the development package. It is usually
called <samp>libfoo-dev</samp> or <samp>libfoo-devel</samp>. You can remove it after the
build is finished, but be sure to keep the main package.
</p>
<a name="How-do-I-make-pkg_002dconfig-find-my-libraries_003f"></a>
<h3 class="section">2.3 How do I make <code>pkg-config</code> find my libraries?<span class="pull-right"><a class="anchor hidden-xs" href="#How-do-I-make-pkg_002dconfig-find-my-libraries_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-How-do-I-make-pkg_002dconfig-find-my-libraries_003f" aria-hidden="true">TOC</a></span></h3>
<p>Somewhere along with your libraries, there is a <samp>.pc</samp> file (or several)
in a <samp>pkgconfig</samp> directory. You need to set environment variables to
point <code>pkg-config</code> to these files.
</p>
<p>If you need to <em>add</em> directories to <code>pkg-config</code>&rsquo;s search list
(typical use case: library installed separately), add it to
<code>$PKG_CONFIG_PATH</code>:
</p>
<div class="example">
<pre class="example">export PKG_CONFIG_PATH=/opt/x264/lib/pkgconfig:/opt/opus/lib/pkgconfig
</pre></div>
<p>If you need to <em>replace</em> <code>pkg-config</code>&rsquo;s search list
(typical use case: cross-compiling), set it in
<code>$PKG_CONFIG_LIBDIR</code>:
</p>
<div class="example">
<pre class="example">export PKG_CONFIG_LIBDIR=/home/me/cross/usr/lib/pkgconfig:/home/me/cross/usr/local/lib/pkgconfig
</pre></div>
<p>If you need to know the library&rsquo;s internal dependencies (typical use: static
linking), add the <code>--static</code> option to <code>pkg-config</code>:
</p>
<div class="example">
<pre class="example">./configure --pkg-config-flags=--static
</pre></div>
<a name="How-do-I-use-pkg_002dconfig-when-cross_002dcompiling_003f"></a>
<h3 class="section">2.4 How do I use <code>pkg-config</code> when cross-compiling?<span class="pull-right"><a class="anchor hidden-xs" href="#How-do-I-use-pkg_002dconfig-when-cross_002dcompiling_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-How-do-I-use-pkg_002dconfig-when-cross_002dcompiling_003f" aria-hidden="true">TOC</a></span></h3>
<p>The best way is to install <code>pkg-config</code> in your cross-compilation
environment. It will automatically use the cross-compilation libraries.
</p>
<p>You can also use <code>pkg-config</code> from the host environment by
specifying explicitly <code>--pkg-config=pkg-config</code> to <code>configure</code>.
In that case, you must point <code>pkg-config</code> to the correct directories
using the <code>PKG_CONFIG_LIBDIR</code>, as explained in the previous entry.
</p>
<p>As an intermediate solution, you can place in your cross-compilation
environment a script that calls the host <code>pkg-config</code> with
<code>PKG_CONFIG_LIBDIR</code> set. That script can look like that:
</p>
<div class="example">
<pre class="example">#!/bin/sh
PKG_CONFIG_LIBDIR=/path/to/cross/lib/pkgconfig
export PKG_CONFIG_LIBDIR
exec /usr/bin/pkg-config &quot;$@&quot;
</pre></div>
<a name="Usage"></a>
<h2 class="chapter">3 Usage<span class="pull-right"><a class="anchor hidden-xs" href="#Usage" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Usage" aria-hidden="true">TOC</a></span></h2>
<a name="ffmpeg-does-not-work_003b-what-is-wrong_003f"></a>
<h3 class="section">3.1 ffmpeg does not work; what is wrong?<span class="pull-right"><a class="anchor hidden-xs" href="#ffmpeg-does-not-work_003b-what-is-wrong_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-ffmpeg-does-not-work_003b-what-is-wrong_003f" aria-hidden="true">TOC</a></span></h3>
<p>Try a <code>make distclean</code> in the ffmpeg source directory before the build.
If this does not help see
(<a href="https://ffmpeg.org/bugreports.html">https://ffmpeg.org/bugreports.html</a>).
</p>
<a name="How-do-I-encode-single-pictures-into-movies_003f"></a>
<h3 class="section">3.2 How do I encode single pictures into movies?<span class="pull-right"><a class="anchor hidden-xs" href="#How-do-I-encode-single-pictures-into-movies_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-How-do-I-encode-single-pictures-into-movies_003f" aria-hidden="true">TOC</a></span></h3>
<p>First, rename your pictures to follow a numerical sequence.
For example, img1.jpg, img2.jpg, img3.jpg,...
Then you may run:
</p>
<div class="example">
<pre class="example">ffmpeg -f image2 -i img%d.jpg /tmp/a.mpg
</pre></div>
<p>Notice that &lsquo;<samp>%d</samp>&rsquo; is replaced by the image number.
</p>
<p><samp>img%03d.jpg</samp> means the sequence <samp>img001.jpg</samp>, <samp>img002.jpg</samp>, etc.
</p>
<p>Use the <samp>-start_number</samp> option to declare a starting number for
the sequence. This is useful if your sequence does not start with
<samp>img001.jpg</samp> but is still in a numerical order. The following
example will start with <samp>img100.jpg</samp>:
</p>
<div class="example">
<pre class="example">ffmpeg -f image2 -start_number 100 -i img%d.jpg /tmp/a.mpg
</pre></div>
<p>If you have large number of pictures to rename, you can use the
following command to ease the burden. The command, using the bourne
shell syntax, symbolically links all files in the current directory
that match <code>*jpg</code> to the <samp>/tmp</samp> directory in the sequence of
<samp>img001.jpg</samp>, <samp>img002.jpg</samp> and so on.
</p>
<div class="example">
<pre class="example">x=1; for i in *jpg; do counter=$(printf %03d $x); ln -s &quot;$i&quot; /tmp/img&quot;$counter&quot;.jpg; x=$(($x+1)); done
</pre></div>
<p>If you want to sequence them by oldest modified first, substitute
<code>$(ls -r -t *jpg)</code> in place of <code>*jpg</code>.
</p>
<p>Then run:
</p>
<div class="example">
<pre class="example">ffmpeg -f image2 -i /tmp/img%03d.jpg /tmp/a.mpg
</pre></div>
<p>The same logic is used for any image format that ffmpeg reads.
</p>
<p>You can also use <code>cat</code> to pipe images to ffmpeg:
</p>
<div class="example">
<pre class="example">cat *.jpg | ffmpeg -f image2pipe -c:v mjpeg -i - output.mpg
</pre></div>
<a name="How-do-I-encode-movie-to-single-pictures_003f"></a>
<h3 class="section">3.3 How do I encode movie to single pictures?<span class="pull-right"><a class="anchor hidden-xs" href="#How-do-I-encode-movie-to-single-pictures_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-How-do-I-encode-movie-to-single-pictures_003f" aria-hidden="true">TOC</a></span></h3>
<p>Use:
</p>
<div class="example">
<pre class="example">ffmpeg -i movie.mpg movie%d.jpg
</pre></div>
<p>The <samp>movie.mpg</samp> used as input will be converted to
<samp>movie1.jpg</samp>, <samp>movie2.jpg</samp>, etc...
</p>
<p>Instead of relying on file format self-recognition, you may also use
</p><dl compact="compact">
<dt><span><samp>-c:v ppm</samp></span></dt>
<dt><span><samp>-c:v png</samp></span></dt>
<dt><span><samp>-c:v mjpeg</samp></span></dt>
</dl>
<p>to force the encoding.
</p>
<p>Applying that to the previous example:
</p><div class="example">
<pre class="example">ffmpeg -i movie.mpg -f image2 -c:v mjpeg menu%d.jpg
</pre></div>
<p>Beware that there is no &quot;jpeg&quot; codec. Use &quot;mjpeg&quot; instead.
</p>
<a name="Why-do-I-see-a-slight-quality-degradation-with-multithreaded-MPEG_002a-encoding_003f"></a>
<h3 class="section">3.4 Why do I see a slight quality degradation with multithreaded MPEG* encoding?<span class="pull-right"><a class="anchor hidden-xs" href="#Why-do-I-see-a-slight-quality-degradation-with-multithreaded-MPEG_002a-encoding_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Why-do-I-see-a-slight-quality-degradation-with-multithreaded-MPEG_002a-encoding_003f" aria-hidden="true">TOC</a></span></h3>
<p>For multithreaded MPEG* encoding, the encoded slices must be independent,
otherwise thread n would practically have to wait for n-1 to finish, so it&rsquo;s
quite logical that there is a small reduction of quality. This is not a bug.
</p>
<a name="How-can-I-read-from-the-standard-input-or-write-to-the-standard-output_003f"></a>
<h3 class="section">3.5 How can I read from the standard input or write to the standard output?<span class="pull-right"><a class="anchor hidden-xs" href="#How-can-I-read-from-the-standard-input-or-write-to-the-standard-output_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-How-can-I-read-from-the-standard-input-or-write-to-the-standard-output_003f" aria-hidden="true">TOC</a></span></h3>
<p>Use <samp>-</samp> as file name.
</p>
<a name="g_t_002df-jpeg-doesn_0027t-work_002e"></a>
<h3 class="section">3.6 -f jpeg doesn&rsquo;t work.<span class="pull-right"><a class="anchor hidden-xs" href="#_002df-jpeg-doesn_0027t-work_002e" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-_002df-jpeg-doesn_0027t-work_002e" aria-hidden="true">TOC</a></span></h3>
<p>Try &rsquo;-f image2 test%d.jpg&rsquo;.
</p>
<a name="Why-can-I-not-change-the-frame-rate_003f"></a>
<h3 class="section">3.7 Why can I not change the frame rate?<span class="pull-right"><a class="anchor hidden-xs" href="#Why-can-I-not-change-the-frame-rate_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Why-can-I-not-change-the-frame-rate_003f" aria-hidden="true">TOC</a></span></h3>
<p>Some codecs, like MPEG-1/2, only allow a small number of fixed frame rates.
Choose a different codec with the -c:v command line option.
</p>
<a name="How-do-I-encode-Xvid-or-DivX-video-with-ffmpeg_003f"></a>
<h3 class="section">3.8 How do I encode Xvid or DivX video with ffmpeg?<span class="pull-right"><a class="anchor hidden-xs" href="#How-do-I-encode-Xvid-or-DivX-video-with-ffmpeg_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-How-do-I-encode-Xvid-or-DivX-video-with-ffmpeg_003f" aria-hidden="true">TOC</a></span></h3>
<p>Both Xvid and DivX (version 4+) are implementations of the ISO MPEG-4
standard (note that there are many other coding formats that use this
same standard). Thus, use &rsquo;-c:v mpeg4&rsquo; to encode in these formats. The
default fourcc stored in an MPEG-4-coded file will be &rsquo;FMP4&rsquo;. If you want
a different fourcc, use the &rsquo;-vtag&rsquo; option. E.g., &rsquo;-vtag xvid&rsquo; will
force the fourcc &rsquo;xvid&rsquo; to be stored as the video fourcc rather than the
default.
</p>
<a name="Which-are-good-parameters-for-encoding-high-quality-MPEG_002d4_003f"></a>
<h3 class="section">3.9 Which are good parameters for encoding high quality MPEG-4?<span class="pull-right"><a class="anchor hidden-xs" href="#Which-are-good-parameters-for-encoding-high-quality-MPEG_002d4_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Which-are-good-parameters-for-encoding-high-quality-MPEG_002d4_003f" aria-hidden="true">TOC</a></span></h3>
<p>&rsquo;-mbd rd -flags +mv4+aic -trellis 2 -cmp 2 -subcmp 2 -g 300 -pass 1/2&rsquo;,
things to try: &rsquo;-bf 2&rsquo;, &rsquo;-mpv_flags qp_rd&rsquo;, &rsquo;-mpv_flags mv0&rsquo;, &rsquo;-mpv_flags skip_rd&rsquo;.
</p>
<a name="Which-are-good-parameters-for-encoding-high-quality-MPEG_002d1_002fMPEG_002d2_003f"></a>
<h3 class="section">3.10 Which are good parameters for encoding high quality MPEG-1/MPEG-2?<span class="pull-right"><a class="anchor hidden-xs" href="#Which-are-good-parameters-for-encoding-high-quality-MPEG_002d1_002fMPEG_002d2_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Which-are-good-parameters-for-encoding-high-quality-MPEG_002d1_002fMPEG_002d2_003f" aria-hidden="true">TOC</a></span></h3>
<p>&rsquo;-mbd rd -trellis 2 -cmp 2 -subcmp 2 -g 100 -pass 1/2&rsquo;
but beware the &rsquo;-g 100&rsquo; might cause problems with some decoders.
Things to try: &rsquo;-bf 2&rsquo;, &rsquo;-mpv_flags qp_rd&rsquo;, &rsquo;-mpv_flags mv0&rsquo;, &rsquo;-mpv_flags skip_rd&rsquo;.
</p>
<a name="Interlaced-video-looks-very-bad-when-encoded-with-ffmpeg_002c-what-is-wrong_003f"></a>
<h3 class="section">3.11 Interlaced video looks very bad when encoded with ffmpeg, what is wrong?<span class="pull-right"><a class="anchor hidden-xs" href="#Interlaced-video-looks-very-bad-when-encoded-with-ffmpeg_002c-what-is-wrong_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Interlaced-video-looks-very-bad-when-encoded-with-ffmpeg_002c-what-is-wrong_003f" aria-hidden="true">TOC</a></span></h3>
<p>You should use &rsquo;-flags +ilme+ildct&rsquo; and maybe &rsquo;-flags +alt&rsquo; for interlaced
material, and try &rsquo;-top 0/1&rsquo; if the result looks really messed-up.
</p>
<a name="How-can-I-read-DirectShow-files_003f"></a>
<h3 class="section">3.12 How can I read DirectShow files?<span class="pull-right"><a class="anchor hidden-xs" href="#How-can-I-read-DirectShow-files_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-How-can-I-read-DirectShow-files_003f" aria-hidden="true">TOC</a></span></h3>
<p>If you have built FFmpeg with <code>./configure --enable-avisynth</code>
(only possible on MinGW/Cygwin platforms),
then you may use any file that DirectShow can read as input.
</p>
<p>Just create an &quot;input.avs&quot; text file with this single line ...
</p><div class="example">
<pre class="example">DirectShowSource(&quot;C:\path to your file\yourfile.asf&quot;)
</pre></div>
<p>... and then feed that text file to ffmpeg:
</p><div class="example">
<pre class="example">ffmpeg -i input.avs
</pre></div>
<p>For ANY other help on AviSynth, please visit the
<a href="http://www.avisynth.org/">AviSynth homepage</a>.
</p>
<a name="How-can-I-join-video-files_003f"></a>
<h3 class="section">3.13 How can I join video files?<span class="pull-right"><a class="anchor hidden-xs" href="#How-can-I-join-video-files_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-How-can-I-join-video-files_003f" aria-hidden="true">TOC</a></span></h3>
<p>To &quot;join&quot; video files is quite ambiguous. The following list explains the
different kinds of &quot;joining&quot; and points out how those are addressed in
FFmpeg. To join video files may mean:
</p>
<ul>
<li> To put them one after the other: this is called to <em>concatenate</em> them
(in short: concat) and is addressed
<a href="#How-can-I-concatenate-video-files">in this very faq</a>.
</li><li> To put them together in the same file, to let the user choose between the
different versions (example: different audio languages): this is called to
<em>multiplex</em> them together (in short: mux), and is done by simply
invoking ffmpeg with several <samp>-i</samp> options.
</li><li> For audio, to put all channels together in a single stream (example: two
mono streams into one stereo stream): this is sometimes called to
<em>merge</em> them, and can be done using the
<a href="ffmpeg-filters.html#amerge"><code>amerge</code></a> filter.
</li><li> For audio, to play one on top of the other: this is called to <em>mix</em>
them, and can be done by first merging them into a single stream and then
using the <a href="ffmpeg-filters.html#pan"><code>pan</code></a> filter to mix
the channels at will.
</li><li> For video, to display both together, side by side or one on top of a part of
the other; it can be done using the
<a href="ffmpeg-filters.html#overlay"><code>overlay</code></a> video filter.
</li></ul>
<span id="How-can-I-concatenate-video-files"></span><a name="How-can-I-concatenate-video-files_003f"></a>
<h3 class="section">3.14 How can I concatenate video files?<span class="pull-right"><a class="anchor hidden-xs" href="#How-can-I-concatenate-video-files_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-How-can-I-concatenate-video-files_003f" aria-hidden="true">TOC</a></span></h3>
<p>There are several solutions, depending on the exact circumstances.
</p>
<a name="Concatenating-using-the-concat-filter"></a>
<h4 class="subsection">3.14.1 Concatenating using the concat <em>filter</em><span class="pull-right"><a class="anchor hidden-xs" href="#Concatenating-using-the-concat-filter" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Concatenating-using-the-concat-filter" aria-hidden="true">TOC</a></span></h4>
<p>FFmpeg has a <a href="ffmpeg-filters.html#concat"><code>concat</code></a> filter designed specifically for that, with examples in the
documentation. This operation is recommended if you need to re-encode.
</p>
<a name="Concatenating-using-the-concat-demuxer"></a>
<h4 class="subsection">3.14.2 Concatenating using the concat <em>demuxer</em><span class="pull-right"><a class="anchor hidden-xs" href="#Concatenating-using-the-concat-demuxer" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Concatenating-using-the-concat-demuxer" aria-hidden="true">TOC</a></span></h4>
<p>FFmpeg has a <a href="ffmpeg-formats.html#concat"><code>concat</code></a> demuxer which you can use when you want to avoid a re-encode and
your format doesn&rsquo;t support file level concatenation.
</p>
<a name="Concatenating-using-the-concat-protocol-_0028file-level_0029"></a>
<h4 class="subsection">3.14.3 Concatenating using the concat <em>protocol</em> (file level)<span class="pull-right"><a class="anchor hidden-xs" href="#Concatenating-using-the-concat-protocol-_0028file-level_0029" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Concatenating-using-the-concat-protocol-_0028file-level_0029" aria-hidden="true">TOC</a></span></h4>
<p>FFmpeg has a <a href="ffmpeg-protocols.html#concat"><code>concat</code></a> protocol designed specifically for that, with examples in the
documentation.
</p>
<p>A few multimedia containers (MPEG-1, MPEG-2 PS, DV) allow one to concatenate
video by merely concatenating the files containing them.
</p>
<p>Hence you may concatenate your multimedia files by first transcoding them to
these privileged formats, then using the humble <code>cat</code> command (or the
equally humble <code>copy</code> under Windows), and finally transcoding back to your
format of choice.
</p>
<div class="example">
<pre class="example">ffmpeg -i input1.avi -qscale:v 1 intermediate1.mpg
ffmpeg -i input2.avi -qscale:v 1 intermediate2.mpg
cat intermediate1.mpg intermediate2.mpg &gt; intermediate_all.mpg
ffmpeg -i intermediate_all.mpg -qscale:v 2 output.avi
</pre></div>
<p>Additionally, you can use the <code>concat</code> protocol instead of <code>cat</code> or
<code>copy</code> which will avoid creation of a potentially huge intermediate file.
</p>
<div class="example">
<pre class="example">ffmpeg -i input1.avi -qscale:v 1 intermediate1.mpg
ffmpeg -i input2.avi -qscale:v 1 intermediate2.mpg
ffmpeg -i concat:&quot;intermediate1.mpg|intermediate2.mpg&quot; -c copy intermediate_all.mpg
ffmpeg -i intermediate_all.mpg -qscale:v 2 output.avi
</pre></div>
<p>Note that you may need to escape the character &quot;|&quot; which is special for many
shells.
</p>
<p>Another option is usage of named pipes, should your platform support it:
</p>
<div class="example">
<pre class="example">mkfifo intermediate1.mpg
mkfifo intermediate2.mpg
ffmpeg -i input1.avi -qscale:v 1 -y intermediate1.mpg &lt; /dev/null &amp;
ffmpeg -i input2.avi -qscale:v 1 -y intermediate2.mpg &lt; /dev/null &amp;
cat intermediate1.mpg intermediate2.mpg |\
ffmpeg -f mpeg -i - -c:v mpeg4 -c:a libmp3lame output.avi
</pre></div>
<a name="Concatenating-using-raw-audio-and-video"></a>
<h4 class="subsection">3.14.4 Concatenating using raw audio and video<span class="pull-right"><a class="anchor hidden-xs" href="#Concatenating-using-raw-audio-and-video" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Concatenating-using-raw-audio-and-video" aria-hidden="true">TOC</a></span></h4>
<p>Similarly, the yuv4mpegpipe format, and the raw video, raw audio codecs also
allow concatenation, and the transcoding step is almost lossless.
When using multiple yuv4mpegpipe(s), the first line needs to be discarded
from all but the first stream. This can be accomplished by piping through
<code>tail</code> as seen below. Note that when piping through <code>tail</code> you
must use command grouping, <code>{ ;}</code>, to background properly.
</p>
<p>For example, let&rsquo;s say we want to concatenate two FLV files into an
output.flv file:
</p>
<div class="example">
<pre class="example">mkfifo temp1.a
mkfifo temp1.v
mkfifo temp2.a
mkfifo temp2.v
mkfifo all.a
mkfifo all.v
ffmpeg -i input1.flv -vn -f u16le -c:a pcm_s16le -ac 2 -ar 44100 - &gt; temp1.a &lt; /dev/null &amp;
ffmpeg -i input2.flv -vn -f u16le -c:a pcm_s16le -ac 2 -ar 44100 - &gt; temp2.a &lt; /dev/null &amp;
ffmpeg -i input1.flv -an -f yuv4mpegpipe - &gt; temp1.v &lt; /dev/null &amp;
{ ffmpeg -i input2.flv -an -f yuv4mpegpipe - &lt; /dev/null | tail -n +2 &gt; temp2.v ; } &amp;
cat temp1.a temp2.a &gt; all.a &amp;
cat temp1.v temp2.v &gt; all.v &amp;
ffmpeg -f u16le -c:a pcm_s16le -ac 2 -ar 44100 -i all.a \
-f yuv4mpegpipe -i all.v \
-y output.flv
rm temp[12].[av] all.[av]
</pre></div>
<a name="Using-_002df-lavfi_002c-audio-becomes-mono-for-no-apparent-reason_002e"></a>
<h3 class="section">3.15 Using <samp>-f lavfi</samp>, audio becomes mono for no apparent reason.<span class="pull-right"><a class="anchor hidden-xs" href="#Using-_002df-lavfi_002c-audio-becomes-mono-for-no-apparent-reason_002e" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Using-_002df-lavfi_002c-audio-becomes-mono-for-no-apparent-reason_002e" aria-hidden="true">TOC</a></span></h3>
<p>Use <samp>-dumpgraph -</samp> to find out exactly where the channel layout is
lost.
</p>
<p>Most likely, it is through <code>auto-inserted aresample</code>. Try to understand
why the converting filter was needed at that place.
</p>
<p>Just before the output is a likely place, as <samp>-f lavfi</samp> currently
only support packed S16.
</p>
<p>Then insert the correct <code>aformat</code> explicitly in the filtergraph,
specifying the exact format.
</p>
<div class="example">
<pre class="example">aformat=sample_fmts=s16:channel_layouts=stereo
</pre></div>
<a name="Why-does-FFmpeg-not-see-the-subtitles-in-my-VOB-file_003f"></a>
<h3 class="section">3.16 Why does FFmpeg not see the subtitles in my VOB file?<span class="pull-right"><a class="anchor hidden-xs" href="#Why-does-FFmpeg-not-see-the-subtitles-in-my-VOB-file_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Why-does-FFmpeg-not-see-the-subtitles-in-my-VOB-file_003f" aria-hidden="true">TOC</a></span></h3>
<p>VOB and a few other formats do not have a global header that describes
everything present in the file. Instead, applications are supposed to scan
the file to see what it contains. Since VOB files are frequently large, only
the beginning is scanned. If the subtitles happen only later in the file,
they will not be initially detected.
</p>
<p>Some applications, including the <code>ffmpeg</code> command-line tool, can only
work with streams that were detected during the initial scan; streams that
are detected later are ignored.
</p>
<p>The size of the initial scan is controlled by two options: <code>probesize</code>
(default ~5 Mo) and <code>analyzeduration</code> (default 5,000,000 µs = 5 s). For
the subtitle stream to be detected, both values must be large enough.
</p>
<a name="Why-was-the-ffmpeg-_002dsameq-option-removed_003f-What-to-use-instead_003f"></a>
<h3 class="section">3.17 Why was the <code>ffmpeg</code> <samp>-sameq</samp> option removed? What to use instead?<span class="pull-right"><a class="anchor hidden-xs" href="#Why-was-the-ffmpeg-_002dsameq-option-removed_003f-What-to-use-instead_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Why-was-the-ffmpeg-_002dsameq-option-removed_003f-What-to-use-instead_003f" aria-hidden="true">TOC</a></span></h3>
<p>The <samp>-sameq</samp> option meant &quot;same quantizer&quot;, and made sense only in a
very limited set of cases. Unfortunately, a lot of people mistook it for
&quot;same quality&quot; and used it in places where it did not make sense: it had
roughly the expected visible effect, but achieved it in a very inefficient
way.
</p>
<p>Each encoder has its own set of options to set the quality-vs-size balance,
use the options for the encoder you are using to set the quality level to a
point acceptable for your tastes. The most common options to do that are
<samp>-qscale</samp> and <samp>-qmax</samp>, but you should peruse the documentation
of the encoder you chose.
</p>
<a name="I-have-a-stretched-video_002c-why-does-scaling-does-not-fix-it_003f"></a>
<h3 class="section">3.18 I have a stretched video, why does scaling does not fix it?<span class="pull-right"><a class="anchor hidden-xs" href="#I-have-a-stretched-video_002c-why-does-scaling-does-not-fix-it_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-I-have-a-stretched-video_002c-why-does-scaling-does-not-fix-it_003f" aria-hidden="true">TOC</a></span></h3>
<p>A lot of video codecs and formats can store the <em>aspect ratio</em> of the
video: this is the ratio between the width and the height of either the full
image (DAR, display aspect ratio) or individual pixels (SAR, sample aspect
ratio). For example, EGA screens at resolution 640×350 had 4:3 DAR and 35:48
SAR.
</p>
<p>Most still image processing work with square pixels, i.e. 1:1 SAR, but a lot
of video standards, especially from the analogic-numeric transition era, use
non-square pixels.
</p>
<p>Most processing filters in FFmpeg handle the aspect ratio to avoid
stretching the image: cropping adjusts the DAR to keep the SAR constant,
scaling adjusts the SAR to keep the DAR constant.
</p>
<p>If you want to stretch, or “unstretch”, the image, you need to override the
information with the
<a href="ffmpeg-filters.html#setdar_002c-setsar"><code>setdar or setsar filters</code></a>.
</p>
<p>Do not forget to examine carefully the original video to check whether the
stretching comes from the image or from the aspect ratio information.
</p>
<p>For example, to fix a badly encoded EGA capture, use the following commands,
either the first one to upscale to square pixels or the second one to set
the correct aspect ratio or the third one to avoid transcoding (may not work
depending on the format / codec / player / phase of the moon):
</p>
<div class="example">
<pre class="example">ffmpeg -i ega_screen.nut -vf scale=640:480,setsar=1 ega_screen_scaled.nut
ffmpeg -i ega_screen.nut -vf setdar=4/3 ega_screen_anamorphic.nut
ffmpeg -i ega_screen.nut -aspect 4/3 -c copy ega_screen_overridden.nut
</pre></div>
<span id="background-task"></span><a name="How-do-I-run-ffmpeg-as-a-background-task_003f"></a>
<h3 class="section">3.19 How do I run ffmpeg as a background task?<span class="pull-right"><a class="anchor hidden-xs" href="#How-do-I-run-ffmpeg-as-a-background-task_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-How-do-I-run-ffmpeg-as-a-background-task_003f" aria-hidden="true">TOC</a></span></h3>
<p>ffmpeg normally checks the console input, for entries like &quot;q&quot; to stop
and &quot;?&quot; to give help, while performing operations. ffmpeg does not have a way of
detecting when it is running as a background task.
When it checks the console input, that can cause the process running ffmpeg
in the background to suspend.
</p>
<p>To prevent those input checks, allowing ffmpeg to run as a background task,
use the <a href="ffmpeg.html#stdin-option"><code>-nostdin</code> option</a>
in the ffmpeg invocation. This is effective whether you run ffmpeg in a shell
or invoke ffmpeg in its own process via an operating system API.
</p>
<p>As an alternative, when you are running ffmpeg in a shell, you can redirect
standard input to <code>/dev/null</code> (on Linux and macOS)
or <code>NUL</code> (on Windows). You can do this redirect either
on the ffmpeg invocation, or from a shell script which calls ffmpeg.
</p>
<p>For example:
</p>
<div class="example">
<pre class="example">ffmpeg -nostdin -i INPUT OUTPUT
</pre></div>
<p>or (on Linux, macOS, and other UNIX-like shells):
</p>
<div class="example">
<pre class="example">ffmpeg -i INPUT OUTPUT &lt;/dev/null
</pre></div>
<p>or (on Windows):
</p>
<div class="example">
<pre class="example">ffmpeg -i INPUT OUTPUT &lt;NUL
</pre></div>
<a name="How-do-I-prevent-ffmpeg-from-suspending-with-a-message-like-suspended-_0028tty-output_0029_003f"></a>
<h3 class="section">3.20 How do I prevent ffmpeg from suspending with a message like <em>suspended (tty output)</em>?<span class="pull-right"><a class="anchor hidden-xs" href="#How-do-I-prevent-ffmpeg-from-suspending-with-a-message-like-suspended-_0028tty-output_0029_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-How-do-I-prevent-ffmpeg-from-suspending-with-a-message-like-suspended-_0028tty-output_0029_003f" aria-hidden="true">TOC</a></span></h3>
<p>If you run ffmpeg in the background, you may find that its process suspends.
There may be a message like <em>suspended (tty output)</em>. The question is how
to prevent the process from being suspended.
</p>
<p>For example:
</p>
<div class="example">
<pre class="example">% ffmpeg -i INPUT OUTPUT &amp;&gt; ~/tmp/log.txt &amp;
[1] 93352
%
[1] + suspended (tty output) ffmpeg -i INPUT OUTPUT &amp;&gt;
</pre></div>
<p>The message &quot;tty output&quot; notwithstanding, the problem here is that
ffmpeg normally checks the console input when it runs. The operating system
detects this, and suspends the process until you can bring it to the
foreground and attend to it.
</p>
<p>The solution is to use the right techniques to tell ffmpeg not to consult
console input. You can use the
<a href="ffmpeg.html#stdin-option"><code>-nostdin</code> option</a>,
or redirect standard input with <code>&lt; /dev/null</code>.
See FAQ
<a href="#background-task"><em>How do I run ffmpeg as a background task?</em></a>
for details.
</p>
<a name="Development"></a>
<h2 class="chapter">4 Development<span class="pull-right"><a class="anchor hidden-xs" href="#Development" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Development" aria-hidden="true">TOC</a></span></h2>
<a name="Are-there-examples-illustrating-how-to-use-the-FFmpeg-libraries_002c-particularly-libavcodec-and-libavformat_003f"></a>
<h3 class="section">4.1 Are there examples illustrating how to use the FFmpeg libraries, particularly libavcodec and libavformat?<span class="pull-right"><a class="anchor hidden-xs" href="#Are-there-examples-illustrating-how-to-use-the-FFmpeg-libraries_002c-particularly-libavcodec-and-libavformat_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Are-there-examples-illustrating-how-to-use-the-FFmpeg-libraries_002c-particularly-libavcodec-and-libavformat_003f" aria-hidden="true">TOC</a></span></h3>
<p>Yes. Check the <samp>doc/examples</samp> directory in the source
repository, also available online at:
<a href="https://github.com/FFmpeg/FFmpeg/tree/master/doc/examples">https://github.com/FFmpeg/FFmpeg/tree/master/doc/examples</a>.
</p>
<p>Examples are also installed by default, usually in
<code>$PREFIX/share/ffmpeg/examples</code>.
</p>
<p>Also you may read the Developers Guide of the FFmpeg documentation. Alternatively,
examine the source code for one of the many open source projects that
already incorporate FFmpeg at (<a href="projects.html">projects.html</a>).
</p>
<a name="Can-you-support-my-C-compiler-XXX_003f"></a>
<h3 class="section">4.2 Can you support my C compiler XXX?<span class="pull-right"><a class="anchor hidden-xs" href="#Can-you-support-my-C-compiler-XXX_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Can-you-support-my-C-compiler-XXX_003f" aria-hidden="true">TOC</a></span></h3>
<p>It depends. If your compiler is C99-compliant, then patches to support
it are likely to be welcome if they do not pollute the source code
with <code>#ifdef</code>s related to the compiler.
</p>
<a name="Is-Microsoft-Visual-C_002b_002b-supported_003f"></a>
<h3 class="section">4.3 Is Microsoft Visual C++ supported?<span class="pull-right"><a class="anchor hidden-xs" href="#Is-Microsoft-Visual-C_002b_002b-supported_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Is-Microsoft-Visual-C_002b_002b-supported_003f" aria-hidden="true">TOC</a></span></h3>
<p>Yes. Please see the <a href="platform.html">Microsoft Visual C++</a>
section in the FFmpeg documentation.
</p>
<a name="Can-you-add-automake_002c-libtool-or-autoconf-support_003f"></a>
<h3 class="section">4.4 Can you add automake, libtool or autoconf support?<span class="pull-right"><a class="anchor hidden-xs" href="#Can-you-add-automake_002c-libtool-or-autoconf-support_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Can-you-add-automake_002c-libtool-or-autoconf-support_003f" aria-hidden="true">TOC</a></span></h3>
<p>No. These tools are too bloated and they complicate the build.
</p>
<a name="Why-not-rewrite-FFmpeg-in-object_002doriented-C_002b_002b_003f"></a>
<h3 class="section">4.5 Why not rewrite FFmpeg in object-oriented C++?<span class="pull-right"><a class="anchor hidden-xs" href="#Why-not-rewrite-FFmpeg-in-object_002doriented-C_002b_002b_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Why-not-rewrite-FFmpeg-in-object_002doriented-C_002b_002b_003f" aria-hidden="true">TOC</a></span></h3>
<p>FFmpeg is already organized in a highly modular manner and does not need to
be rewritten in a formal object language. Further, many of the developers
favor straight C; it works for them. For more arguments on this matter,
read <a href="https://web.archive.org/web/20111004021423/http://kernel.org/pub/linux/docs/lkml/#s15">&quot;Programming Religion&quot;</a>.
</p>
<a name="Why-are-the-ffmpeg-programs-devoid-of-debugging-symbols_003f"></a>
<h3 class="section">4.6 Why are the ffmpeg programs devoid of debugging symbols?<span class="pull-right"><a class="anchor hidden-xs" href="#Why-are-the-ffmpeg-programs-devoid-of-debugging-symbols_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Why-are-the-ffmpeg-programs-devoid-of-debugging-symbols_003f" aria-hidden="true">TOC</a></span></h3>
<p>The build process creates <code>ffmpeg_g</code>, <code>ffplay_g</code>, etc. which
contain full debug information. Those binaries are stripped to create
<code>ffmpeg</code>, <code>ffplay</code>, etc. If you need the debug information, use
the *_g versions.
</p>
<a name="I-do-not-like-the-LGPL_002c-can-I-contribute-code-under-the-GPL-instead_003f"></a>
<h3 class="section">4.7 I do not like the LGPL, can I contribute code under the GPL instead?<span class="pull-right"><a class="anchor hidden-xs" href="#I-do-not-like-the-LGPL_002c-can-I-contribute-code-under-the-GPL-instead_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-I-do-not-like-the-LGPL_002c-can-I-contribute-code-under-the-GPL-instead_003f" aria-hidden="true">TOC</a></span></h3>
<p>Yes, as long as the code is optional and can easily and cleanly be placed
under #if CONFIG_GPL without breaking anything. So, for example, a new codec
or filter would be OK under GPL while a bug fix to LGPL code would not.
</p>
<a name="I_0027m-using-FFmpeg-from-within-my-C-application-but-the-linker-complains-about-missing-symbols-from-the-libraries-themselves_002e"></a>
<h3 class="section">4.8 I&rsquo;m using FFmpeg from within my C application but the linker complains about missing symbols from the libraries themselves.<span class="pull-right"><a class="anchor hidden-xs" href="#I_0027m-using-FFmpeg-from-within-my-C-application-but-the-linker-complains-about-missing-symbols-from-the-libraries-themselves_002e" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-I_0027m-using-FFmpeg-from-within-my-C-application-but-the-linker-complains-about-missing-symbols-from-the-libraries-themselves_002e" aria-hidden="true">TOC</a></span></h3>
<p>FFmpeg builds static libraries by default. In static libraries, dependencies
are not handled. That has two consequences. First, you must specify the
libraries in dependency order: <code>-lavdevice</code> must come before
<code>-lavformat</code>, <code>-lavutil</code> must come after everything else, etc.
Second, external libraries that are used in FFmpeg have to be specified too.
</p>
<p>An easy way to get the full list of required libraries in dependency order
is to use <code>pkg-config</code>.
</p>
<div class="example">
<pre class="example">c99 -o program program.c $(pkg-config --cflags --libs libavformat libavcodec)
</pre></div>
<p>See <samp>doc/example/Makefile</samp> and <samp>doc/example/pc-uninstalled</samp> for
more details.
</p>
<a name="I_0027m-using-FFmpeg-from-within-my-C_002b_002b-application-but-the-linker-complains-about-missing-symbols-which-seem-to-be-available_002e"></a>
<h3 class="section">4.9 I&rsquo;m using FFmpeg from within my C++ application but the linker complains about missing symbols which seem to be available.<span class="pull-right"><a class="anchor hidden-xs" href="#I_0027m-using-FFmpeg-from-within-my-C_002b_002b-application-but-the-linker-complains-about-missing-symbols-which-seem-to-be-available_002e" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-I_0027m-using-FFmpeg-from-within-my-C_002b_002b-application-but-the-linker-complains-about-missing-symbols-which-seem-to-be-available_002e" aria-hidden="true">TOC</a></span></h3>
<p>FFmpeg is a pure C project, so to use the libraries within your C++ application
you need to explicitly state that you are using a C library. You can do this by
encompassing your FFmpeg includes using <code>extern &quot;C&quot;</code>.
</p>
<p>See <a href="http://www.parashift.com/c++-faq-lite/mixing-c-and-cpp.html#faq-32.3">http://www.parashift.com/c++-faq-lite/mixing-c-and-cpp.html#faq-32.3</a>
</p>
<a name="I_0027m-using-libavutil-from-within-my-C_002b_002b-application-but-the-compiler-complains-about-_0027UINT64_005fC_0027-was-not-declared-in-this-scope"></a>
<h3 class="section">4.10 I&rsquo;m using libavutil from within my C++ application but the compiler complains about &rsquo;UINT64_C&rsquo; was not declared in this scope<span class="pull-right"><a class="anchor hidden-xs" href="#I_0027m-using-libavutil-from-within-my-C_002b_002b-application-but-the-compiler-complains-about-_0027UINT64_005fC_0027-was-not-declared-in-this-scope" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-I_0027m-using-libavutil-from-within-my-C_002b_002b-application-but-the-compiler-complains-about-_0027UINT64_005fC_0027-was-not-declared-in-this-scope" aria-hidden="true">TOC</a></span></h3>
<p>FFmpeg is a pure C project using C99 math features, in order to enable C++
to use them you have to append -D__STDC_CONSTANT_MACROS to your CXXFLAGS
</p>
<a name="I-have-a-file-in-memory-_002f-a-API-different-from-_002aopen_002f_002aread_002f-libc-how-do-I-use-it-with-libavformat_003f"></a>
<h3 class="section">4.11 I have a file in memory / a API different from *open/*read/ libc how do I use it with libavformat?<span class="pull-right"><a class="anchor hidden-xs" href="#I-have-a-file-in-memory-_002f-a-API-different-from-_002aopen_002f_002aread_002f-libc-how-do-I-use-it-with-libavformat_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-I-have-a-file-in-memory-_002f-a-API-different-from-_002aopen_002f_002aread_002f-libc-how-do-I-use-it-with-libavformat_003f" aria-hidden="true">TOC</a></span></h3>
<p>You have to create a custom AVIOContext using <code>avio_alloc_context</code>,
see <samp>libavformat/aviobuf.c</samp> in FFmpeg and <samp>libmpdemux/demux_lavf.c</samp> in MPlayer or MPlayer2 sources.
</p>
<a name="Where-is-the-documentation-about-ffv1_002c-msmpeg4_002c-asv1_002c-4xm_003f"></a>
<h3 class="section">4.12 Where is the documentation about ffv1, msmpeg4, asv1, 4xm?<span class="pull-right"><a class="anchor hidden-xs" href="#Where-is-the-documentation-about-ffv1_002c-msmpeg4_002c-asv1_002c-4xm_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Where-is-the-documentation-about-ffv1_002c-msmpeg4_002c-asv1_002c-4xm_003f" aria-hidden="true">TOC</a></span></h3>
<p>see <a href="https://www.ffmpeg.org/~michael/">https://www.ffmpeg.org/~michael/</a>
</p>
<a name="How-do-I-feed-H_002e263_002dRTP-_0028and-other-codecs-in-RTP_0029-to-libavcodec_003f"></a>
<h3 class="section">4.13 How do I feed H.263-RTP (and other codecs in RTP) to libavcodec?<span class="pull-right"><a class="anchor hidden-xs" href="#How-do-I-feed-H_002e263_002dRTP-_0028and-other-codecs-in-RTP_0029-to-libavcodec_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-How-do-I-feed-H_002e263_002dRTP-_0028and-other-codecs-in-RTP_0029-to-libavcodec_003f" aria-hidden="true">TOC</a></span></h3>
<p>Even if peculiar since it is network oriented, RTP is a container like any
other. You have to <em>demux</em> RTP before feeding the payload to libavcodec.
In this specific case please look at RFC 4629 to see how it should be done.
</p>
<a name="AVStream_002er_005fframe_005frate-is-wrong_002c-it-is-much-larger-than-the-frame-rate_002e"></a>
<h3 class="section">4.14 AVStream.r_frame_rate is wrong, it is much larger than the frame rate.<span class="pull-right"><a class="anchor hidden-xs" href="#AVStream_002er_005fframe_005frate-is-wrong_002c-it-is-much-larger-than-the-frame-rate_002e" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-AVStream_002er_005fframe_005frate-is-wrong_002c-it-is-much-larger-than-the-frame-rate_002e" aria-hidden="true">TOC</a></span></h3>
<p><code>r_frame_rate</code> is NOT the average frame rate, it is the smallest frame rate
that can accurately represent all timestamps. So no, it is not
wrong if it is larger than the average!
For example, if you have mixed 25 and 30 fps content, then <code>r_frame_rate</code>
will be 150 (it is the least common multiple).
If you are looking for the average frame rate, see <code>AVStream.avg_frame_rate</code>.
</p>
<a name="Why-is-make-fate-not-running-all-tests_003f"></a>
<h3 class="section">4.15 Why is <code>make fate</code> not running all tests?<span class="pull-right"><a class="anchor hidden-xs" href="#Why-is-make-fate-not-running-all-tests_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Why-is-make-fate-not-running-all-tests_003f" aria-hidden="true">TOC</a></span></h3>
<p>Make sure you have the fate-suite samples and the <code>SAMPLES</code> Make variable
or <code>FATE_SAMPLES</code> environment variable or the <code>--samples</code>
<code>configure</code> option is set to the right path.
</p>
<a name="Why-is-make-fate-not-finding-the-samples_003f"></a>
<h3 class="section">4.16 Why is <code>make fate</code> not finding the samples?<span class="pull-right"><a class="anchor hidden-xs" href="#Why-is-make-fate-not-finding-the-samples_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Why-is-make-fate-not-finding-the-samples_003f" aria-hidden="true">TOC</a></span></h3>
<p>Do you happen to have a <code>~</code> character in the samples path to indicate a
home directory? The value is used in ways where the shell cannot expand it,
causing FATE to not find files. Just replace <code>~</code> by the full path.
</p>
<p style="font-size: small;">
This document was generated using <a href="https://www.gnu.org/software/texinfo/"><em>makeinfo</em></a>.
</p>
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FFmpeg Automated Testing Environment
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FFmpeg Automated Testing Environment
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<ul class="no-bullet">
<li><a id="toc-Introduction" href="#Introduction">1 Introduction</a></li>
<li><a id="toc-Using-FATE-from-your-FFmpeg-source-directory" href="#Using-FATE-from-your-FFmpeg-source-directory">2 Using FATE from your FFmpeg source directory</a></li>
<li><a id="toc-Submitting-the-results-to-the-FFmpeg-result-aggregation-server" href="#Submitting-the-results-to-the-FFmpeg-result-aggregation-server">3 Submitting the results to the FFmpeg result aggregation server</a></li>
<li><a id="toc-Uploading-new-samples-to-the-fate-suite" href="#Uploading-new-samples-to-the-fate-suite">4 Uploading new samples to the fate suite</a></li>
<li><a id="toc-FATE-makefile-targets-and-variables" href="#FATE-makefile-targets-and-variables">5 FATE makefile targets and variables</a>
<ul class="no-bullet">
<li><a id="toc-Makefile-targets" href="#Makefile-targets">5.1 Makefile targets</a></li>
<li><a id="toc-Makefile-variables" href="#Makefile-variables">5.2 Makefile variables</a></li>
<li><a id="toc-Examples" href="#Examples">5.3 Examples</a></li>
</ul></li>
</ul>
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</div>
<a name="Introduction"></a>
<h2 class="chapter">1 Introduction<span class="pull-right"><a class="anchor hidden-xs" href="#Introduction" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Introduction" aria-hidden="true">TOC</a></span></h2>
<p>FATE is an extended regression suite on the client-side and a means
for results aggregation and presentation on the server-side.
</p>
<p>The first part of this document explains how you can use FATE from
your FFmpeg source directory to test your ffmpeg binary. The second
part describes how you can run FATE to submit the results to FFmpeg&rsquo;s
FATE server.
</p>
<p>In any way you can have a look at the publicly viewable FATE results
by visiting this website:
</p>
<p><a href="http://fate.ffmpeg.org/">http://fate.ffmpeg.org/</a>
</p>
<p>This is especially recommended for all people contributing source
code to FFmpeg, as it can be seen if some test on some platform broke
with their recent contribution. This usually happens on the platforms
the developers could not test on.
</p>
<p>The second part of this document describes how you can run FATE to
submit your results to FFmpeg&rsquo;s FATE server. If you want to submit your
results be sure to check that your combination of CPU, OS and compiler
is not already listed on the above mentioned website.
</p>
<p>In the third part you can find a comprehensive listing of FATE makefile
targets and variables.
</p>
<a name="Using-FATE-from-your-FFmpeg-source-directory"></a>
<h2 class="chapter">2 Using FATE from your FFmpeg source directory<span class="pull-right"><a class="anchor hidden-xs" href="#Using-FATE-from-your-FFmpeg-source-directory" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Using-FATE-from-your-FFmpeg-source-directory" aria-hidden="true">TOC</a></span></h2>
<p>If you want to run FATE on your machine you need to have the samples
in place. You can get the samples via the build target fate-rsync.
Use this command from the top-level source directory:
</p>
<div class="example">
<pre class="example">make fate-rsync SAMPLES=fate-suite/
make fate SAMPLES=fate-suite/
</pre></div>
<p>The above commands set the samples location by passing a makefile
variable via command line. It is also possible to set the samples
location at source configuration time by invoking configure with
<samp>--samples=&lt;path to the samples directory&gt;</samp>. Afterwards you can
invoke the makefile targets without setting the <var>SAMPLES</var> makefile
variable. This is illustrated by the following commands:
</p>
<div class="example">
<pre class="example">./configure --samples=fate-suite/
make fate-rsync
make fate
</pre></div>
<p>Yet another way to tell FATE about the location of the sample
directory is by making sure the environment variable FATE_SAMPLES
contains the path to your samples directory. This can be achieved
by e.g. putting that variable in your shell profile or by setting
it in your interactive session.
</p>
<div class="example">
<pre class="example">FATE_SAMPLES=fate-suite/ make fate
</pre></div>
<div class="info">
<p>Do not put a &rsquo;~&rsquo; character in the samples path to indicate a home
directory. Because of shell nuances, this will cause FATE to fail.
</p></div>
<p>To get the complete list of tests, run the command:
</p><div class="example">
<pre class="example">make fate-list
</pre></div>
<p>You can specify a subset of tests to run by specifying the
corresponding elements from the list with the <code>fate-</code> prefix,
e.g. as in:
</p><div class="example">
<pre class="example">make fate-ffprobe_compact fate-ffprobe_xml
</pre></div>
<p>This makes it easier to run a few tests in case of failure without
running the complete test suite.
</p>
<p>To use a custom wrapper to run the test, pass <samp>--target-exec</samp> to
<code>configure</code> or set the <var>TARGET_EXEC</var> Make variable.
</p>
<a name="Submitting-the-results-to-the-FFmpeg-result-aggregation-server"></a>
<h2 class="chapter">3 Submitting the results to the FFmpeg result aggregation server<span class="pull-right"><a class="anchor hidden-xs" href="#Submitting-the-results-to-the-FFmpeg-result-aggregation-server" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Submitting-the-results-to-the-FFmpeg-result-aggregation-server" aria-hidden="true">TOC</a></span></h2>
<p>To submit your results to the server you should run fate through the
shell script <samp>tests/fate.sh</samp> from the FFmpeg sources. This script needs
to be invoked with a configuration file as its first argument.
</p>
<div class="example">
<pre class="example">tests/fate.sh /path/to/fate_config
</pre></div>
<p>A configuration file template with comments describing the individual
configuration variables can be found at <samp>doc/fate_config.sh.template</samp>.
</p>
<p>The mentioned configuration template is also available here:
</p><pre class="verbatim">slot= # some unique identifier
repo=git://source.ffmpeg.org/ffmpeg.git # the source repository
#branch=release/2.6 # the branch to test
samples= # path to samples directory
workdir= # directory in which to do all the work
#fate_recv=&quot;ssh -T fate@fate.ffmpeg.org&quot; # command to submit report
comment= # optional description
build_only= # set to &quot;yes&quot; for a compile-only instance that skips tests
ignore_tests=
# the following are optional and map to configure options
arch=
cpu=
cross_prefix=
as=
cc=
ld=
target_os=
sysroot=
target_exec=
target_path=
target_samples=
extra_cflags=
extra_ldflags=
extra_libs=
extra_conf= # extra configure options not covered above
#make= # name of GNU make if not 'make'
makeopts= # extra options passed to 'make'
#makeopts_fate= # extra options passed to 'make' when running tests,
# defaulting to makeopts above if this is not set
#tar= # command to create a tar archive from its arguments on stdout,
# defaults to 'tar c'
</pre>
<p>Create a configuration that suits your needs, based on the configuration
template. The <code>slot</code> configuration variable can be any string that is not
yet used, but it is suggested that you name it adhering to the following
pattern &lsquo;<samp><var>arch</var>-<var>os</var>-<var>compiler</var>-<var>compiler version</var></samp>&rsquo;. The
configuration file itself will be sourced in a shell script, therefore all
shell features may be used. This enables you to setup the environment as you
need it for your build.
</p>
<p>For your first test runs the <code>fate_recv</code> variable should be empty or
commented out. This will run everything as normal except that it will omit
the submission of the results to the server. The following files should be
present in $workdir as specified in the configuration file:
</p>
<ul>
<li> configure.log
</li><li> compile.log
</li><li> test.log
</li><li> report
</li><li> version
</li></ul>
<p>When you have everything working properly you can create an SSH key pair
and send the public key to the FATE server administrator who can be contacted
at the email address <a href="mailto:fate-admin@ffmpeg.org">fate-admin@ffmpeg.org</a>.
</p>
<p>Configure your SSH client to use public key authentication with that key
when connecting to the FATE server. Also do not forget to check the identity
of the server and to accept its host key. This can usually be achieved by
running your SSH client manually and killing it after you accepted the key.
The FATE server&rsquo;s fingerprint is:
</p>
<dl compact="compact">
<dt><span>&lsquo;<samp>RSA</samp>&rsquo;</span></dt>
<dd><p>d3:f1:83:97:a4:75:2b:a6:fb:d6:e8:aa:81:93:97:51
</p></dd>
<dt><span>&lsquo;<samp>ECDSA</samp>&rsquo;</span></dt>
<dd><p>76:9f:68:32:04:1e:d5:d4:ec:47:3f:dc:fc:18:17:86
</p></dd>
</dl>
<p>If you have problems connecting to the FATE server, it may help to try out
the <code>ssh</code> command with one or more <samp>-v</samp> options. You should
get detailed output concerning your SSH configuration and the authentication
process.
</p>
<p>The only thing left is to automate the execution of the fate.sh script and
the synchronisation of the samples directory.
</p>
<a name="Uploading-new-samples-to-the-fate-suite"></a>
<h2 class="chapter">4 Uploading new samples to the fate suite<span class="pull-right"><a class="anchor hidden-xs" href="#Uploading-new-samples-to-the-fate-suite" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Uploading-new-samples-to-the-fate-suite" aria-hidden="true">TOC</a></span></h2>
<p>If you need a sample uploaded send a mail to samples-request.
</p>
<p>This is for developers who have an account on the fate suite server.
If you upload new samples, please make sure they are as small as possible,
space on each client, network bandwidth and so on benefit from smaller test cases.
Also keep in mind older checkouts use existing sample files, that means in
practice generally do not replace, remove or overwrite files as it likely would
break older checkouts or releases.
Also all needed samples for a commit should be uploaded, ideally 24
hours, before the push.
If you need an account for frequently uploading samples or you wish to help
others by doing that send a mail to ffmpeg-devel.
</p>
<div class="example">
<pre class="example">#First update your local samples copy:
rsync -vauL --chmod=Dg+s,Duo+x,ug+rw,o+r,o-w,+X fate-suite.ffmpeg.org:/home/samples/fate-suite/ ~/fate-suite
#Then do a dry run checking what would be uploaded:
rsync -vanL --no-g --chmod=Dg+s,Duo+x,ug+rw,o+r,o-w,+X ~/fate-suite/ fate-suite.ffmpeg.org:/home/samples/fate-suite
#Upload the files:
rsync -vaL --no-g --chmod=Dg+s,Duo+x,ug+rw,o+r,o-w,+X ~/fate-suite/ fate-suite.ffmpeg.org:/home/samples/fate-suite
</pre></div>
<a name="FATE-makefile-targets-and-variables"></a>
<h2 class="chapter">5 FATE makefile targets and variables<span class="pull-right"><a class="anchor hidden-xs" href="#FATE-makefile-targets-and-variables" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-FATE-makefile-targets-and-variables" aria-hidden="true">TOC</a></span></h2>
<a name="Makefile-targets"></a>
<h3 class="section">5.1 Makefile targets<span class="pull-right"><a class="anchor hidden-xs" href="#Makefile-targets" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Makefile-targets" aria-hidden="true">TOC</a></span></h3>
<dl compact="compact">
<dt><span><samp>fate-rsync</samp></span></dt>
<dd><p>Download/synchronize sample files to the configured samples directory.
</p>
</dd>
<dt><span><samp>fate-list</samp></span></dt>
<dd><p>Will list all fate/regression test targets.
</p>
</dd>
<dt><span><samp>fate</samp></span></dt>
<dd><p>Run the FATE test suite (requires the fate-suite dataset).
</p></dd>
</dl>
<a name="Makefile-variables"></a>
<h3 class="section">5.2 Makefile variables<span class="pull-right"><a class="anchor hidden-xs" href="#Makefile-variables" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Makefile-variables" aria-hidden="true">TOC</a></span></h3>
<dl compact="compact">
<dt><span><code>V</code></span></dt>
<dd><p>Verbosity level, can be set to 0, 1 or 2.
</p><ul>
<li> 0: show just the test arguments
</li><li> 1: show just the command used in the test
</li><li> 2: show everything
</li></ul>
</dd>
<dt><span><code>SAMPLES</code></span></dt>
<dd><p>Specify or override the path to the FATE samples at make time, it has a
meaning only while running the regression tests.
</p>
</dd>
<dt><span><code>THREADS</code></span></dt>
<dd><p>Specify how many threads to use while running regression tests, it is
quite useful to detect thread-related regressions.
</p>
</dd>
<dt><span><code>THREAD_TYPE</code></span></dt>
<dd><p>Specify which threading strategy test, either &lsquo;<samp>slice</samp>&rsquo; or &lsquo;<samp>frame</samp>&rsquo;,
by default &lsquo;<samp>slice+frame</samp>&rsquo;
</p>
</dd>
<dt><span><code>CPUFLAGS</code></span></dt>
<dd><p>Specify CPU flags.
</p>
</dd>
<dt><span><code>TARGET_EXEC</code></span></dt>
<dd><p>Specify or override the wrapper used to run the tests.
The <code>TARGET_EXEC</code> option provides a way to run FATE wrapped in
<code>valgrind</code>, <code>qemu-user</code> or <code>wine</code> or on remote targets
through <code>ssh</code>.
</p>
</dd>
<dt><span><code>GEN</code></span></dt>
<dd><p>Set to &lsquo;<samp>1</samp>&rsquo; to generate the missing or mismatched references.
</p>
</dd>
<dt><span><code>HWACCEL</code></span></dt>
<dd><p>Specify which hardware acceleration to use while running regression tests,
by default &lsquo;<samp>none</samp>&rsquo; is used.
</p>
</dd>
<dt><span><code>KEEP</code></span></dt>
<dd><p>Set to &lsquo;<samp>1</samp>&rsquo; to keep temp files generated by fate test(s) when test is successful.
Default is &lsquo;<samp>0</samp>&rsquo;, which removes these files. Files are always kept when a test
fails.
</p>
</dd>
</dl>
<a name="Examples"></a>
<h3 class="section">5.3 Examples<span class="pull-right"><a class="anchor hidden-xs" href="#Examples" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Examples" aria-hidden="true">TOC</a></span></h3>
<div class="example">
<pre class="example">make V=1 SAMPLES=/var/fate/samples THREADS=2 CPUFLAGS=mmx fate
</pre></div>
<p style="font-size: small;">
This document was generated using <a href="https://www.gnu.org/software/texinfo/"><em>makeinfo</em></a>.
</p>
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FFmpeg Resampler Documentation
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FFmpeg Resampler Documentation
</h1>
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<a name="SEC_Top"></a>
<div class="Contents_element" id="SEC_Contents">
<h2 class="contents-heading">Table of Contents</h2>
<div class="contents">
<ul class="no-bullet">
<li><a id="toc-Description" href="#Description">1 Description</a></li>
<li><a id="toc-Resampler-Options" href="#Resampler-Options">2 Resampler Options</a></li>
<li><a id="toc-See-Also" href="#See-Also">3 See Also</a></li>
<li><a id="toc-Authors" href="#Authors">4 Authors</a></li>
</ul>
</div>
</div>
<a name="Description"></a>
<h2 class="chapter">1 Description<span class="pull-right"><a class="anchor hidden-xs" href="#Description" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Description" aria-hidden="true">TOC</a></span></h2>
<p>The FFmpeg resampler provides a high-level interface to the
libswresample library audio resampling utilities. In particular it
allows one to perform audio resampling, audio channel layout rematrixing,
and convert audio format and packing layout.
</p>
<a name="Resampler-Options"></a>
<h2 class="chapter">2 Resampler Options<span class="pull-right"><a class="anchor hidden-xs" href="#Resampler-Options" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Resampler-Options" aria-hidden="true">TOC</a></span></h2>
<p>The audio resampler supports the following named options.
</p>
<p>Options may be set by specifying -<var>option</var> <var>value</var> in the
FFmpeg tools, <var>option</var>=<var>value</var> for the aresample filter,
by setting the value explicitly in the
<code>SwrContext</code> options or using the <samp>libavutil/opt.h</samp> API for
programmatic use.
</p>
<dl compact="compact">
<dt><span><samp>ich, in_channel_count</samp></span></dt>
<dd><p>Set the number of input channels. Default value is 0. Setting this
value is not mandatory if the corresponding channel layout
<samp>in_channel_layout</samp> is set.
</p>
</dd>
<dt><span><samp>och, out_channel_count</samp></span></dt>
<dd><p>Set the number of output channels. Default value is 0. Setting this
value is not mandatory if the corresponding channel layout
<samp>out_channel_layout</samp> is set.
</p>
</dd>
<dt><span><samp>uch, used_channel_count</samp></span></dt>
<dd><p>Set the number of used input channels. Default value is 0. This option is
only used for special remapping.
</p>
</dd>
<dt><span><samp>isr, in_sample_rate</samp></span></dt>
<dd><p>Set the input sample rate. Default value is 0.
</p>
</dd>
<dt><span><samp>osr, out_sample_rate</samp></span></dt>
<dd><p>Set the output sample rate. Default value is 0.
</p>
</dd>
<dt><span><samp>isf, in_sample_fmt</samp></span></dt>
<dd><p>Specify the input sample format. It is set by default to <code>none</code>.
</p>
</dd>
<dt><span><samp>osf, out_sample_fmt</samp></span></dt>
<dd><p>Specify the output sample format. It is set by default to <code>none</code>.
</p>
</dd>
<dt><span><samp>tsf, internal_sample_fmt</samp></span></dt>
<dd><p>Set the internal sample format. Default value is <code>none</code>.
This will automatically be chosen when it is not explicitly set.
</p>
</dd>
<dt><span><samp>icl, in_channel_layout</samp></span></dt>
<dt><span><samp>ocl, out_channel_layout</samp></span></dt>
<dd><p>Set the input/output channel layout.
</p>
<p>See <a data-manual="ffmpeg-utils" href="ffmpeg-utils.html#channel-layout-syntax">(ffmpeg-utils)the Channel Layout section in the ffmpeg-utils(1) manual</a>
for the required syntax.
</p>
</dd>
<dt><span><samp>clev, center_mix_level</samp></span></dt>
<dd><p>Set the center mix level. It is a value expressed in deciBel, and must be
in the interval [-32,32].
</p>
</dd>
<dt><span><samp>slev, surround_mix_level</samp></span></dt>
<dd><p>Set the surround mix level. It is a value expressed in deciBel, and must
be in the interval [-32,32].
</p>
</dd>
<dt><span><samp>lfe_mix_level</samp></span></dt>
<dd><p>Set LFE mix into non LFE level. It is used when there is a LFE input but no
LFE output. It is a value expressed in deciBel, and must
be in the interval [-32,32].
</p>
</dd>
<dt><span><samp>rmvol, rematrix_volume</samp></span></dt>
<dd><p>Set rematrix volume. Default value is 1.0.
</p>
</dd>
<dt><span><samp>rematrix_maxval</samp></span></dt>
<dd><p>Set maximum output value for rematrixing.
This can be used to prevent clipping vs. preventing volume reduction.
A value of 1.0 prevents clipping.
</p>
</dd>
<dt><span><samp>flags, swr_flags</samp></span></dt>
<dd><p>Set flags used by the converter. Default value is 0.
</p>
<p>It supports the following individual flags:
</p><dl compact="compact">
<dt><span><samp>res</samp></span></dt>
<dd><p>force resampling, this flag forces resampling to be used even when the
input and output sample rates match.
</p></dd>
</dl>
</dd>
<dt><span><samp>dither_scale</samp></span></dt>
<dd><p>Set the dither scale. Default value is 1.
</p>
</dd>
<dt><span><samp>dither_method</samp></span></dt>
<dd><p>Set dither method. Default value is 0.
</p>
<p>Supported values:
</p><dl compact="compact">
<dt><span>&lsquo;<samp>rectangular</samp>&rsquo;</span></dt>
<dd><p>select rectangular dither
</p></dd>
<dt><span>&lsquo;<samp>triangular</samp>&rsquo;</span></dt>
<dd><p>select triangular dither
</p></dd>
<dt><span>&lsquo;<samp>triangular_hp</samp>&rsquo;</span></dt>
<dd><p>select triangular dither with high pass
</p></dd>
<dt><span>&lsquo;<samp>lipshitz</samp>&rsquo;</span></dt>
<dd><p>select Lipshitz noise shaping dither.
</p></dd>
<dt><span>&lsquo;<samp>shibata</samp>&rsquo;</span></dt>
<dd><p>select Shibata noise shaping dither.
</p></dd>
<dt><span>&lsquo;<samp>low_shibata</samp>&rsquo;</span></dt>
<dd><p>select low Shibata noise shaping dither.
</p></dd>
<dt><span>&lsquo;<samp>high_shibata</samp>&rsquo;</span></dt>
<dd><p>select high Shibata noise shaping dither.
</p></dd>
<dt><span>&lsquo;<samp>f_weighted</samp>&rsquo;</span></dt>
<dd><p>select f-weighted noise shaping dither
</p></dd>
<dt><span>&lsquo;<samp>modified_e_weighted</samp>&rsquo;</span></dt>
<dd><p>select modified-e-weighted noise shaping dither
</p></dd>
<dt><span>&lsquo;<samp>improved_e_weighted</samp>&rsquo;</span></dt>
<dd><p>select improved-e-weighted noise shaping dither
</p>
</dd>
</dl>
</dd>
<dt><span><samp>resampler</samp></span></dt>
<dd><p>Set resampling engine. Default value is swr.
</p>
<p>Supported values:
</p><dl compact="compact">
<dt><span>&lsquo;<samp>swr</samp>&rsquo;</span></dt>
<dd><p>select the native SW Resampler; filter options precision and cheby are not
applicable in this case.
</p></dd>
<dt><span>&lsquo;<samp>soxr</samp>&rsquo;</span></dt>
<dd><p>select the SoX Resampler (where available); compensation, and filter options
filter_size, phase_shift, exact_rational, filter_type &amp; kaiser_beta, are not
applicable in this case.
</p></dd>
</dl>
</dd>
<dt><span><samp>filter_size</samp></span></dt>
<dd><p>For swr only, set resampling filter size, default value is 32.
</p>
</dd>
<dt><span><samp>phase_shift</samp></span></dt>
<dd><p>For swr only, set resampling phase shift, default value is 10, and must be in
the interval [0,30].
</p>
</dd>
<dt><span><samp>linear_interp</samp></span></dt>
<dd><p>Use linear interpolation when enabled (the default). Disable it if you want
to preserve speed instead of quality when exact_rational fails.
</p>
</dd>
<dt><span><samp>exact_rational</samp></span></dt>
<dd><p>For swr only, when enabled, try to use exact phase_count based on input and
output sample rate. However, if it is larger than <code>1 &lt;&lt; phase_shift</code>,
the phase_count will be <code>1 &lt;&lt; phase_shift</code> as fallback. Default is enabled.
</p>
</dd>
<dt><span><samp>cutoff</samp></span></dt>
<dd><p>Set cutoff frequency (swr: 6dB point; soxr: 0dB point) ratio; must be a float
value between 0 and 1. Default value is 0.97 with swr, and 0.91 with soxr
(which, with a sample-rate of 44100, preserves the entire audio band to 20kHz).
</p>
</dd>
<dt><span><samp>precision</samp></span></dt>
<dd><p>For soxr only, the precision in bits to which the resampled signal will be
calculated. The default value of 20 (which, with suitable dithering, is
appropriate for a destination bit-depth of 16) gives SoX&rsquo;s &rsquo;High Quality&rsquo;; a
value of 28 gives SoX&rsquo;s &rsquo;Very High Quality&rsquo;.
</p>
</dd>
<dt><span><samp>cheby</samp></span></dt>
<dd><p>For soxr only, selects passband rolloff none (Chebyshev) &amp; higher-precision
approximation for &rsquo;irrational&rsquo; ratios. Default value is 0.
</p>
</dd>
<dt><span><samp>async</samp></span></dt>
<dd><p>For swr only, simple 1 parameter audio sync to timestamps using stretching,
squeezing, filling and trimming. Setting this to 1 will enable filling and
trimming, larger values represent the maximum amount in samples that the data
may be stretched or squeezed for each second.
Default value is 0, thus no compensation is applied to make the samples match
the audio timestamps.
</p>
</dd>
<dt><span><samp>first_pts</samp></span></dt>
<dd><p>For swr only, assume the first pts should be this value. The time unit is 1 / sample rate.
This allows for padding/trimming at the start of stream. By default, no
assumption is made about the first frame&rsquo;s expected pts, so no padding or
trimming is done. For example, this could be set to 0 to pad the beginning with
silence if an audio stream starts after the video stream or to trim any samples
with a negative pts due to encoder delay.
</p>
</dd>
<dt><span><samp>min_comp</samp></span></dt>
<dd><p>For swr only, set the minimum difference between timestamps and audio data (in
seconds) to trigger stretching/squeezing/filling or trimming of the
data to make it match the timestamps. The default is that
stretching/squeezing/filling and trimming is disabled
(<samp>min_comp</samp> = <code>FLT_MAX</code>).
</p>
</dd>
<dt><span><samp>min_hard_comp</samp></span></dt>
<dd><p>For swr only, set the minimum difference between timestamps and audio data (in
seconds) to trigger adding/dropping samples to make it match the
timestamps. This option effectively is a threshold to select between
hard (trim/fill) and soft (squeeze/stretch) compensation. Note that
all compensation is by default disabled through <samp>min_comp</samp>.
The default is 0.1.
</p>
</dd>
<dt><span><samp>comp_duration</samp></span></dt>
<dd><p>For swr only, set duration (in seconds) over which data is stretched/squeezed
to make it match the timestamps. Must be a non-negative double float value,
default value is 1.0.
</p>
</dd>
<dt><span><samp>max_soft_comp</samp></span></dt>
<dd><p>For swr only, set maximum factor by which data is stretched/squeezed to make it
match the timestamps. Must be a non-negative double float value, default value
is 0.
</p>
</dd>
<dt><span><samp>matrix_encoding</samp></span></dt>
<dd><p>Select matrixed stereo encoding.
</p>
<p>It accepts the following values:
</p><dl compact="compact">
<dt><span>&lsquo;<samp>none</samp>&rsquo;</span></dt>
<dd><p>select none
</p></dd>
<dt><span>&lsquo;<samp>dolby</samp>&rsquo;</span></dt>
<dd><p>select Dolby
</p></dd>
<dt><span>&lsquo;<samp>dplii</samp>&rsquo;</span></dt>
<dd><p>select Dolby Pro Logic II
</p></dd>
</dl>
<p>Default value is <code>none</code>.
</p>
</dd>
<dt><span><samp>filter_type</samp></span></dt>
<dd><p>For swr only, select resampling filter type. This only affects resampling
operations.
</p>
<p>It accepts the following values:
</p><dl compact="compact">
<dt><span>&lsquo;<samp>cubic</samp>&rsquo;</span></dt>
<dd><p>select cubic
</p></dd>
<dt><span>&lsquo;<samp>blackman_nuttall</samp>&rsquo;</span></dt>
<dd><p>select Blackman Nuttall windowed sinc
</p></dd>
<dt><span>&lsquo;<samp>kaiser</samp>&rsquo;</span></dt>
<dd><p>select Kaiser windowed sinc
</p></dd>
</dl>
</dd>
<dt><span><samp>kaiser_beta</samp></span></dt>
<dd><p>For swr only, set Kaiser window beta value. Must be a double float value in the
interval [2,16], default value is 9.
</p>
</dd>
<dt><span><samp>output_sample_bits</samp></span></dt>
<dd><p>For swr only, set number of used output sample bits for dithering. Must be an integer in the
interval [0,64], default value is 0, which means it&rsquo;s not used.
</p>
</dd>
</dl>
<a name="See-Also"></a>
<h2 class="chapter">3 See Also<span class="pull-right"><a class="anchor hidden-xs" href="#See-Also" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-See-Also" aria-hidden="true">TOC</a></span></h2>
<p><a href="ffmpeg.html">ffmpeg</a>, <a href="ffplay.html">ffplay</a>, <a href="ffprobe.html">ffprobe</a>,
<a href="libswresample.html">libswresample</a>
</p>
<a name="Authors"></a>
<h2 class="chapter">4 Authors<span class="pull-right"><a class="anchor hidden-xs" href="#Authors" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Authors" aria-hidden="true">TOC</a></span></h2>
<p>The FFmpeg developers.
</p>
<p>For details about the authorship, see the Git history of the project
(git://source.ffmpeg.org/ffmpeg), e.g. by typing the command
<code>git log</code> in the FFmpeg source directory, or browsing the
online repository at <a href="http://source.ffmpeg.org">http://source.ffmpeg.org</a>.
</p>
<p>Maintainers for the specific components are listed in the file
<samp>MAINTAINERS</samp> in the source code tree.
</p>
<p style="font-size: small;">
This document was generated using <a href="https://www.gnu.org/software/texinfo/"><em>makeinfo</em></a>.
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FFmpeg Scaler Documentation
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FFmpeg Scaler Documentation
</h1>
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<a name="SEC_Top"></a>
<div class="Contents_element" id="SEC_Contents">
<h2 class="contents-heading">Table of Contents</h2>
<div class="contents">
<ul class="no-bullet">
<li><a id="toc-Description" href="#Description">1 Description</a></li>
<li><a id="toc-Scaler-Options" href="#Scaler-Options">2 Scaler Options</a></li>
<li><a id="toc-See-Also" href="#See-Also">3 See Also</a></li>
<li><a id="toc-Authors" href="#Authors">4 Authors</a></li>
</ul>
</div>
</div>
<a name="Description"></a>
<h2 class="chapter">1 Description<span class="pull-right"><a class="anchor hidden-xs" href="#Description" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Description" aria-hidden="true">TOC</a></span></h2>
<p>The FFmpeg rescaler provides a high-level interface to the libswscale
library image conversion utilities. In particular it allows one to perform
image rescaling and pixel format conversion.
</p>
<span id="scaler_005foptions"></span><a name="Scaler-Options"></a>
<h2 class="chapter">2 Scaler Options<span class="pull-right"><a class="anchor hidden-xs" href="#Scaler-Options" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Scaler-Options" aria-hidden="true">TOC</a></span></h2>
<p>The video scaler supports the following named options.
</p>
<p>Options may be set by specifying -<var>option</var> <var>value</var> in the
FFmpeg tools, with a few API-only exceptions noted below.
For programmatic use, they can be set explicitly in the
<code>SwsContext</code> options or through the <samp>libavutil/opt.h</samp> API.
</p>
<dl compact="compact">
<dd>
<span id="sws_005fflags"></span></dd>
<dt><span><samp>sws_flags</samp></span></dt>
<dd><p>Set the scaler flags. This is also used to set the scaling
algorithm. Only a single algorithm should be selected. Default
value is &lsquo;<samp>bicubic</samp>&rsquo;.
</p>
<p>It accepts the following values:
</p><dl compact="compact">
<dt><span>&lsquo;<samp>fast_bilinear</samp>&rsquo;</span></dt>
<dd><p>Select fast bilinear scaling algorithm.
</p>
</dd>
<dt><span>&lsquo;<samp>bilinear</samp>&rsquo;</span></dt>
<dd><p>Select bilinear scaling algorithm.
</p>
</dd>
<dt><span>&lsquo;<samp>bicubic</samp>&rsquo;</span></dt>
<dd><p>Select bicubic scaling algorithm.
</p>
</dd>
<dt><span>&lsquo;<samp>experimental</samp>&rsquo;</span></dt>
<dd><p>Select experimental scaling algorithm.
</p>
</dd>
<dt><span>&lsquo;<samp>neighbor</samp>&rsquo;</span></dt>
<dd><p>Select nearest neighbor rescaling algorithm.
</p>
</dd>
<dt><span>&lsquo;<samp>area</samp>&rsquo;</span></dt>
<dd><p>Select averaging area rescaling algorithm.
</p>
</dd>
<dt><span>&lsquo;<samp>bicublin</samp>&rsquo;</span></dt>
<dd><p>Select bicubic scaling algorithm for the luma component, bilinear for
chroma components.
</p>
</dd>
<dt><span>&lsquo;<samp>gauss</samp>&rsquo;</span></dt>
<dd><p>Select Gaussian rescaling algorithm.
</p>
</dd>
<dt><span>&lsquo;<samp>sinc</samp>&rsquo;</span></dt>
<dd><p>Select sinc rescaling algorithm.
</p>
</dd>
<dt><span>&lsquo;<samp>lanczos</samp>&rsquo;</span></dt>
<dd><p>Select Lanczos rescaling algorithm. The default width (alpha) is 3 and can be
changed by setting <code>param0</code>.
</p>
</dd>
<dt><span>&lsquo;<samp>spline</samp>&rsquo;</span></dt>
<dd><p>Select natural bicubic spline rescaling algorithm.
</p>
</dd>
<dt><span>&lsquo;<samp>print_info</samp>&rsquo;</span></dt>
<dd><p>Enable printing/debug logging.
</p>
</dd>
<dt><span>&lsquo;<samp>accurate_rnd</samp>&rsquo;</span></dt>
<dd><p>Enable accurate rounding.
</p>
</dd>
<dt><span>&lsquo;<samp>full_chroma_int</samp>&rsquo;</span></dt>
<dd><p>Enable full chroma interpolation.
</p>
</dd>
<dt><span>&lsquo;<samp>full_chroma_inp</samp>&rsquo;</span></dt>
<dd><p>Select full chroma input.
</p>
</dd>
<dt><span>&lsquo;<samp>bitexact</samp>&rsquo;</span></dt>
<dd><p>Enable bitexact output.
</p></dd>
</dl>
</dd>
<dt><span><samp>srcw <var>(API only)</var></samp></span></dt>
<dd><p>Set source width.
</p>
</dd>
<dt><span><samp>srch <var>(API only)</var></samp></span></dt>
<dd><p>Set source height.
</p>
</dd>
<dt><span><samp>dstw <var>(API only)</var></samp></span></dt>
<dd><p>Set destination width.
</p>
</dd>
<dt><span><samp>dsth <var>(API only)</var></samp></span></dt>
<dd><p>Set destination height.
</p>
</dd>
<dt><span><samp>src_format <var>(API only)</var></samp></span></dt>
<dd><p>Set source pixel format (must be expressed as an integer).
</p>
</dd>
<dt><span><samp>dst_format <var>(API only)</var></samp></span></dt>
<dd><p>Set destination pixel format (must be expressed as an integer).
</p>
</dd>
<dt><span><samp>src_range <var>(boolean)</var></samp></span></dt>
<dd><p>If value is set to <code>1</code>, indicates source is full range. Default value is
<code>0</code>, which indicates source is limited range.
</p>
</dd>
<dt><span><samp>dst_range <var>(boolean)</var></samp></span></dt>
<dd><p>If value is set to <code>1</code>, enable full range for destination. Default value
is <code>0</code>, which enables limited range.
</p>
<span id="sws_005fparams"></span></dd>
<dt><span><samp>param0, param1</samp></span></dt>
<dd><p>Set scaling algorithm parameters. The specified values are specific of
some scaling algorithms and ignored by others. The specified values
are floating point number values.
</p>
</dd>
<dt><span><samp>sws_dither</samp></span></dt>
<dd><p>Set the dithering algorithm. Accepts one of the following
values. Default value is &lsquo;<samp>auto</samp>&rsquo;.
</p>
<dl compact="compact">
<dt><span>&lsquo;<samp>auto</samp>&rsquo;</span></dt>
<dd><p>automatic choice
</p>
</dd>
<dt><span>&lsquo;<samp>none</samp>&rsquo;</span></dt>
<dd><p>no dithering
</p>
</dd>
<dt><span>&lsquo;<samp>bayer</samp>&rsquo;</span></dt>
<dd><p>bayer dither
</p>
</dd>
<dt><span>&lsquo;<samp>ed</samp>&rsquo;</span></dt>
<dd><p>error diffusion dither
</p>
</dd>
<dt><span>&lsquo;<samp>a_dither</samp>&rsquo;</span></dt>
<dd><p>arithmetic dither, based using addition
</p>
</dd>
<dt><span>&lsquo;<samp>x_dither</samp>&rsquo;</span></dt>
<dd><p>arithmetic dither, based using xor (more random/less apparent patterning that
a_dither).
</p>
</dd>
</dl>
</dd>
<dt><span><samp>alphablend</samp></span></dt>
<dd><p>Set the alpha blending to use when the input has alpha but the output does not.
Default value is &lsquo;<samp>none</samp>&rsquo;.
</p>
<dl compact="compact">
<dt><span>&lsquo;<samp>uniform_color</samp>&rsquo;</span></dt>
<dd><p>Blend onto a uniform background color
</p>
</dd>
<dt><span>&lsquo;<samp>checkerboard</samp>&rsquo;</span></dt>
<dd><p>Blend onto a checkerboard
</p>
</dd>
<dt><span>&lsquo;<samp>none</samp>&rsquo;</span></dt>
<dd><p>No blending
</p>
</dd>
</dl>
</dd>
</dl>
<a name="See-Also"></a>
<h2 class="chapter">3 See Also<span class="pull-right"><a class="anchor hidden-xs" href="#See-Also" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-See-Also" aria-hidden="true">TOC</a></span></h2>
<p><a href="ffmpeg.html">ffmpeg</a>, <a href="ffplay.html">ffplay</a>, <a href="ffprobe.html">ffprobe</a>,
<a href="libswscale.html">libswscale</a>
</p>
<a name="Authors"></a>
<h2 class="chapter">4 Authors<span class="pull-right"><a class="anchor hidden-xs" href="#Authors" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Authors" aria-hidden="true">TOC</a></span></h2>
<p>The FFmpeg developers.
</p>
<p>For details about the authorship, see the Git history of the project
(git://source.ffmpeg.org/ffmpeg), e.g. by typing the command
<code>git log</code> in the FFmpeg source directory, or browsing the
online repository at <a href="http://source.ffmpeg.org">http://source.ffmpeg.org</a>.
</p>
<p>Maintainers for the specific components are listed in the file
<samp>MAINTAINERS</samp> in the source code tree.
</p>
<p style="font-size: small;">
This document was generated using <a href="https://www.gnu.org/software/texinfo/"><em>makeinfo</em></a>.
</p>
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ffplay Documentation
</title>
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ffplay Documentation
</h1>
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</div>
<a name="SEC_Top"></a>
<div class="Contents_element" id="SEC_Contents">
<h2 class="contents-heading">Table of Contents</h2>
<div class="contents">
<ul class="no-bullet">
<li><a id="toc-Synopsis" href="#Synopsis">1 Synopsis</a></li>
<li><a id="toc-Description" href="#Description">2 Description</a></li>
<li><a id="toc-Options" href="#Options">3 Options</a>
<ul class="no-bullet">
<li><a id="toc-Stream-specifiers-1" href="#Stream-specifiers-1">3.1 Stream specifiers</a></li>
<li><a id="toc-Generic-options" href="#Generic-options">3.2 Generic options</a></li>
<li><a id="toc-AVOptions" href="#AVOptions">3.3 AVOptions</a></li>
<li><a id="toc-Main-options" href="#Main-options">3.4 Main options</a></li>
<li><a id="toc-Advanced-options" href="#Advanced-options">3.5 Advanced options</a></li>
<li><a id="toc-While-playing" href="#While-playing">3.6 While playing</a></li>
</ul></li>
<li><a id="toc-See-Also" href="#See-Also">4 See Also</a></li>
<li><a id="toc-Authors" href="#Authors">5 Authors</a></li>
</ul>
</div>
</div>
<a name="Synopsis"></a>
<h2 class="chapter">1 Synopsis<span class="pull-right"><a class="anchor hidden-xs" href="#Synopsis" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Synopsis" aria-hidden="true">TOC</a></span></h2>
<p>ffplay [<var>options</var>] [<samp>input_url</samp>]
</p>
<a name="Description"></a>
<h2 class="chapter">2 Description<span class="pull-right"><a class="anchor hidden-xs" href="#Description" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Description" aria-hidden="true">TOC</a></span></h2>
<p>FFplay is a very simple and portable media player using the FFmpeg
libraries and the SDL library. It is mostly used as a testbed for the
various FFmpeg APIs.
</p>
<a name="Options"></a>
<h2 class="chapter">3 Options<span class="pull-right"><a class="anchor hidden-xs" href="#Options" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Options" aria-hidden="true">TOC</a></span></h2>
<p>All the numerical options, if not specified otherwise, accept a string
representing a number as input, which may be followed by one of the SI
unit prefixes, for example: &rsquo;K&rsquo;, &rsquo;M&rsquo;, or &rsquo;G&rsquo;.
</p>
<p>If &rsquo;i&rsquo; is appended to the SI unit prefix, the complete prefix will be
interpreted as a unit prefix for binary multiples, which are based on
powers of 1024 instead of powers of 1000. Appending &rsquo;B&rsquo; to the SI unit
prefix multiplies the value by 8. This allows using, for example:
&rsquo;KB&rsquo;, &rsquo;MiB&rsquo;, &rsquo;G&rsquo; and &rsquo;B&rsquo; as number suffixes.
</p>
<p>Options which do not take arguments are boolean options, and set the
corresponding value to true. They can be set to false by prefixing
the option name with &quot;no&quot;. For example using &quot;-nofoo&quot;
will set the boolean option with name &quot;foo&quot; to false.
</p>
<span id="Stream-specifiers"></span><a name="Stream-specifiers-1"></a>
<h3 class="section">3.1 Stream specifiers<span class="pull-right"><a class="anchor hidden-xs" href="#Stream-specifiers-1" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Stream-specifiers-1" aria-hidden="true">TOC</a></span></h3>
<p>Some options are applied per-stream, e.g. bitrate or codec. Stream specifiers
are used to precisely specify which stream(s) a given option belongs to.
</p>
<p>A stream specifier is a string generally appended to the option name and
separated from it by a colon. E.g. <code>-codec:a:1 ac3</code> contains the
<code>a:1</code> stream specifier, which matches the second audio stream. Therefore, it
would select the ac3 codec for the second audio stream.
</p>
<p>A stream specifier can match several streams, so that the option is applied to all
of them. E.g. the stream specifier in <code>-b:a 128k</code> matches all audio
streams.
</p>
<p>An empty stream specifier matches all streams. For example, <code>-codec copy</code>
or <code>-codec: copy</code> would copy all the streams without reencoding.
</p>
<p>Possible forms of stream specifiers are:
</p><dl compact="compact">
<dt><span><samp><var>stream_index</var></samp></span></dt>
<dd><p>Matches the stream with this index. E.g. <code>-threads:1 4</code> would set the
thread count for the second stream to 4. If <var>stream_index</var> is used as an
additional stream specifier (see below), then it selects stream number
<var>stream_index</var> from the matching streams. Stream numbering is based on the
order of the streams as detected by libavformat except when a program ID is
also specified. In this case it is based on the ordering of the streams in the
program.
</p></dd>
<dt><span><samp><var>stream_type</var>[:<var>additional_stream_specifier</var>]</samp></span></dt>
<dd><p><var>stream_type</var> is one of following: &rsquo;v&rsquo; or &rsquo;V&rsquo; for video, &rsquo;a&rsquo; for audio, &rsquo;s&rsquo;
for subtitle, &rsquo;d&rsquo; for data, and &rsquo;t&rsquo; for attachments. &rsquo;v&rsquo; matches all video
streams, &rsquo;V&rsquo; only matches video streams which are not attached pictures, video
thumbnails or cover arts. If <var>additional_stream_specifier</var> is used, then
it matches streams which both have this type and match the
<var>additional_stream_specifier</var>. Otherwise, it matches all streams of the
specified type.
</p></dd>
<dt><span><samp>p:<var>program_id</var>[:<var>additional_stream_specifier</var>]</samp></span></dt>
<dd><p>Matches streams which are in the program with the id <var>program_id</var>. If
<var>additional_stream_specifier</var> is used, then it matches streams which both
are part of the program and match the <var>additional_stream_specifier</var>.
</p>
</dd>
<dt><span><samp>#<var>stream_id</var> or i:<var>stream_id</var></samp></span></dt>
<dd><p>Match the stream by stream id (e.g. PID in MPEG-TS container).
</p></dd>
<dt><span><samp>m:<var>key</var>[:<var>value</var>]</samp></span></dt>
<dd><p>Matches streams with the metadata tag <var>key</var> having the specified value. If
<var>value</var> is not given, matches streams that contain the given tag with any
value.
</p></dd>
<dt><span><samp>u</samp></span></dt>
<dd><p>Matches streams with usable configuration, the codec must be defined and the
essential information such as video dimension or audio sample rate must be present.
</p>
<p>Note that in <code>ffmpeg</code>, matching by metadata will only work properly for
input files.
</p></dd>
</dl>
<a name="Generic-options"></a>
<h3 class="section">3.2 Generic options<span class="pull-right"><a class="anchor hidden-xs" href="#Generic-options" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Generic-options" aria-hidden="true">TOC</a></span></h3>
<p>These options are shared amongst the ff* tools.
</p>
<dl compact="compact">
<dt><span><samp>-L</samp></span></dt>
<dd><p>Show license.
</p>
</dd>
<dt><span><samp>-h, -?, -help, --help [<var>arg</var>]</samp></span></dt>
<dd><p>Show help. An optional parameter may be specified to print help about a specific
item. If no argument is specified, only basic (non advanced) tool
options are shown.
</p>
<p>Possible values of <var>arg</var> are:
</p><dl compact="compact">
<dt><span><samp>long</samp></span></dt>
<dd><p>Print advanced tool options in addition to the basic tool options.
</p>
</dd>
<dt><span><samp>full</samp></span></dt>
<dd><p>Print complete list of options, including shared and private options
for encoders, decoders, demuxers, muxers, filters, etc.
</p>
</dd>
<dt><span><samp>decoder=<var>decoder_name</var></samp></span></dt>
<dd><p>Print detailed information about the decoder named <var>decoder_name</var>. Use the
<samp>-decoders</samp> option to get a list of all decoders.
</p>
</dd>
<dt><span><samp>encoder=<var>encoder_name</var></samp></span></dt>
<dd><p>Print detailed information about the encoder named <var>encoder_name</var>. Use the
<samp>-encoders</samp> option to get a list of all encoders.
</p>
</dd>
<dt><span><samp>demuxer=<var>demuxer_name</var></samp></span></dt>
<dd><p>Print detailed information about the demuxer named <var>demuxer_name</var>. Use the
<samp>-formats</samp> option to get a list of all demuxers and muxers.
</p>
</dd>
<dt><span><samp>muxer=<var>muxer_name</var></samp></span></dt>
<dd><p>Print detailed information about the muxer named <var>muxer_name</var>. Use the
<samp>-formats</samp> option to get a list of all muxers and demuxers.
</p>
</dd>
<dt><span><samp>filter=<var>filter_name</var></samp></span></dt>
<dd><p>Print detailed information about the filter named <var>filter_name</var>. Use the
<samp>-filters</samp> option to get a list of all filters.
</p>
</dd>
<dt><span><samp>bsf=<var>bitstream_filter_name</var></samp></span></dt>
<dd><p>Print detailed information about the bitstream filter named <var>bitstream_filter_name</var>.
Use the <samp>-bsfs</samp> option to get a list of all bitstream filters.
</p>
</dd>
<dt><span><samp>protocol=<var>protocol_name</var></samp></span></dt>
<dd><p>Print detailed information about the protocol named <var>protocol_name</var>.
Use the <samp>-protocols</samp> option to get a list of all protocols.
</p></dd>
</dl>
</dd>
<dt><span><samp>-version</samp></span></dt>
<dd><p>Show version.
</p>
</dd>
<dt><span><samp>-buildconf</samp></span></dt>
<dd><p>Show the build configuration, one option per line.
</p>
</dd>
<dt><span><samp>-formats</samp></span></dt>
<dd><p>Show available formats (including devices).
</p>
</dd>
<dt><span><samp>-demuxers</samp></span></dt>
<dd><p>Show available demuxers.
</p>
</dd>
<dt><span><samp>-muxers</samp></span></dt>
<dd><p>Show available muxers.
</p>
</dd>
<dt><span><samp>-devices</samp></span></dt>
<dd><p>Show available devices.
</p>
</dd>
<dt><span><samp>-codecs</samp></span></dt>
<dd><p>Show all codecs known to libavcodec.
</p>
<p>Note that the term &rsquo;codec&rsquo; is used throughout this documentation as a shortcut
for what is more correctly called a media bitstream format.
</p>
</dd>
<dt><span><samp>-decoders</samp></span></dt>
<dd><p>Show available decoders.
</p>
</dd>
<dt><span><samp>-encoders</samp></span></dt>
<dd><p>Show all available encoders.
</p>
</dd>
<dt><span><samp>-bsfs</samp></span></dt>
<dd><p>Show available bitstream filters.
</p>
</dd>
<dt><span><samp>-protocols</samp></span></dt>
<dd><p>Show available protocols.
</p>
</dd>
<dt><span><samp>-filters</samp></span></dt>
<dd><p>Show available libavfilter filters.
</p>
</dd>
<dt><span><samp>-pix_fmts</samp></span></dt>
<dd><p>Show available pixel formats.
</p>
</dd>
<dt><span><samp>-sample_fmts</samp></span></dt>
<dd><p>Show available sample formats.
</p>
</dd>
<dt><span><samp>-layouts</samp></span></dt>
<dd><p>Show channel names and standard channel layouts.
</p>
</dd>
<dt><span><samp>-dispositions</samp></span></dt>
<dd><p>Show stream dispositions.
</p>
</dd>
<dt><span><samp>-colors</samp></span></dt>
<dd><p>Show recognized color names.
</p>
</dd>
<dt><span><samp>-sources <var>device</var>[,<var>opt1</var>=<var>val1</var>[,<var>opt2</var>=<var>val2</var>]...]</samp></span></dt>
<dd><p>Show autodetected sources of the input device.
Some devices may provide system-dependent source names that cannot be autodetected.
The returned list cannot be assumed to be always complete.
</p><div class="example">
<pre class="example">ffmpeg -sources pulse,server=192.168.0.4
</pre></div>
</dd>
<dt><span><samp>-sinks <var>device</var>[,<var>opt1</var>=<var>val1</var>[,<var>opt2</var>=<var>val2</var>]...]</samp></span></dt>
<dd><p>Show autodetected sinks of the output device.
Some devices may provide system-dependent sink names that cannot be autodetected.
The returned list cannot be assumed to be always complete.
</p><div class="example">
<pre class="example">ffmpeg -sinks pulse,server=192.168.0.4
</pre></div>
</dd>
<dt><span><samp>-loglevel [<var>flags</var>+]<var>loglevel</var> | -v [<var>flags</var>+]<var>loglevel</var></samp></span></dt>
<dd><p>Set logging level and flags used by the library.
</p>
<p>The optional <var>flags</var> prefix can consist of the following values:
</p><dl compact="compact">
<dt><span>&lsquo;<samp>repeat</samp>&rsquo;</span></dt>
<dd><p>Indicates that repeated log output should not be compressed to the first line
and the &quot;Last message repeated n times&quot; line will be omitted.
</p></dd>
<dt><span>&lsquo;<samp>level</samp>&rsquo;</span></dt>
<dd><p>Indicates that log output should add a <code>[level]</code> prefix to each message
line. This can be used as an alternative to log coloring, e.g. when dumping the
log to file.
</p></dd>
</dl>
<p>Flags can also be used alone by adding a &rsquo;+&rsquo;/&rsquo;-&rsquo; prefix to set/reset a single
flag without affecting other <var>flags</var> or changing <var>loglevel</var>. When
setting both <var>flags</var> and <var>loglevel</var>, a &rsquo;+&rsquo; separator is expected
between the last <var>flags</var> value and before <var>loglevel</var>.
</p>
<p><var>loglevel</var> is a string or a number containing one of the following values:
</p><dl compact="compact">
<dt><span>&lsquo;<samp>quiet, -8</samp>&rsquo;</span></dt>
<dd><p>Show nothing at all; be silent.
</p></dd>
<dt><span>&lsquo;<samp>panic, 0</samp>&rsquo;</span></dt>
<dd><p>Only show fatal errors which could lead the process to crash, such as
an assertion failure. This is not currently used for anything.
</p></dd>
<dt><span>&lsquo;<samp>fatal, 8</samp>&rsquo;</span></dt>
<dd><p>Only show fatal errors. These are errors after which the process absolutely
cannot continue.
</p></dd>
<dt><span>&lsquo;<samp>error, 16</samp>&rsquo;</span></dt>
<dd><p>Show all errors, including ones which can be recovered from.
</p></dd>
<dt><span>&lsquo;<samp>warning, 24</samp>&rsquo;</span></dt>
<dd><p>Show all warnings and errors. Any message related to possibly
incorrect or unexpected events will be shown.
</p></dd>
<dt><span>&lsquo;<samp>info, 32</samp>&rsquo;</span></dt>
<dd><p>Show informative messages during processing. This is in addition to
warnings and errors. This is the default value.
</p></dd>
<dt><span>&lsquo;<samp>verbose, 40</samp>&rsquo;</span></dt>
<dd><p>Same as <code>info</code>, except more verbose.
</p></dd>
<dt><span>&lsquo;<samp>debug, 48</samp>&rsquo;</span></dt>
<dd><p>Show everything, including debugging information.
</p></dd>
<dt><span>&lsquo;<samp>trace, 56</samp>&rsquo;</span></dt>
</dl>
<p>For example to enable repeated log output, add the <code>level</code> prefix, and set
<var>loglevel</var> to <code>verbose</code>:
</p><div class="example">
<pre class="example">ffmpeg -loglevel repeat+level+verbose -i input output
</pre></div>
<p>Another example that enables repeated log output without affecting current
state of <code>level</code> prefix flag or <var>loglevel</var>:
</p><div class="example">
<pre class="example">ffmpeg [...] -loglevel +repeat
</pre></div>
<p>By default the program logs to stderr. If coloring is supported by the
terminal, colors are used to mark errors and warnings. Log coloring
can be disabled setting the environment variable
<code>AV_LOG_FORCE_NOCOLOR</code>, or can be forced setting
the environment variable <code>AV_LOG_FORCE_COLOR</code>.
</p>
</dd>
<dt><span><samp>-report</samp></span></dt>
<dd><p>Dump full command line and log output to a file named
<code><var>program</var>-<var>YYYYMMDD</var>-<var>HHMMSS</var>.log</code> in the current
directory.
This file can be useful for bug reports.
It also implies <code>-loglevel debug</code>.
</p>
<p>Setting the environment variable <code>FFREPORT</code> to any value has the
same effect. If the value is a &rsquo;:&rsquo;-separated key=value sequence, these
options will affect the report; option values must be escaped if they
contain special characters or the options delimiter &rsquo;:&rsquo; (see the
&ldquo;Quoting and escaping&rdquo; section in the ffmpeg-utils manual).
</p>
<p>The following options are recognized:
</p><dl compact="compact">
<dt><span><samp>file</samp></span></dt>
<dd><p>set the file name to use for the report; <code>%p</code> is expanded to the name
of the program, <code>%t</code> is expanded to a timestamp, <code>%%</code> is expanded
to a plain <code>%</code>
</p></dd>
<dt><span><samp>level</samp></span></dt>
<dd><p>set the log verbosity level using a numerical value (see <code>-loglevel</code>).
</p></dd>
</dl>
<p>For example, to output a report to a file named <samp>ffreport.log</samp>
using a log level of <code>32</code> (alias for log level <code>info</code>):
</p>
<div class="example">
<pre class="example">FFREPORT=file=ffreport.log:level=32 ffmpeg -i input output
</pre></div>
<p>Errors in parsing the environment variable are not fatal, and will not
appear in the report.
</p>
</dd>
<dt><span><samp>-hide_banner</samp></span></dt>
<dd><p>Suppress printing banner.
</p>
<p>All FFmpeg tools will normally show a copyright notice, build options
and library versions. This option can be used to suppress printing
this information.
</p>
</dd>
<dt><span><samp>-cpuflags flags (<em>global</em>)</samp></span></dt>
<dd><p>Allows setting and clearing cpu flags. This option is intended
for testing. Do not use it unless you know what you&rsquo;re doing.
</p><div class="example">
<pre class="example">ffmpeg -cpuflags -sse+mmx ...
ffmpeg -cpuflags mmx ...
ffmpeg -cpuflags 0 ...
</pre></div>
<p>Possible flags for this option are:
</p><dl compact="compact">
<dt><span>&lsquo;<samp>x86</samp>&rsquo;</span></dt>
<dd><dl compact="compact">
<dt><span>&lsquo;<samp>mmx</samp>&rsquo;</span></dt>
<dt><span>&lsquo;<samp>mmxext</samp>&rsquo;</span></dt>
<dt><span>&lsquo;<samp>sse</samp>&rsquo;</span></dt>
<dt><span>&lsquo;<samp>sse2</samp>&rsquo;</span></dt>
<dt><span>&lsquo;<samp>sse2slow</samp>&rsquo;</span></dt>
<dt><span>&lsquo;<samp>sse3</samp>&rsquo;</span></dt>
<dt><span>&lsquo;<samp>sse3slow</samp>&rsquo;</span></dt>
<dt><span>&lsquo;<samp>ssse3</samp>&rsquo;</span></dt>
<dt><span>&lsquo;<samp>atom</samp>&rsquo;</span></dt>
<dt><span>&lsquo;<samp>sse4.1</samp>&rsquo;</span></dt>
<dt><span>&lsquo;<samp>sse4.2</samp>&rsquo;</span></dt>
<dt><span>&lsquo;<samp>avx</samp>&rsquo;</span></dt>
<dt><span>&lsquo;<samp>avx2</samp>&rsquo;</span></dt>
<dt><span>&lsquo;<samp>xop</samp>&rsquo;</span></dt>
<dt><span>&lsquo;<samp>fma3</samp>&rsquo;</span></dt>
<dt><span>&lsquo;<samp>fma4</samp>&rsquo;</span></dt>
<dt><span>&lsquo;<samp>3dnow</samp>&rsquo;</span></dt>
<dt><span>&lsquo;<samp>3dnowext</samp>&rsquo;</span></dt>
<dt><span>&lsquo;<samp>bmi1</samp>&rsquo;</span></dt>
<dt><span>&lsquo;<samp>bmi2</samp>&rsquo;</span></dt>
<dt><span>&lsquo;<samp>cmov</samp>&rsquo;</span></dt>
</dl>
</dd>
<dt><span>&lsquo;<samp>ARM</samp>&rsquo;</span></dt>
<dd><dl compact="compact">
<dt><span>&lsquo;<samp>armv5te</samp>&rsquo;</span></dt>
<dt><span>&lsquo;<samp>armv6</samp>&rsquo;</span></dt>
<dt><span>&lsquo;<samp>armv6t2</samp>&rsquo;</span></dt>
<dt><span>&lsquo;<samp>vfp</samp>&rsquo;</span></dt>
<dt><span>&lsquo;<samp>vfpv3</samp>&rsquo;</span></dt>
<dt><span>&lsquo;<samp>neon</samp>&rsquo;</span></dt>
<dt><span>&lsquo;<samp>setend</samp>&rsquo;</span></dt>
</dl>
</dd>
<dt><span>&lsquo;<samp>AArch64</samp>&rsquo;</span></dt>
<dd><dl compact="compact">
<dt><span>&lsquo;<samp>armv8</samp>&rsquo;</span></dt>
<dt><span>&lsquo;<samp>vfp</samp>&rsquo;</span></dt>
<dt><span>&lsquo;<samp>neon</samp>&rsquo;</span></dt>
</dl>
</dd>
<dt><span>&lsquo;<samp>PowerPC</samp>&rsquo;</span></dt>
<dd><dl compact="compact">
<dt><span>&lsquo;<samp>altivec</samp>&rsquo;</span></dt>
</dl>
</dd>
<dt><span>&lsquo;<samp>Specific Processors</samp>&rsquo;</span></dt>
<dd><dl compact="compact">
<dt><span>&lsquo;<samp>pentium2</samp>&rsquo;</span></dt>
<dt><span>&lsquo;<samp>pentium3</samp>&rsquo;</span></dt>
<dt><span>&lsquo;<samp>pentium4</samp>&rsquo;</span></dt>
<dt><span>&lsquo;<samp>k6</samp>&rsquo;</span></dt>
<dt><span>&lsquo;<samp>k62</samp>&rsquo;</span></dt>
<dt><span>&lsquo;<samp>athlon</samp>&rsquo;</span></dt>
<dt><span>&lsquo;<samp>athlonxp</samp>&rsquo;</span></dt>
<dt><span>&lsquo;<samp>k8</samp>&rsquo;</span></dt>
</dl>
</dd>
</dl>
</dd>
<dt><span><samp>-cpucount <var>count</var> (<em>global</em>)</samp></span></dt>
<dd><p>Override detection of CPU count. This option is intended
for testing. Do not use it unless you know what you&rsquo;re doing.
</p><div class="example">
<pre class="example">ffmpeg -cpucount 2
</pre></div>
</dd>
<dt><span><samp>-max_alloc <var>bytes</var></samp></span></dt>
<dd><p>Set the maximum size limit for allocating a block on the heap by ffmpeg&rsquo;s
family of malloc functions. Exercise <strong>extreme caution</strong> when using
this option. Don&rsquo;t use if you do not understand the full consequence of doing so.
Default is INT_MAX.
</p></dd>
</dl>
<a name="AVOptions"></a>
<h3 class="section">3.3 AVOptions<span class="pull-right"><a class="anchor hidden-xs" href="#AVOptions" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-AVOptions" aria-hidden="true">TOC</a></span></h3>
<p>These options are provided directly by the libavformat, libavdevice and
libavcodec libraries. To see the list of available AVOptions, use the
<samp>-help</samp> option. They are separated into two categories:
</p><dl compact="compact">
<dt><span><samp>generic</samp></span></dt>
<dd><p>These options can be set for any container, codec or device. Generic options
are listed under AVFormatContext options for containers/devices and under
AVCodecContext options for codecs.
</p></dd>
<dt><span><samp>private</samp></span></dt>
<dd><p>These options are specific to the given container, device or codec. Private
options are listed under their corresponding containers/devices/codecs.
</p></dd>
</dl>
<p>For example to write an ID3v2.3 header instead of a default ID3v2.4 to
an MP3 file, use the <samp>id3v2_version</samp> private option of the MP3
muxer:
</p><div class="example">
<pre class="example">ffmpeg -i input.flac -id3v2_version 3 out.mp3
</pre></div>
<p>All codec AVOptions are per-stream, and thus a stream specifier
should be attached to them:
</p><div class="example">
<pre class="example">ffmpeg -i multichannel.mxf -map 0:v:0 -map 0:a:0 -map 0:a:0 -c:a:0 ac3 -b:a:0 640k -ac:a:1 2 -c:a:1 aac -b:2 128k out.mp4
</pre></div>
<p>In the above example, a multichannel audio stream is mapped twice for output.
The first instance is encoded with codec ac3 and bitrate 640k.
The second instance is downmixed to 2 channels and encoded with codec aac. A bitrate of 128k is specified for it using
absolute index of the output stream.
</p>
<p>Note: the <samp>-nooption</samp> syntax cannot be used for boolean
AVOptions, use <samp>-option 0</samp>/<samp>-option 1</samp>.
</p>
<p>Note: the old undocumented way of specifying per-stream AVOptions by
prepending v/a/s to the options name is now obsolete and will be
removed soon.
</p>
<a name="Main-options"></a>
<h3 class="section">3.4 Main options<span class="pull-right"><a class="anchor hidden-xs" href="#Main-options" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Main-options" aria-hidden="true">TOC</a></span></h3>
<dl compact="compact">
<dt><span><samp>-x <var>width</var></samp></span></dt>
<dd><p>Force displayed width.
</p></dd>
<dt><span><samp>-y <var>height</var></samp></span></dt>
<dd><p>Force displayed height.
</p></dd>
<dt><span><samp>-fs</samp></span></dt>
<dd><p>Start in fullscreen mode.
</p></dd>
<dt><span><samp>-an</samp></span></dt>
<dd><p>Disable audio.
</p></dd>
<dt><span><samp>-vn</samp></span></dt>
<dd><p>Disable video.
</p></dd>
<dt><span><samp>-sn</samp></span></dt>
<dd><p>Disable subtitles.
</p></dd>
<dt><span><samp>-ss <var>pos</var></samp></span></dt>
<dd><p>Seek to <var>pos</var>. Note that in most formats it is not possible to seek
exactly, so <code>ffplay</code> will seek to the nearest seek point to
<var>pos</var>.
</p>
<p><var>pos</var> must be a time duration specification,
see <a data-manual="ffmpeg-utils" href="ffmpeg-utils.html#time-duration-syntax">(ffmpeg-utils)the Time duration section in the ffmpeg-utils(1) manual</a>.
</p></dd>
<dt><span><samp>-t <var>duration</var></samp></span></dt>
<dd><p>Play <var>duration</var> seconds of audio/video.
</p>
<p><var>duration</var> must be a time duration specification,
see <a data-manual="ffmpeg-utils" href="ffmpeg-utils.html#time-duration-syntax">(ffmpeg-utils)the Time duration section in the ffmpeg-utils(1) manual</a>.
</p></dd>
<dt><span><samp>-bytes</samp></span></dt>
<dd><p>Seek by bytes.
</p></dd>
<dt><span><samp>-seek_interval</samp></span></dt>
<dd><p>Set custom interval, in seconds, for seeking using left/right keys. Default is 10 seconds.
</p></dd>
<dt><span><samp>-nodisp</samp></span></dt>
<dd><p>Disable graphical display.
</p></dd>
<dt><span><samp>-noborder</samp></span></dt>
<dd><p>Borderless window.
</p></dd>
<dt><span><samp>-alwaysontop</samp></span></dt>
<dd><p>Window always on top. Available on: X11 with SDL &gt;= 2.0.5, Windows SDL &gt;= 2.0.6.
</p></dd>
<dt><span><samp>-volume</samp></span></dt>
<dd><p>Set the startup volume. 0 means silence, 100 means no volume reduction or
amplification. Negative values are treated as 0, values above 100 are treated
as 100.
</p></dd>
<dt><span><samp>-f <var>fmt</var></samp></span></dt>
<dd><p>Force format.
</p></dd>
<dt><span><samp>-window_title <var>title</var></samp></span></dt>
<dd><p>Set window title (default is the input filename).
</p></dd>
<dt><span><samp>-left <var>title</var></samp></span></dt>
<dd><p>Set the x position for the left of the window (default is a centered window).
</p></dd>
<dt><span><samp>-top <var>title</var></samp></span></dt>
<dd><p>Set the y position for the top of the window (default is a centered window).
</p></dd>
<dt><span><samp>-loop <var>number</var></samp></span></dt>
<dd><p>Loops movie playback &lt;number&gt; times. 0 means forever.
</p></dd>
<dt><span><samp>-showmode <var>mode</var></samp></span></dt>
<dd><p>Set the show mode to use.
Available values for <var>mode</var> are:
</p><dl compact="compact">
<dt><span>&lsquo;<samp>0, video</samp>&rsquo;</span></dt>
<dd><p>show video
</p></dd>
<dt><span>&lsquo;<samp>1, waves</samp>&rsquo;</span></dt>
<dd><p>show audio waves
</p></dd>
<dt><span>&lsquo;<samp>2, rdft</samp>&rsquo;</span></dt>
<dd><p>show audio frequency band using RDFT ((Inverse) Real Discrete Fourier Transform)
</p></dd>
</dl>
<p>Default value is &quot;video&quot;, if video is not present or cannot be played
&quot;rdft&quot; is automatically selected.
</p>
<p>You can interactively cycle through the available show modes by
pressing the key <tt class="key">w</tt>.
</p>
</dd>
<dt><span><samp>-vf <var>filtergraph</var></samp></span></dt>
<dd><p>Create the filtergraph specified by <var>filtergraph</var> and use it to
filter the video stream.
</p>
<p><var>filtergraph</var> is a description of the filtergraph to apply to
the stream, and must have a single video input and a single video
output. In the filtergraph, the input is associated to the label
<code>in</code>, and the output to the label <code>out</code>. See the
ffmpeg-filters manual for more information about the filtergraph
syntax.
</p>
<p>You can specify this parameter multiple times and cycle through the specified
filtergraphs along with the show modes by pressing the key <tt class="key">w</tt>.
</p>
</dd>
<dt><span><samp>-af <var>filtergraph</var></samp></span></dt>
<dd><p><var>filtergraph</var> is a description of the filtergraph to apply to
the input audio.
Use the option &quot;-filters&quot; to show all the available filters (including
sources and sinks).
</p>
</dd>
<dt><span><samp>-i <var>input_url</var></samp></span></dt>
<dd><p>Read <var>input_url</var>.
</p></dd>
</dl>
<a name="Advanced-options"></a>
<h3 class="section">3.5 Advanced options<span class="pull-right"><a class="anchor hidden-xs" href="#Advanced-options" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Advanced-options" aria-hidden="true">TOC</a></span></h3>
<dl compact="compact">
<dt><span><samp>-stats</samp></span></dt>
<dd><p>Print several playback statistics, in particular show the stream
duration, the codec parameters, the current position in the stream and
the audio/video synchronisation drift. It is shown by default, unless the
log level is lower than <code>info</code>. Its display can be forced by manually
specifying this option. To disable it, you need to specify <code>-nostats</code>.
</p>
</dd>
<dt><span><samp>-fast</samp></span></dt>
<dd><p>Non-spec-compliant optimizations.
</p></dd>
<dt><span><samp>-genpts</samp></span></dt>
<dd><p>Generate pts.
</p></dd>
<dt><span><samp>-sync <var>type</var></samp></span></dt>
<dd><p>Set the master clock to audio (<code>type=audio</code>), video
(<code>type=video</code>) or external (<code>type=ext</code>). Default is audio. The
master clock is used to control audio-video synchronization. Most media
players use audio as master clock, but in some cases (streaming or high
quality broadcast) it is necessary to change that. This option is mainly
used for debugging purposes.
</p></dd>
<dt><span><samp>-ast <var>audio_stream_specifier</var></samp></span></dt>
<dd><p>Select the desired audio stream using the given stream specifier. The stream
specifiers are described in the <a href="#Stream-specifiers">Stream specifiers</a> chapter. If this option
is not specified, the &quot;best&quot; audio stream is selected in the program of the
already selected video stream.
</p></dd>
<dt><span><samp>-vst <var>video_stream_specifier</var></samp></span></dt>
<dd><p>Select the desired video stream using the given stream specifier. The stream
specifiers are described in the <a href="#Stream-specifiers">Stream specifiers</a> chapter. If this option
is not specified, the &quot;best&quot; video stream is selected.
</p></dd>
<dt><span><samp>-sst <var>subtitle_stream_specifier</var></samp></span></dt>
<dd><p>Select the desired subtitle stream using the given stream specifier. The stream
specifiers are described in the <a href="#Stream-specifiers">Stream specifiers</a> chapter. If this option
is not specified, the &quot;best&quot; subtitle stream is selected in the program of the
already selected video or audio stream.
</p></dd>
<dt><span><samp>-autoexit</samp></span></dt>
<dd><p>Exit when video is done playing.
</p></dd>
<dt><span><samp>-exitonkeydown</samp></span></dt>
<dd><p>Exit if any key is pressed.
</p></dd>
<dt><span><samp>-exitonmousedown</samp></span></dt>
<dd><p>Exit if any mouse button is pressed.
</p>
</dd>
<dt><span><samp>-codec:<var>media_specifier</var> <var>codec_name</var></samp></span></dt>
<dd><p>Force a specific decoder implementation for the stream identified by
<var>media_specifier</var>, which can assume the values <code>a</code> (audio),
<code>v</code> (video), and <code>s</code> subtitle.
</p>
</dd>
<dt><span><samp>-acodec <var>codec_name</var></samp></span></dt>
<dd><p>Force a specific audio decoder.
</p>
</dd>
<dt><span><samp>-vcodec <var>codec_name</var></samp></span></dt>
<dd><p>Force a specific video decoder.
</p>
</dd>
<dt><span><samp>-scodec <var>codec_name</var></samp></span></dt>
<dd><p>Force a specific subtitle decoder.
</p>
</dd>
<dt><span><samp>-autorotate</samp></span></dt>
<dd><p>Automatically rotate the video according to file metadata. Enabled by
default, use <samp>-noautorotate</samp> to disable it.
</p>
</dd>
<dt><span><samp>-framedrop</samp></span></dt>
<dd><p>Drop video frames if video is out of sync. Enabled by default if the master
clock is not set to video. Use this option to enable frame dropping for all
master clock sources, use <samp>-noframedrop</samp> to disable it.
</p>
</dd>
<dt><span><samp>-infbuf</samp></span></dt>
<dd><p>Do not limit the input buffer size, read as much data as possible from the
input as soon as possible. Enabled by default for realtime streams, where data
may be dropped if not read in time. Use this option to enable infinite buffers
for all inputs, use <samp>-noinfbuf</samp> to disable it.
</p>
</dd>
<dt><span><samp>-filter_threads <var>nb_threads</var></samp></span></dt>
<dd><p>Defines how many threads are used to process a filter pipeline. Each pipeline
will produce a thread pool with this many threads available for parallel
processing. The default is 0 which means that the thread count will be
determined by the number of available CPUs.
</p>
</dd>
</dl>
<a name="While-playing"></a>
<h3 class="section">3.6 While playing<span class="pull-right"><a class="anchor hidden-xs" href="#While-playing" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-While-playing" aria-hidden="true">TOC</a></span></h3>
<dl compact="compact">
<dt><span><tt class="key">q, ESC</tt></span></dt>
<dd><p>Quit.
</p>
</dd>
<dt><span><tt class="key">f</tt></span></dt>
<dd><p>Toggle full screen.
</p>
</dd>
<dt><span><tt class="key">p, SPC</tt></span></dt>
<dd><p>Pause.
</p>
</dd>
<dt><span><tt class="key">m</tt></span></dt>
<dd><p>Toggle mute.
</p>
</dd>
<dt><span><tt class="key">9, 0</tt></span></dt>
<dt><span><tt class="key">/, *</tt></span></dt>
<dd><p>Decrease and increase volume respectively.
</p>
</dd>
<dt><span><tt class="key">a</tt></span></dt>
<dd><p>Cycle audio channel in the current program.
</p>
</dd>
<dt><span><tt class="key">v</tt></span></dt>
<dd><p>Cycle video channel.
</p>
</dd>
<dt><span><tt class="key">t</tt></span></dt>
<dd><p>Cycle subtitle channel in the current program.
</p>
</dd>
<dt><span><tt class="key">c</tt></span></dt>
<dd><p>Cycle program.
</p>
</dd>
<dt><span><tt class="key">w</tt></span></dt>
<dd><p>Cycle video filters or show modes.
</p>
</dd>
<dt><span><tt class="key">s</tt></span></dt>
<dd><p>Step to the next frame.
</p>
<p>Pause if the stream is not already paused, step to the next video
frame, and pause.
</p>
</dd>
<dt><span><tt class="key">left/right</tt></span></dt>
<dd><p>Seek backward/forward 10 seconds.
</p>
</dd>
<dt><span><tt class="key">down/up</tt></span></dt>
<dd><p>Seek backward/forward 1 minute.
</p>
</dd>
<dt><span><tt class="key">page down/page up</tt></span></dt>
<dd><p>Seek to the previous/next chapter.
or if there are no chapters
Seek backward/forward 10 minutes.
</p>
</dd>
<dt><span><tt class="key">right mouse click</tt></span></dt>
<dd><p>Seek to percentage in file corresponding to fraction of width.
</p>
</dd>
<dt><span><tt class="key">left mouse double-click</tt></span></dt>
<dd><p>Toggle full screen.
</p>
</dd>
</dl>
<a name="See-Also"></a>
<h2 class="chapter">4 See Also<span class="pull-right"><a class="anchor hidden-xs" href="#See-Also" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-See-Also" aria-hidden="true">TOC</a></span></h2>
<p><a href="ffplay-all.html">ffmpeg-all</a>,
<a href="ffmpeg.html">ffmpeg</a>, <a href="ffprobe.html">ffprobe</a>,
<a href="ffmpeg-utils.html">ffmpeg-utils</a>,
<a href="ffmpeg-scaler.html">ffmpeg-scaler</a>,
<a href="ffmpeg-resampler.html">ffmpeg-resampler</a>,
<a href="ffmpeg-codecs.html">ffmpeg-codecs</a>,
<a href="ffmpeg-bitstream-filters.html">ffmpeg-bitstream-filters</a>,
<a href="ffmpeg-formats.html">ffmpeg-formats</a>,
<a href="ffmpeg-devices.html">ffmpeg-devices</a>,
<a href="ffmpeg-protocols.html">ffmpeg-protocols</a>,
<a href="ffmpeg-filters.html">ffmpeg-filters</a>
</p>
<a name="Authors"></a>
<h2 class="chapter">5 Authors<span class="pull-right"><a class="anchor hidden-xs" href="#Authors" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Authors" aria-hidden="true">TOC</a></span></h2>
<p>The FFmpeg developers.
</p>
<p>For details about the authorship, see the Git history of the project
(git://source.ffmpeg.org/ffmpeg), e.g. by typing the command
<code>git log</code> in the FFmpeg source directory, or browsing the
online repository at <a href="http://source.ffmpeg.org">http://source.ffmpeg.org</a>.
</p>
<p>Maintainers for the specific components are listed in the file
<samp>MAINTAINERS</samp> in the source code tree.
</p>
<p style="font-size: small;">
This document was generated using <a href="https://www.gnu.org/software/texinfo/"><em>makeinfo</em></a>.
</p>
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Using Git to develop FFmpeg
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<h1>
Using Git to develop FFmpeg
</h1>
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<a name="SEC_Top"></a>
<div class="Contents_element" id="SEC_Contents">
<h2 class="contents-heading">Table of Contents</h2>
<div class="contents">
<ul class="no-bullet">
<li><a id="toc-Introduction" href="#Introduction">1 Introduction</a></li>
<li><a id="toc-Basics-Usage" href="#Basics-Usage">2 Basics Usage</a>
<ul class="no-bullet">
<li><a id="toc-Get-Git" href="#Get-Git">2.1 Get Git</a></li>
<li><a id="toc-Cloning-the-source-tree" href="#Cloning-the-source-tree">2.2 Cloning the source tree</a></li>
<li><a id="toc-Updating-the-source-tree-to-the-latest-revision-1" href="#Updating-the-source-tree-to-the-latest-revision-1">2.3 Updating the source tree to the latest revision</a></li>
<li><a id="toc-Rebasing-your-local-branches" href="#Rebasing-your-local-branches">2.4 Rebasing your local branches</a></li>
<li><a id="toc-Adding_002fremoving-files_002fdirectories" href="#Adding_002fremoving-files_002fdirectories">2.5 Adding/removing files/directories</a></li>
<li><a id="toc-Showing-modifications" href="#Showing-modifications">2.6 Showing modifications</a></li>
<li><a id="toc-Inspecting-the-changelog" href="#Inspecting-the-changelog">2.7 Inspecting the changelog</a></li>
<li><a id="toc-Checking-source-tree-status" href="#Checking-source-tree-status">2.8 Checking source tree status</a></li>
<li><a id="toc-Committing" href="#Committing">2.9 Committing</a></li>
<li><a id="toc-Writing-a-commit-message" href="#Writing-a-commit-message">2.10 Writing a commit message</a></li>
<li><a id="toc-Preparing-a-patchset" href="#Preparing-a-patchset">2.11 Preparing a patchset</a></li>
<li><a id="toc-Sending-patches-for-review" href="#Sending-patches-for-review">2.12 Sending patches for review</a></li>
<li><a id="toc-Renaming_002fmoving_002fcopying-files-or-contents-of-files" href="#Renaming_002fmoving_002fcopying-files-or-contents-of-files">2.13 Renaming/moving/copying files or contents of files</a></li>
</ul></li>
<li><a id="toc-Git-configuration" href="#Git-configuration">3 Git configuration</a>
<ul class="no-bullet">
<li><a id="toc-Personal-Git-installation" href="#Personal-Git-installation">3.1 Personal Git installation</a></li>
<li><a id="toc-Repository-configuration" href="#Repository-configuration">3.2 Repository configuration</a></li>
</ul></li>
<li><a id="toc-FFmpeg-specific" href="#FFmpeg-specific">4 FFmpeg specific</a>
<ul class="no-bullet">
<li><a id="toc-Reverting-broken-commits" href="#Reverting-broken-commits">4.1 Reverting broken commits</a></li>
<li><a id="toc-Pushing-changes-to-remote-trees" href="#Pushing-changes-to-remote-trees">4.2 Pushing changes to remote trees</a></li>
<li><a id="toc-Finding-a-specific-svn-revision" href="#Finding-a-specific-svn-revision">4.3 Finding a specific svn revision</a></li>
</ul></li>
<li><a id="toc-gpg-key-generation" href="#gpg-key-generation">5 gpg key generation</a></li>
<li><a id="toc-Pre_002dpush-checklist" href="#Pre_002dpush-checklist">6 Pre-push checklist</a></li>
<li><a id="toc-Server-Issues" href="#Server-Issues">7 Server Issues</a></li>
</ul>
</div>
</div>
<a name="Introduction"></a>
<h2 class="chapter">1 Introduction<span class="pull-right"><a class="anchor hidden-xs" href="#Introduction" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Introduction" aria-hidden="true">TOC</a></span></h2>
<p>This document aims in giving some quick references on a set of useful Git
commands. You should always use the extensive and detailed documentation
provided directly by Git:
</p>
<div class="example">
<pre class="example">git --help
man git
</pre></div>
<p>shows you the available subcommands,
</p>
<div class="example">
<pre class="example">git &lt;command&gt; --help
man git-&lt;command&gt;
</pre></div>
<p>shows information about the subcommand &lt;command&gt;.
</p>
<p>Additional information could be found on the
<a href="http://gitref.org">Git Reference</a> website.
</p>
<p>For more information about the Git project, visit the
<a href="http://git-scm.com/">Git website</a>.
</p>
<p>Consult these resources whenever you have problems, they are quite exhaustive.
</p>
<p>What follows now is a basic introduction to Git and some FFmpeg-specific
guidelines to ease the contribution to the project.
</p>
<a name="Basics-Usage"></a>
<h2 class="chapter">2 Basics Usage<span class="pull-right"><a class="anchor hidden-xs" href="#Basics-Usage" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Basics-Usage" aria-hidden="true">TOC</a></span></h2>
<a name="Get-Git"></a>
<h3 class="section">2.1 Get Git<span class="pull-right"><a class="anchor hidden-xs" href="#Get-Git" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Get-Git" aria-hidden="true">TOC</a></span></h3>
<p>You can get Git from <a href="http://git-scm.com/">http://git-scm.com/</a>
Most distribution and operating system provide a package for it.
</p>
<a name="Cloning-the-source-tree"></a>
<h3 class="section">2.2 Cloning the source tree<span class="pull-right"><a class="anchor hidden-xs" href="#Cloning-the-source-tree" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Cloning-the-source-tree" aria-hidden="true">TOC</a></span></h3>
<div class="example">
<pre class="example">git clone git://source.ffmpeg.org/ffmpeg &lt;target&gt;
</pre></div>
<p>This will put the FFmpeg sources into the directory <var>&lt;target&gt;</var>.
</p>
<div class="example">
<pre class="example">git clone git@source.ffmpeg.org:ffmpeg &lt;target&gt;
</pre></div>
<p>This will put the FFmpeg sources into the directory <var>&lt;target&gt;</var> and let
you push back your changes to the remote repository.
</p>
<div class="example">
<pre class="example">git clone gil@ffmpeg.org:ffmpeg-web &lt;target&gt;
</pre></div>
<p>This will put the source of the FFmpeg website into the directory
<var>&lt;target&gt;</var> and let you push back your changes to the remote repository.
(Note that <var>gil</var> stands for GItoLite and is not a typo of <var>git</var>.)
</p>
<p>If you don&rsquo;t have write-access to the ffmpeg-web repository, you can
create patches after making a read-only ffmpeg-web clone:
</p>
<div class="example">
<pre class="example">git clone git://ffmpeg.org/ffmpeg-web &lt;target&gt;
</pre></div>
<p>Make sure that you do not have Windows line endings in your checkouts,
otherwise you may experience spurious compilation failures. One way to
achieve this is to run
</p>
<div class="example">
<pre class="example">git config --global core.autocrlf false
</pre></div>
<span id="Updating-the-source-tree-to-the-latest-revision"></span><a name="Updating-the-source-tree-to-the-latest-revision-1"></a>
<h3 class="section">2.3 Updating the source tree to the latest revision<span class="pull-right"><a class="anchor hidden-xs" href="#Updating-the-source-tree-to-the-latest-revision-1" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Updating-the-source-tree-to-the-latest-revision-1" aria-hidden="true">TOC</a></span></h3>
<div class="example">
<pre class="example">git pull (--rebase)
</pre></div>
<p>pulls in the latest changes from the tracked branch. The tracked branch
can be remote. By default the master branch tracks the branch master in
the remote origin.
</p>
<div class="warning">
<p><code>--rebase</code> (see below) is recommended.
</p></div>
<a name="Rebasing-your-local-branches"></a>
<h3 class="section">2.4 Rebasing your local branches<span class="pull-right"><a class="anchor hidden-xs" href="#Rebasing-your-local-branches" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Rebasing-your-local-branches" aria-hidden="true">TOC</a></span></h3>
<div class="example">
<pre class="example">git pull --rebase
</pre></div>
<p>fetches the changes from the main repository and replays your local commits
over it. This is required to keep all your local changes at the top of
FFmpeg&rsquo;s master tree. The master tree will reject pushes with merge commits.
</p>
<a name="Adding_002fremoving-files_002fdirectories"></a>
<h3 class="section">2.5 Adding/removing files/directories<span class="pull-right"><a class="anchor hidden-xs" href="#Adding_002fremoving-files_002fdirectories" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Adding_002fremoving-files_002fdirectories" aria-hidden="true">TOC</a></span></h3>
<div class="example">
<pre class="example">git add [-A] &lt;filename/dirname&gt;
git rm [-r] &lt;filename/dirname&gt;
</pre></div>
<p>Git needs to get notified of all changes you make to your working
directory that makes files appear or disappear.
Line moves across files are automatically tracked.
</p>
<a name="Showing-modifications"></a>
<h3 class="section">2.6 Showing modifications<span class="pull-right"><a class="anchor hidden-xs" href="#Showing-modifications" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Showing-modifications" aria-hidden="true">TOC</a></span></h3>
<div class="example">
<pre class="example">git diff &lt;filename(s)&gt;
</pre></div>
<p>will show all local modifications in your working directory as unified diff.
</p>
<a name="Inspecting-the-changelog"></a>
<h3 class="section">2.7 Inspecting the changelog<span class="pull-right"><a class="anchor hidden-xs" href="#Inspecting-the-changelog" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Inspecting-the-changelog" aria-hidden="true">TOC</a></span></h3>
<div class="example">
<pre class="example">git log &lt;filename(s)&gt;
</pre></div>
<p>You may also use the graphical tools like <code>gitview</code> or <code>gitk</code>
or the web interface available at <a href="http://source.ffmpeg.org/">http://source.ffmpeg.org/</a>.
</p>
<a name="Checking-source-tree-status"></a>
<h3 class="section">2.8 Checking source tree status<span class="pull-right"><a class="anchor hidden-xs" href="#Checking-source-tree-status" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Checking-source-tree-status" aria-hidden="true">TOC</a></span></h3>
<div class="example">
<pre class="example">git status
</pre></div>
<p>detects all the changes you made and lists what actions will be taken in case
of a commit (additions, modifications, deletions, etc.).
</p>
<a name="Committing"></a>
<h3 class="section">2.9 Committing<span class="pull-right"><a class="anchor hidden-xs" href="#Committing" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Committing" aria-hidden="true">TOC</a></span></h3>
<div class="example">
<pre class="example">git diff --check
</pre></div>
<p>to double check your changes before committing them to avoid trouble later
on. All experienced developers do this on each and every commit, no matter
how small.
</p>
<p>Every one of them has been saved from looking like a fool by this many times.
It&rsquo;s very easy for stray debug output or cosmetic modifications to slip in,
please avoid problems through this extra level of scrutiny.
</p>
<p>For cosmetics-only commits you should get (almost) empty output from
</p>
<div class="example">
<pre class="example">git diff -w -b &lt;filename(s)&gt;
</pre></div>
<p>Also check the output of
</p>
<div class="example">
<pre class="example">git status
</pre></div>
<p>to make sure you don&rsquo;t have untracked files or deletions.
</p>
<div class="example">
<pre class="example">git add [-i|-p|-A] &lt;filenames/dirnames&gt;
</pre></div>
<p>Make sure you have told Git your name, email address and GPG key
</p>
<div class="example">
<pre class="example">git config --global user.name &quot;My Name&quot;
git config --global user.email my@email.invalid
git config --global user.signingkey ABCDEF0123245
</pre></div>
<p>Enable signing all commits or use -S
</p>
<div class="example">
<pre class="example">git config --global commit.gpgsign true
</pre></div>
<p>Use <samp>--global</samp> to set the global configuration for all your Git checkouts.
</p>
<p>Git will select the changes to the files for commit. Optionally you can use
the interactive or the patch mode to select hunk by hunk what should be
added to the commit.
</p>
<div class="example">
<pre class="example">git commit
</pre></div>
<p>Git will commit the selected changes to your current local branch.
</p>
<p>You will be prompted for a log message in an editor, which is either
set in your personal configuration file through
</p>
<div class="example">
<pre class="example">git config --global core.editor
</pre></div>
<p>or set by one of the following environment variables:
<var>GIT_EDITOR</var>, <var>VISUAL</var> or <var>EDITOR</var>.
</p>
<a name="Writing-a-commit-message"></a>
<h3 class="section">2.10 Writing a commit message<span class="pull-right"><a class="anchor hidden-xs" href="#Writing-a-commit-message" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Writing-a-commit-message" aria-hidden="true">TOC</a></span></h3>
<p>Log messages should be concise but descriptive.
</p>
<p>The first line must contain the context, a colon and a very short
summary of what the commit does. Details can be added, if necessary,
separated by an empty line. These details should not exceed 60-72 characters
per line, except when containing code.
</p>
<p>Example of a good commit message:
</p>
<div class="example">
<pre class="example">avcodec/cbs: add a helper to read extradata within packet side data
Using ff_cbs_read() on the raw buffer will not parse it as extradata,
resulting in parsing errors for example when handling ISOBMFF avcC.
This helper works around that.
</pre></div>
<div class="example">
<pre class="example">ptr might be NULL
</pre></div>
<p>If the summary on the first line is not enough, in the body of the message,
explain why you made a change, what you did will be obvious from the changes
themselves most of the time. Saying just &quot;bug fix&quot; or &quot;10l&quot; is bad. Remember
that people of varying skill levels look at and educate themselves while
reading through your code. Don&rsquo;t include filenames in log messages except in
the context, Git provides that information.
</p>
<p>If the commit fixes a registered issue, state it in a separate line of the
body: <code>Fix Trac ticket #42.</code>
</p>
<p>The first line will be used to name
the patch by <code>git format-patch</code>.
</p>
<p>Common mistakes for the first line, as seen in <code>git log --oneline</code>
include: missing context at the beginning; description of what the code did
before the patch; line too long or wrapped to the second line.
</p>
<a name="Preparing-a-patchset"></a>
<h3 class="section">2.11 Preparing a patchset<span class="pull-right"><a class="anchor hidden-xs" href="#Preparing-a-patchset" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Preparing-a-patchset" aria-hidden="true">TOC</a></span></h3>
<div class="example">
<pre class="example">git format-patch &lt;commit&gt; [-o directory]
</pre></div>
<p>will generate a set of patches for each commit between <var>&lt;commit&gt;</var> and
current <var>HEAD</var>. E.g.
</p>
<div class="example">
<pre class="example">git format-patch origin/master
</pre></div>
<p>will generate patches for all commits on current branch which are not
present in upstream.
A useful shortcut is also
</p>
<div class="example">
<pre class="example">git format-patch -n
</pre></div>
<p>which will generate patches from last <var>n</var> commits.
By default the patches are created in the current directory.
</p>
<a name="Sending-patches-for-review"></a>
<h3 class="section">2.12 Sending patches for review<span class="pull-right"><a class="anchor hidden-xs" href="#Sending-patches-for-review" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Sending-patches-for-review" aria-hidden="true">TOC</a></span></h3>
<div class="example">
<pre class="example">git send-email &lt;commit list|directory&gt;
</pre></div>
<p>will send the patches created by <code>git format-patch</code> or directly
generates them. All the email fields can be configured in the global/local
configuration or overridden by command line.
Note that this tool must often be installed separately (e.g. <var>git-email</var>
package on Debian-based distros).
</p>
<a name="Renaming_002fmoving_002fcopying-files-or-contents-of-files"></a>
<h3 class="section">2.13 Renaming/moving/copying files or contents of files<span class="pull-right"><a class="anchor hidden-xs" href="#Renaming_002fmoving_002fcopying-files-or-contents-of-files" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Renaming_002fmoving_002fcopying-files-or-contents-of-files" aria-hidden="true">TOC</a></span></h3>
<p>Git automatically tracks such changes, making those normal commits.
</p>
<div class="example">
<pre class="example">mv/cp path/file otherpath/otherfile
git add [-A] .
git commit
</pre></div>
<a name="Git-configuration"></a>
<h2 class="chapter">3 Git configuration<span class="pull-right"><a class="anchor hidden-xs" href="#Git-configuration" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Git-configuration" aria-hidden="true">TOC</a></span></h2>
<p>In order to simplify a few workflows, it is advisable to configure both
your personal Git installation and your local FFmpeg repository.
</p>
<a name="Personal-Git-installation"></a>
<h3 class="section">3.1 Personal Git installation<span class="pull-right"><a class="anchor hidden-xs" href="#Personal-Git-installation" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Personal-Git-installation" aria-hidden="true">TOC</a></span></h3>
<p>Add the following to your <samp>~/.gitconfig</samp> to help <code>git send-email</code>
and <code>git format-patch</code> detect renames:
</p>
<div class="example">
<pre class="example">[diff]
renames = copy
</pre></div>
<a name="Repository-configuration"></a>
<h3 class="section">3.2 Repository configuration<span class="pull-right"><a class="anchor hidden-xs" href="#Repository-configuration" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Repository-configuration" aria-hidden="true">TOC</a></span></h3>
<p>In order to have <code>git send-email</code> automatically send patches
to the ffmpeg-devel mailing list, add the following stanza
to <samp>/path/to/ffmpeg/repository/.git/config</samp>:
</p>
<div class="example">
<pre class="example">[sendemail]
to = ffmpeg-devel@ffmpeg.org
</pre></div>
<a name="FFmpeg-specific"></a>
<h2 class="chapter">4 FFmpeg specific<span class="pull-right"><a class="anchor hidden-xs" href="#FFmpeg-specific" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-FFmpeg-specific" aria-hidden="true">TOC</a></span></h2>
<a name="Reverting-broken-commits"></a>
<h3 class="section">4.1 Reverting broken commits<span class="pull-right"><a class="anchor hidden-xs" href="#Reverting-broken-commits" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Reverting-broken-commits" aria-hidden="true">TOC</a></span></h3>
<div class="example">
<pre class="example">git reset &lt;commit&gt;
</pre></div>
<p><code>git reset</code> will uncommit the changes till <var>&lt;commit&gt;</var> rewriting
the current branch history.
</p>
<div class="example">
<pre class="example">git commit --amend
</pre></div>
<p>allows one to amend the last commit details quickly.
</p>
<div class="example">
<pre class="example">git rebase -i origin/master
</pre></div>
<p>will replay local commits over the main repository allowing to edit, merge
or remove some of them in the process.
</p>
<div class="info">
<p><code>git reset</code>, <code>git commit --amend</code> and <code>git rebase</code>
rewrite history, so you should use them ONLY on your local or topic branches.
The main repository will reject those changes.
</p></div>
<div class="example">
<pre class="example">git revert &lt;commit&gt;
</pre></div>
<p><code>git revert</code> will generate a revert commit. This will not make the
faulty commit disappear from the history.
</p>
<a name="Pushing-changes-to-remote-trees"></a>
<h3 class="section">4.2 Pushing changes to remote trees<span class="pull-right"><a class="anchor hidden-xs" href="#Pushing-changes-to-remote-trees" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Pushing-changes-to-remote-trees" aria-hidden="true">TOC</a></span></h3>
<div class="example">
<pre class="example">git push origin master --dry-run
</pre></div>
<p>Will simulate a push of the local master branch to the default remote
(<var>origin</var>). And list which branches and ranges or commits would have been
pushed.
Git will prevent you from pushing changes if the local and remote trees are
out of sync. Refer to <a href="#Updating-the-source-tree-to-the-latest-revision">Updating the source tree to the latest revision</a>.
</p>
<div class="example">
<pre class="example">git remote add &lt;name&gt; &lt;url&gt;
</pre></div>
<p>Will add additional remote with a name reference, it is useful if you want
to push your local branch for review on a remote host.
</p>
<div class="example">
<pre class="example">git push &lt;remote&gt; &lt;refspec&gt;
</pre></div>
<p>Will push the changes to the <var>&lt;remote&gt;</var> repository.
Omitting <var>&lt;refspec&gt;</var> makes <code>git push</code> update all the remote
branches matching the local ones.
</p>
<a name="Finding-a-specific-svn-revision"></a>
<h3 class="section">4.3 Finding a specific svn revision<span class="pull-right"><a class="anchor hidden-xs" href="#Finding-a-specific-svn-revision" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Finding-a-specific-svn-revision" aria-hidden="true">TOC</a></span></h3>
<p>Since version 1.7.1 Git supports &lsquo;<samp>:/foo</samp>&rsquo; syntax for specifying commits
based on a regular expression. see man gitrevisions
</p>
<div class="example">
<pre class="example">git show :/'as revision 23456'
</pre></div>
<p>will show the svn changeset &lsquo;<samp>r23456</samp>&rsquo;. With older Git versions searching in
the <code>git log</code> output is the easiest option (especially if a pager with
search capabilities is used).
</p>
<p>This commit can be checked out with
</p>
<div class="example">
<pre class="example">git checkout -b svn_23456 :/'as revision 23456'
</pre></div>
<p>or for Git &lt; 1.7.1 with
</p>
<div class="example">
<pre class="example">git checkout -b svn_23456 $SHA1
</pre></div>
<p>where <var>$SHA1</var> is the commit hash from the <code>git log</code> output.
</p>
<a name="gpg-key-generation"></a>
<h2 class="chapter">5 gpg key generation<span class="pull-right"><a class="anchor hidden-xs" href="#gpg-key-generation" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-gpg-key-generation" aria-hidden="true">TOC</a></span></h2>
<p>If you have no gpg key yet, we recommend that you create a ed25519 based key as it
is small, fast and secure. Especially it results in small signatures in git.
</p>
<div class="example">
<pre class="example">gpg --default-new-key-algo &quot;ed25519/cert,sign+cv25519/encr&quot; --quick-generate-key &quot;human@server.com&quot;
</pre></div>
<p>When generating a key, make sure the email specified matches the email used in git as some sites like
github consider mismatches a reason to declare such commits unverified. After generating a key you
can add it to the MAINTAINER file and upload it to a keyserver.
</p>
<a name="Pre_002dpush-checklist"></a>
<h2 class="chapter">6 Pre-push checklist<span class="pull-right"><a class="anchor hidden-xs" href="#Pre_002dpush-checklist" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Pre_002dpush-checklist" aria-hidden="true">TOC</a></span></h2>
<p>Once you have a set of commits that you feel are ready for pushing,
work through the following checklist to doublecheck everything is in
proper order. This list tries to be exhaustive. In case you are just
pushing a typo in a comment, some of the steps may be unnecessary.
Apply your common sense, but if in doubt, err on the side of caution.
</p>
<p>First, make sure that the commits and branches you are going to push
match what you want pushed and that nothing is missing, extraneous or
wrong. You can see what will be pushed by running the git push command
with <samp>--dry-run</samp> first. And then inspecting the commits listed with
<code>git log -p 1234567..987654</code>. The <code>git status</code> command
may help in finding local changes that have been forgotten to be added.
</p>
<p>Next let the code pass through a full run of our test suite.
</p>
<ul>
<li> <code>make distclean</code>
</li><li> <code>/path/to/ffmpeg/configure</code>
</li><li> <code>make fate</code>
</li><li> if fate fails due to missing samples run <code>make fate-rsync</code> and retry
</li></ul>
<p>Make sure all your changes have been checked before pushing them, the
test suite only checks against regressions and that only to some extend. It does
obviously not check newly added features/code to be working unless you have
added a test for that (which is recommended).
</p>
<p>Also note that every single commit should pass the test suite, not just
the result of a series of patches.
</p>
<p>Once everything passed, push the changes to your public ffmpeg clone and post a
merge request to ffmpeg-devel. You can also push them directly but this is not
recommended.
</p>
<a name="Server-Issues"></a>
<h2 class="chapter">7 Server Issues<span class="pull-right"><a class="anchor hidden-xs" href="#Server-Issues" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Server-Issues" aria-hidden="true">TOC</a></span></h2>
<p>Contact the project admins at <a href="mailto:root@ffmpeg.org">root@ffmpeg.org</a> if you have technical
problems with the Git server.
</p> <p style="font-size: small;">
This document was generated using <a href="https://www.gnu.org/software/texinfo/"><em>makeinfo</em></a>.
</p>
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Libavcodec Documentation
</title>
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Libavcodec Documentation
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<li><a id="toc-See-Also" href="#See-Also">2 See Also</a></li>
<li><a id="toc-Authors" href="#Authors">3 Authors</a></li>
</ul>
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</div>
<a name="Description"></a>
<h2 class="chapter">1 Description<span class="pull-right"><a class="anchor hidden-xs" href="#Description" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Description" aria-hidden="true">TOC</a></span></h2>
<p>The libavcodec library provides a generic encoding/decoding framework
and contains multiple decoders and encoders for audio, video and
subtitle streams, and several bitstream filters.
</p>
<p>The shared architecture provides various services ranging from bit
stream I/O to DSP optimizations, and makes it suitable for
implementing robust and fast codecs as well as for experimentation.
</p>
<a name="See-Also"></a>
<h2 class="chapter">2 See Also<span class="pull-right"><a class="anchor hidden-xs" href="#See-Also" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-See-Also" aria-hidden="true">TOC</a></span></h2>
<p><a href="ffmpeg.html">ffmpeg</a>, <a href="ffplay.html">ffplay</a>, <a href="ffprobe.html">ffprobe</a>,
<a href="ffmpeg-codecs.html">ffmpeg-codecs</a>, <a href="ffmpeg-bitstream-filters.html">bitstream-filters</a>,
<a href="libavutil.html">libavutil</a>
</p>
<a name="Authors"></a>
<h2 class="chapter">3 Authors<span class="pull-right"><a class="anchor hidden-xs" href="#Authors" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Authors" aria-hidden="true">TOC</a></span></h2>
<p>The FFmpeg developers.
</p>
<p>For details about the authorship, see the Git history of the project
(git://source.ffmpeg.org/ffmpeg), e.g. by typing the command
<code>git log</code> in the FFmpeg source directory, or browsing the
online repository at <a href="http://source.ffmpeg.org">http://source.ffmpeg.org</a>.
</p>
<p>Maintainers for the specific components are listed in the file
<samp>MAINTAINERS</samp> in the source code tree.
</p>
<p style="font-size: small;">
This document was generated using <a href="https://www.gnu.org/software/texinfo/"><em>makeinfo</em></a>.
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Libavdevice Documentation
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Libavdevice Documentation
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<div class="contents">
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<li><a id="toc-Authors" href="#Authors">3 Authors</a></li>
</ul>
</div>
</div>
<a name="Description"></a>
<h2 class="chapter">1 Description<span class="pull-right"><a class="anchor hidden-xs" href="#Description" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Description" aria-hidden="true">TOC</a></span></h2>
<p>The libavdevice library provides a generic framework for grabbing from
and rendering to many common multimedia input/output devices, and
supports several input and output devices, including Video4Linux2,
VfW, DShow, and ALSA.
</p>
<a name="See-Also"></a>
<h2 class="chapter">2 See Also<span class="pull-right"><a class="anchor hidden-xs" href="#See-Also" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-See-Also" aria-hidden="true">TOC</a></span></h2>
<p><a href="ffmpeg.html">ffmpeg</a>, <a href="ffplay.html">ffplay</a>, <a href="ffprobe.html">ffprobe</a>,
<a href="ffmpeg-devices.html">ffmpeg-devices</a>,
<a href="libavutil.html">libavutil</a>, <a href="libavcodec.html">libavcodec</a>, <a href="libavformat.html">libavformat</a>
</p>
<a name="Authors"></a>
<h2 class="chapter">3 Authors<span class="pull-right"><a class="anchor hidden-xs" href="#Authors" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Authors" aria-hidden="true">TOC</a></span></h2>
<p>The FFmpeg developers.
</p>
<p>For details about the authorship, see the Git history of the project
(git://source.ffmpeg.org/ffmpeg), e.g. by typing the command
<code>git log</code> in the FFmpeg source directory, or browsing the
online repository at <a href="http://source.ffmpeg.org">http://source.ffmpeg.org</a>.
</p>
<p>Maintainers for the specific components are listed in the file
<samp>MAINTAINERS</samp> in the source code tree.
</p>
<p style="font-size: small;">
This document was generated using <a href="https://www.gnu.org/software/texinfo/"><em>makeinfo</em></a>.
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Libavfilter Documentation
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Libavfilter Documentation
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<div class="contents">
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<li><a id="toc-Authors" href="#Authors">3 Authors</a></li>
</ul>
</div>
</div>
<a name="Description"></a>
<h2 class="chapter">1 Description<span class="pull-right"><a class="anchor hidden-xs" href="#Description" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Description" aria-hidden="true">TOC</a></span></h2>
<p>The libavfilter library provides a generic audio/video filtering
framework containing several filters, sources and sinks.
</p>
<a name="See-Also"></a>
<h2 class="chapter">2 See Also<span class="pull-right"><a class="anchor hidden-xs" href="#See-Also" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-See-Also" aria-hidden="true">TOC</a></span></h2>
<p><a href="ffmpeg.html">ffmpeg</a>, <a href="ffplay.html">ffplay</a>, <a href="ffprobe.html">ffprobe</a>,
<a href="ffmpeg-filters.html">ffmpeg-filters</a>,
<a href="libavutil.html">libavutil</a>, <a href="libswscale.html">libswscale</a>, <a href="libswresample.html">libswresample</a>,
<a href="libavcodec.html">libavcodec</a>, <a href="libavformat.html">libavformat</a>, <a href="libavdevice.html">libavdevice</a>
</p>
<a name="Authors"></a>
<h2 class="chapter">3 Authors<span class="pull-right"><a class="anchor hidden-xs" href="#Authors" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Authors" aria-hidden="true">TOC</a></span></h2>
<p>The FFmpeg developers.
</p>
<p>For details about the authorship, see the Git history of the project
(git://source.ffmpeg.org/ffmpeg), e.g. by typing the command
<code>git log</code> in the FFmpeg source directory, or browsing the
online repository at <a href="http://source.ffmpeg.org">http://source.ffmpeg.org</a>.
</p>
<p>Maintainers for the specific components are listed in the file
<samp>MAINTAINERS</samp> in the source code tree.
</p>
<p style="font-size: small;">
This document was generated using <a href="https://www.gnu.org/software/texinfo/"><em>makeinfo</em></a>.
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Libavformat Documentation
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Libavformat Documentation
</h1>
<div align="center">
</div>
<a name="SEC_Top"></a>
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<div class="contents">
<ul class="no-bullet">
<li><a id="toc-Description" href="#Description">1 Description</a></li>
<li><a id="toc-See-Also" href="#See-Also">2 See Also</a></li>
<li><a id="toc-Authors" href="#Authors">3 Authors</a></li>
</ul>
</div>
</div>
<a name="Description"></a>
<h2 class="chapter">1 Description<span class="pull-right"><a class="anchor hidden-xs" href="#Description" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Description" aria-hidden="true">TOC</a></span></h2>
<p>The libavformat library provides a generic framework for multiplexing
and demultiplexing (muxing and demuxing) audio, video and subtitle
streams. It encompasses multiple muxers and demuxers for multimedia
container formats.
</p>
<p>It also supports several input and output protocols to access a media
resource.
</p>
<a name="See-Also"></a>
<h2 class="chapter">2 See Also<span class="pull-right"><a class="anchor hidden-xs" href="#See-Also" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-See-Also" aria-hidden="true">TOC</a></span></h2>
<p><a href="ffmpeg.html">ffmpeg</a>, <a href="ffplay.html">ffplay</a>, <a href="ffprobe.html">ffprobe</a>,
<a href="ffmpeg-formats.html">ffmpeg-formats</a>, <a href="ffmpeg-protocols.html">ffmpeg-protocols</a>,
<a href="libavutil.html">libavutil</a>, <a href="libavcodec.html">libavcodec</a>
</p>
<a name="Authors"></a>
<h2 class="chapter">3 Authors<span class="pull-right"><a class="anchor hidden-xs" href="#Authors" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Authors" aria-hidden="true">TOC</a></span></h2>
<p>The FFmpeg developers.
</p>
<p>For details about the authorship, see the Git history of the project
(git://source.ffmpeg.org/ffmpeg), e.g. by typing the command
<code>git log</code> in the FFmpeg source directory, or browsing the
online repository at <a href="http://source.ffmpeg.org">http://source.ffmpeg.org</a>.
</p>
<p>Maintainers for the specific components are listed in the file
<samp>MAINTAINERS</samp> in the source code tree.
</p>
<p style="font-size: small;">
This document was generated using <a href="https://www.gnu.org/software/texinfo/"><em>makeinfo</em></a>.
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</ul>
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</div>
<a name="Description"></a>
<h2 class="chapter">1 Description<span class="pull-right"><a class="anchor hidden-xs" href="#Description" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Description" aria-hidden="true">TOC</a></span></h2>
<p>The libavutil library is a utility library to aid portable
multimedia programming. It contains safe portable string functions,
random number generators, data structures, additional mathematics
functions, cryptography and multimedia related functionality (like
enumerations for pixel and sample formats). It is not a library for
code needed by both libavcodec and libavformat.
</p>
<p>The goals for this library is to be:
</p>
<dl compact="compact">
<dt><span><strong>Modular</strong></span></dt>
<dd><p>It should have few interdependencies and the possibility of disabling individual
parts during <code>./configure</code>.
</p>
</dd>
<dt><span><strong>Small</strong></span></dt>
<dd><p>Both sources and objects should be small.
</p>
</dd>
<dt><span><strong>Efficient</strong></span></dt>
<dd><p>It should have low CPU and memory usage.
</p>
</dd>
<dt><span><strong>Useful</strong></span></dt>
<dd><p>It should avoid useless features that almost no one needs.
</p></dd>
</dl>
<a name="See-Also"></a>
<h2 class="chapter">2 See Also<span class="pull-right"><a class="anchor hidden-xs" href="#See-Also" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-See-Also" aria-hidden="true">TOC</a></span></h2>
<p><a href="ffmpeg.html">ffmpeg</a>, <a href="ffplay.html">ffplay</a>, <a href="ffprobe.html">ffprobe</a>,
<a href="ffmpeg-utils.html">ffmpeg-utils</a>
</p>
<a name="Authors"></a>
<h2 class="chapter">3 Authors<span class="pull-right"><a class="anchor hidden-xs" href="#Authors" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Authors" aria-hidden="true">TOC</a></span></h2>
<p>The FFmpeg developers.
</p>
<p>For details about the authorship, see the Git history of the project
(git://source.ffmpeg.org/ffmpeg), e.g. by typing the command
<code>git log</code> in the FFmpeg source directory, or browsing the
online repository at <a href="http://source.ffmpeg.org">http://source.ffmpeg.org</a>.
</p>
<p>Maintainers for the specific components are listed in the file
<samp>MAINTAINERS</samp> in the source code tree.
</p>
<p style="font-size: small;">
This document was generated using <a href="https://www.gnu.org/software/texinfo/"><em>makeinfo</em></a>.
</p>
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<title>
Libswresample Documentation
</title>
<meta name="viewport" content="width=device-width,initial-scale=1.0">
<link rel="stylesheet" type="text/css" href="bootstrap.min.css">
<link rel="stylesheet" type="text/css" href="style.min.css">
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<h1>
Libswresample Documentation
</h1>
<div align="center">
</div>
<a name="SEC_Top"></a>
<div class="Contents_element" id="SEC_Contents">
<h2 class="contents-heading">Table of Contents</h2>
<div class="contents">
<ul class="no-bullet">
<li><a id="toc-Description" href="#Description">1 Description</a></li>
<li><a id="toc-See-Also" href="#See-Also">2 See Also</a></li>
<li><a id="toc-Authors" href="#Authors">3 Authors</a></li>
</ul>
</div>
</div>
<a name="Description"></a>
<h2 class="chapter">1 Description<span class="pull-right"><a class="anchor hidden-xs" href="#Description" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Description" aria-hidden="true">TOC</a></span></h2>
<p>The libswresample library performs highly optimized audio resampling,
rematrixing and sample format conversion operations.
</p>
<p>Specifically, this library performs the following conversions:
</p>
<ul>
<li> <em>Resampling</em>: is the process of changing the audio rate, for
example from a high sample rate of 44100Hz to 8000Hz. Audio
conversion from high to low sample rate is a lossy process. Several
resampling options and algorithms are available.
</li><li> <em>Format conversion</em>: is the process of converting the type of
samples, for example from 16-bit signed samples to unsigned 8-bit or
float samples. It also handles packing conversion, when passing from
packed layout (all samples belonging to distinct channels interleaved
in the same buffer), to planar layout (all samples belonging to the
same channel stored in a dedicated buffer or &quot;plane&quot;).
</li><li> <em>Rematrixing</em>: is the process of changing the channel layout, for
example from stereo to mono. When the input channels cannot be mapped
to the output streams, the process is lossy, since it involves
different gain factors and mixing.
</li></ul>
<p>Various other audio conversions (e.g. stretching and padding) are
enabled through dedicated options.
</p>
<a name="See-Also"></a>
<h2 class="chapter">2 See Also<span class="pull-right"><a class="anchor hidden-xs" href="#See-Also" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-See-Also" aria-hidden="true">TOC</a></span></h2>
<p><a href="ffmpeg.html">ffmpeg</a>, <a href="ffplay.html">ffplay</a>, <a href="ffprobe.html">ffprobe</a>,
<a href="ffmpeg-resampler.html">ffmpeg-resampler</a>,
<a href="libavutil.html">libavutil</a>
</p>
<a name="Authors"></a>
<h2 class="chapter">3 Authors<span class="pull-right"><a class="anchor hidden-xs" href="#Authors" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Authors" aria-hidden="true">TOC</a></span></h2>
<p>The FFmpeg developers.
</p>
<p>For details about the authorship, see the Git history of the project
(git://source.ffmpeg.org/ffmpeg), e.g. by typing the command
<code>git log</code> in the FFmpeg source directory, or browsing the
online repository at <a href="http://source.ffmpeg.org">http://source.ffmpeg.org</a>.
</p>
<p>Maintainers for the specific components are listed in the file
<samp>MAINTAINERS</samp> in the source code tree.
</p>
<p style="font-size: small;">
This document was generated using <a href="https://www.gnu.org/software/texinfo/"><em>makeinfo</em></a>.
</p>
</div>
</body>
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<meta charset="utf-8">
<title>
Libswscale Documentation
</title>
<meta name="viewport" content="width=device-width,initial-scale=1.0">
<link rel="stylesheet" type="text/css" href="bootstrap.min.css">
<link rel="stylesheet" type="text/css" href="style.min.css">
</head>
<body>
<div class="container">
<h1>
Libswscale Documentation
</h1>
<div align="center">
</div>
<a name="SEC_Top"></a>
<div class="Contents_element" id="SEC_Contents">
<h2 class="contents-heading">Table of Contents</h2>
<div class="contents">
<ul class="no-bullet">
<li><a id="toc-Description" href="#Description">1 Description</a></li>
<li><a id="toc-See-Also" href="#See-Also">2 See Also</a></li>
<li><a id="toc-Authors" href="#Authors">3 Authors</a></li>
</ul>
</div>
</div>
<a name="Description"></a>
<h2 class="chapter">1 Description<span class="pull-right"><a class="anchor hidden-xs" href="#Description" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Description" aria-hidden="true">TOC</a></span></h2>
<p>The libswscale library performs highly optimized image scaling and
colorspace and pixel format conversion operations.
</p>
<p>Specifically, this library performs the following conversions:
</p>
<ul>
<li> <em>Rescaling</em>: is the process of changing the video size. Several
rescaling options and algorithms are available. This is usually a
lossy process.
</li><li> <em>Pixel format conversion</em>: is the process of converting the image
format and colorspace of the image, for example from planar YUV420P to
RGB24 packed. It also handles packing conversion, that is converts
from packed layout (all pixels belonging to distinct planes
interleaved in the same buffer), to planar layout (all samples
belonging to the same plane stored in a dedicated buffer or &quot;plane&quot;).
<p>This is usually a lossy process in case the source and destination
colorspaces differ.
</p></li></ul>
<a name="See-Also"></a>
<h2 class="chapter">2 See Also<span class="pull-right"><a class="anchor hidden-xs" href="#See-Also" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-See-Also" aria-hidden="true">TOC</a></span></h2>
<p><a href="ffmpeg.html">ffmpeg</a>, <a href="ffplay.html">ffplay</a>, <a href="ffprobe.html">ffprobe</a>,
<a href="ffmpeg-scaler.html">ffmpeg-scaler</a>,
<a href="libavutil.html">libavutil</a>
</p>
<a name="Authors"></a>
<h2 class="chapter">3 Authors<span class="pull-right"><a class="anchor hidden-xs" href="#Authors" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Authors" aria-hidden="true">TOC</a></span></h2>
<p>The FFmpeg developers.
</p>
<p>For details about the authorship, see the Git history of the project
(git://source.ffmpeg.org/ffmpeg), e.g. by typing the command
<code>git log</code> in the FFmpeg source directory, or browsing the
online repository at <a href="http://source.ffmpeg.org">http://source.ffmpeg.org</a>.
</p>
<p>Maintainers for the specific components are listed in the file
<samp>MAINTAINERS</samp> in the source code tree.
</p>
<p style="font-size: small;">
This document was generated using <a href="https://www.gnu.org/software/texinfo/"><em>makeinfo</em></a>.
</p>
</div>
</body>
</html>

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<meta charset="utf-8">
<title>
FFmpeg Mailing List FAQ
</title>
<meta name="viewport" content="width=device-width,initial-scale=1.0">
<link rel="stylesheet" type="text/css" href="bootstrap.min.css">
<link rel="stylesheet" type="text/css" href="style.min.css">
</head>
<body>
<div class="container">
<h1>
FFmpeg Mailing List FAQ
</h1>
<div align="center">
</div>
<a name="SEC_Top"></a>
<div class="Contents_element" id="SEC_Contents">
<h2 class="contents-heading">Table of Contents</h2>
<div class="contents">
<ul class="no-bullet">
<li><a id="toc-General-Questions" href="#General-Questions">1 General Questions</a>
<ul class="no-bullet">
<li><a id="toc-What-is-a-mailing-list_003f" href="#What-is-a-mailing-list_003f">1.1 What is a mailing list?</a></li>
<li><a id="toc-What-type-of-questions-can-I-ask_003f" href="#What-type-of-questions-can-I-ask_003f">1.2 What type of questions can I ask?</a></li>
<li><a id="toc-How-do-I-ask-a-question-or-send-a-message-to-a-mailing-list_003f-1" href="#How-do-I-ask-a-question-or-send-a-message-to-a-mailing-list_003f-1">1.3 How do I ask a question or send a message to a mailing list?</a></li>
</ul></li>
<li><a id="toc-Subscribing-_002f-Unsubscribing" href="#Subscribing-_002f-Unsubscribing">2 Subscribing / Unsubscribing</a>
<ul class="no-bullet">
<li><a id="toc-How-do-I-subscribe_003f-1" href="#How-do-I-subscribe_003f-1">2.1 How do I subscribe?</a></li>
<li><a id="toc-How-do-I-unsubscribe_003f" href="#How-do-I-unsubscribe_003f">2.2 How do I unsubscribe?</a></li>
</ul></li>
<li><a id="toc-Moderation-Queue" href="#Moderation-Queue">3 Moderation Queue</a>
<ul class="no-bullet">
<li><a id="toc-Why-is-my-message-awaiting-moderator-approval_003f-1" href="#Why-is-my-message-awaiting-moderator-approval_003f-1">3.1 Why is my message awaiting moderator approval?</a></li>
<li><a id="toc-How-long-does-it-take-for-my-message-in-the-moderation-queue-to-be-approved_003f" href="#How-long-does-it-take-for-my-message-in-the-moderation-queue-to-be-approved_003f">3.2 How long does it take for my message in the moderation queue to be approved?</a></li>
<li><a id="toc-How-do-I-delete-my-message-in-the-moderation-queue_003f-1" href="#How-do-I-delete-my-message-in-the-moderation-queue_003f-1">3.3 How do I delete my message in the moderation queue?</a></li>
</ul></li>
<li><a id="toc-Archives" href="#Archives">4 Archives</a>
<ul class="no-bullet">
<li><a id="toc-Where-are-the-archives_003f-1" href="#Where-are-the-archives_003f-1">4.1 Where are the archives?</a></li>
<li><a id="toc-How-do-I-reply-to-a-message-in-the-archives_003f" href="#How-do-I-reply-to-a-message-in-the-archives_003f">4.2 How do I reply to a message in the archives?</a></li>
<li><a id="toc-How-do-I-search-the-archives_003f" href="#How-do-I-search-the-archives_003f">4.3 How do I search the archives?</a></li>
</ul></li>
<li><a id="toc-Other" href="#Other">5 Other</a>
<ul class="no-bullet">
<li><a id="toc-Is-there-an-alternative-to-the-mailing-list_003f" href="#Is-there-an-alternative-to-the-mailing-list_003f">5.1 Is there an alternative to the mailing list?</a></li>
<li><a id="toc-What-is-top_002dposting_003f-1" href="#What-is-top_002dposting_003f-1">5.2 What is top-posting?</a></li>
<li><a id="toc-What-is-the-message-size-limit_003f-1" href="#What-is-the-message-size-limit_003f-1">5.3 What is the message size limit?</a></li>
<li><a id="toc-Where-can-I-upload-sample-files_003f" href="#Where-can-I-upload-sample-files_003f">5.4 Where can I upload sample files?</a></li>
<li><a id="toc-Will-I-receive-spam-if-I-send-and_002for-subscribe-to-a-mailing-list_003f" href="#Will-I-receive-spam-if-I-send-and_002for-subscribe-to-a-mailing-list_003f">5.5 Will I receive spam if I send and/or subscribe to a mailing list?</a></li>
<li><a id="toc-How-do-I-filter-mailing-list-messages_003f" href="#How-do-I-filter-mailing-list-messages_003f">5.6 How do I filter mailing list messages?</a></li>
<li><a id="toc-How-do-I-disable-mail-delivery-without-unsubscribing_003f-1" href="#How-do-I-disable-mail-delivery-without-unsubscribing_003f-1">5.7 How do I disable mail delivery without unsubscribing?</a></li>
<li><a id="toc-Why-is-the-mailing-list-munging-my-address_003f-1" href="#Why-is-the-mailing-list-munging-my-address_003f-1">5.8 Why is the mailing list munging my address?</a></li>
</ul></li>
<li><a id="toc-Rules-and-Etiquette" href="#Rules-and-Etiquette">6 Rules and Etiquette</a>
<ul class="no-bullet">
<li><a id="toc-What-are-the-rules-and-the-proper-etiquette_003f" href="#What-are-the-rules-and-the-proper-etiquette_003f">6.1 What are the rules and the proper etiquette?</a></li>
</ul></li>
<li><a id="toc-Help" href="#Help">7 Help</a>
<ul class="no-bullet">
<li><a id="toc-Why-am-I-not-receiving-any-messages_003f" href="#Why-am-I-not-receiving-any-messages_003f">7.1 Why am I not receiving any messages?</a></li>
<li><a id="toc-Why-are-my-sent-messages-not-showing-up_003f" href="#Why-are-my-sent-messages-not-showing-up_003f">7.2 Why are my sent messages not showing up?</a></li>
<li><a id="toc-Why-do-I-keep-getting-unsubscribed-from-ffmpeg_002ddevel_003f-1" href="#Why-do-I-keep-getting-unsubscribed-from-ffmpeg_002ddevel_003f-1">7.3 Why do I keep getting unsubscribed from ffmpeg-devel?</a></li>
<li><a id="toc-Who-do-I-contact-if-I-have-a-problem-with-the-mailing-list_003f-1" href="#Who-do-I-contact-if-I-have-a-problem-with-the-mailing-list_003f-1">7.4 Who do I contact if I have a problem with the mailing list?</a></li>
</ul></li>
</ul>
</div>
</div>
<a name="General-Questions"></a>
<h2 class="chapter">1 General Questions<span class="pull-right"><a class="anchor hidden-xs" href="#General-Questions" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-General-Questions" aria-hidden="true">TOC</a></span></h2>
<a name="What-is-a-mailing-list_003f"></a>
<h3 class="section">1.1 What is a mailing list?<span class="pull-right"><a class="anchor hidden-xs" href="#What-is-a-mailing-list_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-What-is-a-mailing-list_003f" aria-hidden="true">TOC</a></span></h3>
<p>A mailing list is not much different than emailing someone, but the
main difference is that your message is received by everyone who
subscribes to the list. It is somewhat like a forum but in email form.
</p>
<p>See the <a href="https://lists.ffmpeg.org/pipermail/ffmpeg-user/">ffmpeg-user archives</a>
for examples.
</p>
<a name="What-type-of-questions-can-I-ask_003f"></a>
<h3 class="section">1.2 What type of questions can I ask?<span class="pull-right"><a class="anchor hidden-xs" href="#What-type-of-questions-can-I-ask_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-What-type-of-questions-can-I-ask_003f" aria-hidden="true">TOC</a></span></h3>
<ul>
<li> <a href="https://lists.ffmpeg.org/mailman/listinfo/ffmpeg-user/">ffmpeg-user</a>:
For questions involving unscripted usage or compilation of the FFmpeg
command-line tools (<code>ffmpeg</code>, <code>ffprobe</code>, <code>ffplay</code>).
</li><li> <a href="https://lists.ffmpeg.org/mailman/listinfo/libav-user/">libav-user</a>:
For questions involving the FFmpeg libav* libraries (libavcodec,
libavformat, libavfilter, etc).
</li><li> <a href="https://lists.ffmpeg.org/mailman/listinfo/ffmpeg-devel/">ffmpeg-devel</a>:
For discussions involving the development of FFmpeg and for submitting
patches. User questions should be asked at ffmpeg-user or libav-user.
</li></ul>
<p>To report a bug see <a href="https://ffmpeg.org/bugreports.html">https://ffmpeg.org/bugreports.html</a>.
</p>
<p>We cannot provide help for scripts and/or third-party tools.
</p>
<span id="How-do-I-ask-a-question-or-send-a-message-to-a-mailing-list_003f"></span><a name="How-do-I-ask-a-question-or-send-a-message-to-a-mailing-list_003f-1"></a>
<h3 class="section">1.3 How do I ask a question or send a message to a mailing list?<span class="pull-right"><a class="anchor hidden-xs" href="#How-do-I-ask-a-question-or-send-a-message-to-a-mailing-list_003f-1" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-How-do-I-ask-a-question-or-send-a-message-to-a-mailing-list_003f-1" aria-hidden="true">TOC</a></span></h3>
<p>First you must <a href="#How-do-I-subscribe_003f">subscribe</a>. Then all you have to do is
send an email:
</p>
<ul>
<li> Email <a href="mailto:ffmpeg-user@ffmpeg.org">ffmpeg-user@ffmpeg.org</a> to send a message to the
ffmpeg-user mailing list.
</li><li> Email <a href="mailto:libav-user@ffmpeg.org">libav-user@ffmpeg.org</a> to send a message to the
libav-user mailing list.
</li><li> Email <a href="mailto:ffmpeg-devel@ffmpeg.org">ffmpeg-devel@ffmpeg.org</a> to send a message to the
ffmpeg-devel mailing list.
</li></ul>
<a name="Subscribing-_002f-Unsubscribing"></a>
<h2 class="chapter">2 Subscribing / Unsubscribing<span class="pull-right"><a class="anchor hidden-xs" href="#Subscribing-_002f-Unsubscribing" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Subscribing-_002f-Unsubscribing" aria-hidden="true">TOC</a></span></h2>
<span id="How-do-I-subscribe_003f"></span><a name="How-do-I-subscribe_003f-1"></a>
<h3 class="section">2.1 How do I subscribe?<span class="pull-right"><a class="anchor hidden-xs" href="#How-do-I-subscribe_003f-1" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-How-do-I-subscribe_003f-1" aria-hidden="true">TOC</a></span></h3>
<p>Email <a href="mailto:ffmpeg-user-request@ffmpeg.org">ffmpeg-user-request@ffmpeg.org</a> with the subject
<em>subscribe</em>.
</p>
<p>Or visit the <a href="https://lists.ffmpeg.org/mailman/listinfo/ffmpeg-user/">ffmpeg-user mailing list info page</a>
and refer to the <em>Subscribing to ffmpeg-user</em> section.
</p>
<p>The process is the same for the other mailing lists.
</p>
<a name="How-do-I-unsubscribe_003f"></a>
<h3 class="section">2.2 How do I unsubscribe?<span class="pull-right"><a class="anchor hidden-xs" href="#How-do-I-unsubscribe_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-How-do-I-unsubscribe_003f" aria-hidden="true">TOC</a></span></h3>
<p>Email <a href="mailto:ffmpeg-user-request@ffmpeg.org">ffmpeg-user-request@ffmpeg.org</a> with subject <em>unsubscribe</em>.
</p>
<p>Or visit the <a href="https://lists.ffmpeg.org/mailman/listinfo/ffmpeg-user/">ffmpeg-user mailing list info page</a>,
scroll to bottom of page, enter your email address in the box, and click
the <em>Unsubscribe or edit options</em> button.
</p>
<p>The process is the same for the other mailing lists.
</p>
<p>Please avoid asking a mailing list admin to unsubscribe you unless you
are absolutely unable to do so by yourself. See <a href="#Who-do-I-contact-if-I-have-a-problem-with-the-mailing-list_003f">Who do I contact if I have a problem with the mailing list?</a>
</p>
<p>Note that it is possible to temporarily halt message delivery (vacation mode).
See <a href="#How-do-I-disable-mail-delivery-without-unsubscribing_003f">How do I disable mail delivery without unsubscribing?</a>
</p>
<a name="Moderation-Queue"></a>
<h2 class="chapter">3 Moderation Queue<span class="pull-right"><a class="anchor hidden-xs" href="#Moderation-Queue" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Moderation-Queue" aria-hidden="true">TOC</a></span></h2>
<span id="Why-is-my-message-awaiting-moderator-approval_003f"></span><a name="Why-is-my-message-awaiting-moderator-approval_003f-1"></a>
<h3 class="section">3.1 Why is my message awaiting moderator approval?<span class="pull-right"><a class="anchor hidden-xs" href="#Why-is-my-message-awaiting-moderator-approval_003f-1" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Why-is-my-message-awaiting-moderator-approval_003f-1" aria-hidden="true">TOC</a></span></h3>
<p>Some messages are automatically held in the <em>moderation queue</em> and
must be manually approved by a mailing list admin:
</p>
<p>These are:
</p>
<ul>
<li> Messages that exceed the <a href="#What-is-the-message-size-limit_003f">message size limit</a>.
</li><li> Messages from users whose accounts have been set with the <em>moderation flag</em>
(very rarely occurs, but may if a user repeatedly ignores the rules
or is abusive towards others).
</li></ul>
<a name="How-long-does-it-take-for-my-message-in-the-moderation-queue-to-be-approved_003f"></a>
<h3 class="section">3.2 How long does it take for my message in the moderation queue to be approved?<span class="pull-right"><a class="anchor hidden-xs" href="#How-long-does-it-take-for-my-message-in-the-moderation-queue-to-be-approved_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-How-long-does-it-take-for-my-message-in-the-moderation-queue-to-be-approved_003f" aria-hidden="true">TOC</a></span></h3>
<p>The queue is not checked on a regular basis. You can ask on the
<tt>#ffmpeg-devel</tt> IRC channel on Libera Chat for someone to approve your message.
</p>
<span id="How-do-I-delete-my-message-in-the-moderation-queue_003f"></span><a name="How-do-I-delete-my-message-in-the-moderation-queue_003f-1"></a>
<h3 class="section">3.3 How do I delete my message in the moderation queue?<span class="pull-right"><a class="anchor hidden-xs" href="#How-do-I-delete-my-message-in-the-moderation-queue_003f-1" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-How-do-I-delete-my-message-in-the-moderation-queue_003f-1" aria-hidden="true">TOC</a></span></h3>
<p>You should have received an email with the subject <em>Your message to &lt;mailing list name&gt; awaits moderator approval</em>.
A link is in the message that will allow you to delete your message
unless a mailing list admin already approved or rejected it.
</p>
<a name="Archives"></a>
<h2 class="chapter">4 Archives<span class="pull-right"><a class="anchor hidden-xs" href="#Archives" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Archives" aria-hidden="true">TOC</a></span></h2>
<span id="Where-are-the-archives_003f"></span><a name="Where-are-the-archives_003f-1"></a>
<h3 class="section">4.1 Where are the archives?<span class="pull-right"><a class="anchor hidden-xs" href="#Where-are-the-archives_003f-1" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Where-are-the-archives_003f-1" aria-hidden="true">TOC</a></span></h3>
<p>See the <em>Archives</em> section on the <a href="https://ffmpeg.org/contact.html">FFmpeg Contact</a>
page for links to all FFmpeg mailing list archives.
</p>
<p>Note that the archives are split by month. Discussions that span
several months will be split into separate months in the archives.
</p>
<a name="How-do-I-reply-to-a-message-in-the-archives_003f"></a>
<h3 class="section">4.2 How do I reply to a message in the archives?<span class="pull-right"><a class="anchor hidden-xs" href="#How-do-I-reply-to-a-message-in-the-archives_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-How-do-I-reply-to-a-message-in-the-archives_003f" aria-hidden="true">TOC</a></span></h3>
<p>Click the email link at the top of the message just under the subject
title. The link will provide the proper headers to keep the message
within the thread.
</p>
<p>Note that you must be subscribed to send a message to the ffmpeg-user or
libav-user mailing lists.
</p>
<a name="How-do-I-search-the-archives_003f"></a>
<h3 class="section">4.3 How do I search the archives?<span class="pull-right"><a class="anchor hidden-xs" href="#How-do-I-search-the-archives_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-How-do-I-search-the-archives_003f" aria-hidden="true">TOC</a></span></h3>
<p>Perform a site search using your favorite search engine. Example:
</p>
<p><tt>site:lists.ffmpeg.org/pipermail/ffmpeg-user/ &quot;search term&quot;</tt>
</p>
<a name="Other"></a>
<h2 class="chapter">5 Other<span class="pull-right"><a class="anchor hidden-xs" href="#Other" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Other" aria-hidden="true">TOC</a></span></h2>
<a name="Is-there-an-alternative-to-the-mailing-list_003f"></a>
<h3 class="section">5.1 Is there an alternative to the mailing list?<span class="pull-right"><a class="anchor hidden-xs" href="#Is-there-an-alternative-to-the-mailing-list_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Is-there-an-alternative-to-the-mailing-list_003f" aria-hidden="true">TOC</a></span></h3>
<p>You can ask for help in the official <tt>#ffmpeg</tt> IRC channel on Libera Chat.
</p>
<p>Some users prefer the third-party <a href="http://www.ffmpeg-archive.org/">Nabble</a>
interface which presents the mailing lists in a typical forum layout.
</p>
<p>There are also numerous third-party help sites such as
<a href="https://superuser.com/tags/ffmpeg">Super User</a> and
<a href="https://www.reddit.com/r/ffmpeg/">r/ffmpeg on reddit</a>.
</p>
<span id="What-is-top_002dposting_003f"></span><a name="What-is-top_002dposting_003f-1"></a>
<h3 class="section">5.2 What is top-posting?<span class="pull-right"><a class="anchor hidden-xs" href="#What-is-top_002dposting_003f-1" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-What-is-top_002dposting_003f-1" aria-hidden="true">TOC</a></span></h3>
<p>See <a href="https://en.wikipedia.org/wiki/Posting_style#Top-posting">https://en.wikipedia.org/wiki/Posting_style#Top-posting</a>.
</p>
<p>Instead, use trimmed interleaved/inline replies (<a href="https://lists.ffmpeg.org/pipermail/ffmpeg-user/2017-April/035849.html">example</a>).
</p>
<span id="What-is-the-message-size-limit_003f"></span><a name="What-is-the-message-size-limit_003f-1"></a>
<h3 class="section">5.3 What is the message size limit?<span class="pull-right"><a class="anchor hidden-xs" href="#What-is-the-message-size-limit_003f-1" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-What-is-the-message-size-limit_003f-1" aria-hidden="true">TOC</a></span></h3>
<p>The message size limit is 1000 kilobytes. Please provide links to larger files
instead of attaching them.
</p>
<a name="Where-can-I-upload-sample-files_003f"></a>
<h3 class="section">5.4 Where can I upload sample files?<span class="pull-right"><a class="anchor hidden-xs" href="#Where-can-I-upload-sample-files_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Where-can-I-upload-sample-files_003f" aria-hidden="true">TOC</a></span></h3>
<p>Anywhere that is not too annoying for us to use.
</p>
<p>Google Drive and Dropbox are acceptable if you need a file host, and
<a href="https://0x0.st/">0x0.st</a> is good for files under 256 MiB.
</p>
<p>Small, short samples are preferred if possible.
</p>
<a name="Will-I-receive-spam-if-I-send-and_002for-subscribe-to-a-mailing-list_003f"></a>
<h3 class="section">5.5 Will I receive spam if I send and/or subscribe to a mailing list?<span class="pull-right"><a class="anchor hidden-xs" href="#Will-I-receive-spam-if-I-send-and_002for-subscribe-to-a-mailing-list_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Will-I-receive-spam-if-I-send-and_002for-subscribe-to-a-mailing-list_003f" aria-hidden="true">TOC</a></span></h3>
<p>Highly unlikely.
</p>
<ul>
<li> The list of subscribed users is not public.
</li><li> Email addresses in the archives are obfuscated.
</li><li> Several unique test email accounts were utilized and none have yet
received any spam.
</li></ul>
<p>However, you may see a spam in the mailing lists on rare occasions:
</p>
<ul>
<li> Spam in the moderation queue may be accidentally approved due to human
error.
</li><li> There have been a few messages from subscribed users who had their own
email addresses hacked and spam messages from (or appearing to be from)
the hacked account were sent to their contacts (a mailing list being a
contact in these cases).
</li><li> If you are subscribed to the bug tracker mailing list (ffmpeg-trac) you
may see the occasional spam as a false bug report, but we take measures
to try to prevent this.
</li></ul>
<a name="How-do-I-filter-mailing-list-messages_003f"></a>
<h3 class="section">5.6 How do I filter mailing list messages?<span class="pull-right"><a class="anchor hidden-xs" href="#How-do-I-filter-mailing-list-messages_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-How-do-I-filter-mailing-list-messages_003f" aria-hidden="true">TOC</a></span></h3>
<p>Use the <em>List-Id</em>. For example, the ffmpeg-user mailing list is
<tt>ffmpeg-user.ffmpeg.org</tt>. You can view the List-Id in the raw message
or headers.
</p>
<p>You can then filter the mailing list messages to their own folder.
</p>
<span id="How-do-I-disable-mail-delivery-without-unsubscribing_003f"></span><a name="How-do-I-disable-mail-delivery-without-unsubscribing_003f-1"></a>
<h3 class="section">5.7 How do I disable mail delivery without unsubscribing?<span class="pull-right"><a class="anchor hidden-xs" href="#How-do-I-disable-mail-delivery-without-unsubscribing_003f-1" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-How-do-I-disable-mail-delivery-without-unsubscribing_003f-1" aria-hidden="true">TOC</a></span></h3>
<p>Sometimes you may want to temporarily stop receiving all mailing list
messages. This &quot;vacation mode&quot; is simple to do:
</p>
<ol>
<li> Go to the <a href="https://lists.ffmpeg.org/mailman/listinfo/ffmpeg-user/">ffmpeg-user mailing list info page</a>
</li><li> Enter your email address in the box at very bottom of the page and click the
<em>Unsubscribe or edit options</em> box.
</li><li> Enter your password and click the <em>Log in</em> button.
</li><li> Look for the <em>Mail delivery</em> option. Here you can disable/enable mail
delivery. If you check <em>Set globally</em> it will apply your choice to all
other FFmpeg mailing lists you are subscribed to.
</li></ol>
<p>Alternatively, from your subscribed address, send a message to <a href="mailto:ffmpeg-user-request@ffmpeg.org">ffmpeg-user-request@ffmpeg.org</a>
with the subject <em>set delivery off</em>. To re-enable mail delivery send a
message to <a href="mailto:ffmpeg-user-request@ffmpeg.org">ffmpeg-user-request@ffmpeg.org</a> with the subject
<em>set delivery on</em>.
</p>
<span id="Why-is-the-mailing-list-munging-my-address_003f"></span><a name="Why-is-the-mailing-list-munging-my-address_003f-1"></a>
<h3 class="section">5.8 Why is the mailing list munging my address?<span class="pull-right"><a class="anchor hidden-xs" href="#Why-is-the-mailing-list-munging-my-address_003f-1" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Why-is-the-mailing-list-munging-my-address_003f-1" aria-hidden="true">TOC</a></span></h3>
<p>This is due to subscribers that use an email service with a DMARC reject policy
which adds difficulties to mailing list operators.
</p>
<p>The mailing list must re-write (munge) the <em>From:</em> header for such users;
otherwise their email service will reject and bounce the message resulting in
automatic unsubscribing from the mailing list.
</p>
<p>When sending a message these users will see <em>via &lt;mailing list name&gt;</em>
added to their name and the <em>From:</em> address munged to the address of
the particular mailing list.
</p>
<p>If you want to avoid this then please use a different email service.
</p>
<p>Note that ffmpeg-devel does not apply any munging as it causes issues with
patch authorship. As a result users with an email service with a DMARC reject
policy may be automatically unsubscribed due to rejected and bounced messages.
</p>
<a name="Rules-and-Etiquette"></a>
<h2 class="chapter">6 Rules and Etiquette<span class="pull-right"><a class="anchor hidden-xs" href="#Rules-and-Etiquette" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Rules-and-Etiquette" aria-hidden="true">TOC</a></span></h2>
<a name="What-are-the-rules-and-the-proper-etiquette_003f"></a>
<h3 class="section">6.1 What are the rules and the proper etiquette?<span class="pull-right"><a class="anchor hidden-xs" href="#What-are-the-rules-and-the-proper-etiquette_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-What-are-the-rules-and-the-proper-etiquette_003f" aria-hidden="true">TOC</a></span></h3>
<p>There may seem to be many things to remember, but we want to help and
following these guidelines will allow you to get answers more quickly
and help avoid getting ignored.
</p>
<ul>
<li> Always show your actual, unscripted <code>ffmpeg</code> command and the
complete, uncut console output from your command.
</li><li> Use the most simple and minimal command that still shows the issue you
are encountering.
</li><li> Provide all necessary information so others can attempt to duplicate
your issue. This includes the actual command, complete uncut console
output, and any inputs that are required to duplicate the issue.
</li><li> Use the latest <code>ffmpeg</code> build you can get. See the <a href="https://ffmpeg.org/download.html">FFmpeg Download</a>
page for links to recent builds for Linux, macOS, and Windows. Or
compile from the current git master branch.
</li><li> Avoid <a href="https://en.wikipedia.org/wiki/Posting_style#Top-posting">top-posting</a>.
Also see <a href="#What-is-top_002dposting_003f">What is top-posting?</a>
</li><li> Avoid hijacking threads. Thread hijacking is replying to a message and
changing the subject line to something unrelated to the original thread.
Most email clients will still show the renamed message under the
original thread. This can be confusing and these types of messages are
often ignored.
</li><li> Do not send screenshots. Copy and paste console text instead of making
screenshots of the text.
</li><li> Avoid sending email disclaimers and legalese if possible as this is a
public list.
</li><li> Avoid using the <code>-loglevel debug</code>, <code>-loglevel quiet</code>, and
<code>-hide_banner</code> options unless requested to do so.
</li><li> If you attach files avoid compressing small files. Uncompressed is
preferred.
</li><li> Please do not send HTML-only messages. The mailing list will ignore the
HTML component of your message. Most mail clients will automatically
include a text component: this is what the mailing list will use.
</li><li> Configuring your mail client to break lines after 70 or so characters is
recommended.
</li><li> Avoid sending the same message to multiple mailing lists.
</li><li> Please follow our <a href="https://ffmpeg.org/developer.html#Code-of-conduct">Code of Conduct</a>.
</li></ul>
<a name="Help"></a>
<h2 class="chapter">7 Help<span class="pull-right"><a class="anchor hidden-xs" href="#Help" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Help" aria-hidden="true">TOC</a></span></h2>
<a name="Why-am-I-not-receiving-any-messages_003f"></a>
<h3 class="section">7.1 Why am I not receiving any messages?<span class="pull-right"><a class="anchor hidden-xs" href="#Why-am-I-not-receiving-any-messages_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Why-am-I-not-receiving-any-messages_003f" aria-hidden="true">TOC</a></span></h3>
<p>Some email providers have blacklists or spam filters that block or mark
the mailing list messages as false positives. Unfortunately, the user is
often not aware of this and is often out of their control.
</p>
<p>When possible we attempt to notify the provider to be removed from the
blacklists or filters.
</p>
<a name="Why-are-my-sent-messages-not-showing-up_003f"></a>
<h3 class="section">7.2 Why are my sent messages not showing up?<span class="pull-right"><a class="anchor hidden-xs" href="#Why-are-my-sent-messages-not-showing-up_003f" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Why-are-my-sent-messages-not-showing-up_003f" aria-hidden="true">TOC</a></span></h3>
<p>Excluding <a href="#Why-is-my-message-awaiting-moderator-approval_003f">messages that are held in the moderation queue</a>
there are a few other reasons why your messages may fail to appear:
</p>
<ul>
<li> HTML-only messages are ignored by the mailing lists. Most mail clients
automatically include a text component alongside HTML email: this is what
the mailing list will use. If it does not then consider your client to be
broken, because sending a text component along with the HTML component to
form a multi-part message is recommended by email standards.
</li><li> Check your spam folder.
</li></ul>
<span id="Why-do-I-keep-getting-unsubscribed-from-ffmpeg_002ddevel_003f"></span><a name="Why-do-I-keep-getting-unsubscribed-from-ffmpeg_002ddevel_003f-1"></a>
<h3 class="section">7.3 Why do I keep getting unsubscribed from ffmpeg-devel?<span class="pull-right"><a class="anchor hidden-xs" href="#Why-do-I-keep-getting-unsubscribed-from-ffmpeg_002ddevel_003f-1" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Why-do-I-keep-getting-unsubscribed-from-ffmpeg_002ddevel_003f-1" aria-hidden="true">TOC</a></span></h3>
<p>Users with an email service that has a DMARC reject or quarantine policy may be
automatically unsubscribed from the ffmpeg-devel mailing list due to the mailing
list messages being continuously rejected and bounced back.
</p>
<p>Consider using a different email service.
</p>
<span id="Who-do-I-contact-if-I-have-a-problem-with-the-mailing-list_003f"></span><a name="Who-do-I-contact-if-I-have-a-problem-with-the-mailing-list_003f-1"></a>
<h3 class="section">7.4 Who do I contact if I have a problem with the mailing list?<span class="pull-right"><a class="anchor hidden-xs" href="#Who-do-I-contact-if-I-have-a-problem-with-the-mailing-list_003f-1" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Who-do-I-contact-if-I-have-a-problem-with-the-mailing-list_003f-1" aria-hidden="true">TOC</a></span></h3>
<p>Send a message to <a href="mailto:ffmpeg-user-owner@ffmpeg.org">ffmpeg-user-owner@ffmpeg.org</a>.
</p>
<p style="font-size: small;">
This document was generated using <a href="https://www.gnu.org/software/texinfo/"><em>makeinfo</em></a>.
</p>
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<head>
<meta charset="utf-8">
<title>
NUT
</title>
<meta name="viewport" content="width=device-width,initial-scale=1.0">
<link rel="stylesheet" type="text/css" href="bootstrap.min.css">
<link rel="stylesheet" type="text/css" href="style.min.css">
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<body>
<div class="container">
<h1>
NUT
</h1>
<div align="center">
</div>
<a name="SEC_Top"></a>
<div class="Contents_element" id="SEC_Contents">
<h2 class="contents-heading">Table of Contents</h2>
<div class="contents">
<ul class="no-bullet">
<li><a id="toc-Description" href="#Description">1 Description</a></li>
<li><a id="toc-Modes" href="#Modes">2 Modes</a>
<ul class="no-bullet">
<li><a id="toc-BROADCAST" href="#BROADCAST">2.1 BROADCAST</a></li>
<li><a id="toc-PIPE" href="#PIPE">2.2 PIPE</a></li>
</ul></li>
<li><a id="toc-Container_002dspecific-codec-tags" href="#Container_002dspecific-codec-tags">3 Container-specific codec tags</a>
<ul class="no-bullet">
<li><a id="toc-Generic-raw-YUVA-formats" href="#Generic-raw-YUVA-formats">3.1 Generic raw YUVA formats</a></li>
<li><a id="toc-Raw-Audio" href="#Raw-Audio">3.2 Raw Audio</a></li>
<li><a id="toc-Subtitles" href="#Subtitles">3.3 Subtitles</a></li>
<li><a id="toc-Raw-Data" href="#Raw-Data">3.4 Raw Data</a></li>
<li><a id="toc-Codecs" href="#Codecs">3.5 Codecs</a></li>
</ul></li>
</ul>
</div>
</div>
<a name="Description"></a>
<h2 class="chapter">1 Description<span class="pull-right"><a class="anchor hidden-xs" href="#Description" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Description" aria-hidden="true">TOC</a></span></h2>
<p>NUT is a low overhead generic container format. It stores audio, video,
subtitle and user-defined streams in a simple, yet efficient, way.
</p>
<p>It was created by a group of FFmpeg and MPlayer developers in 2003
and was finalized in 2008.
</p>
<p>The official nut specification is at svn://svn.mplayerhq.hu/nut
In case of any differences between this text and the official specification,
the official specification shall prevail.
</p>
<a name="Modes"></a>
<h2 class="chapter">2 Modes<span class="pull-right"><a class="anchor hidden-xs" href="#Modes" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Modes" aria-hidden="true">TOC</a></span></h2>
<p>NUT has some variants signaled by using the flags field in its main header.
</p>
<table>
<tr><td width="40%">BROADCAST</td><td width="40%">Extend the syncpoint to report the sender wallclock</td></tr>
<tr><td width="40%">PIPE</td><td width="40%">Omit completely the syncpoint</td></tr>
</table>
<a name="BROADCAST"></a>
<h3 class="section">2.1 BROADCAST<span class="pull-right"><a class="anchor hidden-xs" href="#BROADCAST" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-BROADCAST" aria-hidden="true">TOC</a></span></h3>
<p>The BROADCAST variant provides a secondary time reference to facilitate
detecting endpoint latency and network delays.
It assumes all the endpoint clocks are synchronized.
To be used in real-time scenarios.
</p>
<a name="PIPE"></a>
<h3 class="section">2.2 PIPE<span class="pull-right"><a class="anchor hidden-xs" href="#PIPE" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-PIPE" aria-hidden="true">TOC</a></span></h3>
<p>The PIPE variant assumes NUT is used as non-seekable intermediate container,
by not using syncpoint removes unneeded overhead and reduces the overall
memory usage.
</p>
<a name="Container_002dspecific-codec-tags"></a>
<h2 class="chapter">3 Container-specific codec tags<span class="pull-right"><a class="anchor hidden-xs" href="#Container_002dspecific-codec-tags" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Container_002dspecific-codec-tags" aria-hidden="true">TOC</a></span></h2>
<a name="Generic-raw-YUVA-formats"></a>
<h3 class="section">3.1 Generic raw YUVA formats<span class="pull-right"><a class="anchor hidden-xs" href="#Generic-raw-YUVA-formats" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Generic-raw-YUVA-formats" aria-hidden="true">TOC</a></span></h3>
<p>Since many exotic planar YUVA pixel formats are not considered by
the AVI/QuickTime FourCC lists, the following scheme is adopted for
representing them.
</p>
<p>The first two bytes can contain the values:
Y1 = only Y
Y2 = Y+A
Y3 = YUV
Y4 = YUVA
</p>
<p>The third byte represents the width and height chroma subsampling
values for the UV planes, that is the amount to shift the luma
width/height right to find the chroma width/height.
</p>
<p>The fourth byte is the number of bits used (8, 16, ...).
</p>
<p>If the order of bytes is inverted, that means that each component has
to be read big-endian.
</p>
<a name="Raw-Audio"></a>
<h3 class="section">3.2 Raw Audio<span class="pull-right"><a class="anchor hidden-xs" href="#Raw-Audio" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Raw-Audio" aria-hidden="true">TOC</a></span></h3>
<table>
<tr><td width="40%">ALAW</td><td width="40%">A-LAW</td></tr>
<tr><td width="40%">ULAW</td><td width="40%">MU-LAW</td></tr>
<tr><td width="40%">P&lt;type&gt;&lt;interleaving&gt;&lt;bits&gt;</td><td width="40%">little-endian PCM</td></tr>
<tr><td width="40%">&lt;bits&gt;&lt;interleaving&gt;&lt;type&gt;P</td><td width="40%">big-endian PCM</td></tr>
</table>
<p>&lt;type&gt; is S for signed integer, U for unsigned integer, F for IEEE float
&lt;interleaving&gt; is D for default, P is for planar.
&lt;bits&gt; is 8/16/24/32
</p>
<div class="example">
<pre class="example">PFD[32] would for example be signed 32 bit little-endian IEEE float
</pre></div>
<a name="Subtitles"></a>
<h3 class="section">3.3 Subtitles<span class="pull-right"><a class="anchor hidden-xs" href="#Subtitles" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Subtitles" aria-hidden="true">TOC</a></span></h3>
<table>
<tr><td width="40%">UTF8</td><td width="40%">Raw UTF-8</td></tr>
<tr><td width="40%">SSA[0]</td><td width="40%">SubStation Alpha</td></tr>
<tr><td width="40%">DVDS</td><td width="40%">DVD subtitles</td></tr>
<tr><td width="40%">DVBS</td><td width="40%">DVB subtitles</td></tr>
</table>
<a name="Raw-Data"></a>
<h3 class="section">3.4 Raw Data<span class="pull-right"><a class="anchor hidden-xs" href="#Raw-Data" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Raw-Data" aria-hidden="true">TOC</a></span></h3>
<table>
<tr><td width="40%">UTF8</td><td width="40%">Raw UTF-8</td></tr>
</table>
<a name="Codecs"></a>
<h3 class="section">3.5 Codecs<span class="pull-right"><a class="anchor hidden-xs" href="#Codecs" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Codecs" aria-hidden="true">TOC</a></span></h3>
<table>
<tr><td width="40%">3IV1</td><td width="40%">non-compliant MPEG-4 generated by old 3ivx</td></tr>
<tr><td width="40%">ASV1</td><td width="40%">Asus Video</td></tr>
<tr><td width="40%">ASV2</td><td width="40%">Asus Video 2</td></tr>
<tr><td width="40%">CVID</td><td width="40%">Cinepak</td></tr>
<tr><td width="40%">CYUV</td><td width="40%">Creative YUV</td></tr>
<tr><td width="40%">DIVX</td><td width="40%">non-compliant MPEG-4 generated by old DivX</td></tr>
<tr><td width="40%">DUCK</td><td width="40%">Truemotion 1</td></tr>
<tr><td width="40%">FFV1</td><td width="40%">FFmpeg video 1</td></tr>
<tr><td width="40%">FFVH</td><td width="40%">FFmpeg Huffyuv</td></tr>
<tr><td width="40%">H261</td><td width="40%">ITU H.261</td></tr>
<tr><td width="40%">H262</td><td width="40%">ITU H.262</td></tr>
<tr><td width="40%">H263</td><td width="40%">ITU H.263</td></tr>
<tr><td width="40%">H264</td><td width="40%">ITU H.264</td></tr>
<tr><td width="40%">HFYU</td><td width="40%">Huffyuv</td></tr>
<tr><td width="40%">I263</td><td width="40%">Intel H.263</td></tr>
<tr><td width="40%">IV31</td><td width="40%">Indeo 3.1</td></tr>
<tr><td width="40%">IV32</td><td width="40%">Indeo 3.2</td></tr>
<tr><td width="40%">IV50</td><td width="40%">Indeo 5.0</td></tr>
<tr><td width="40%">LJPG</td><td width="40%">ITU JPEG (lossless)</td></tr>
<tr><td width="40%">MJLS</td><td width="40%">ITU JPEG-LS</td></tr>
<tr><td width="40%">MJPG</td><td width="40%">ITU JPEG</td></tr>
<tr><td width="40%">MPG4</td><td width="40%">MS MPEG-4v1 (not ISO MPEG-4)</td></tr>
<tr><td width="40%">MP42</td><td width="40%">MS MPEG-4v2</td></tr>
<tr><td width="40%">MP43</td><td width="40%">MS MPEG-4v3</td></tr>
<tr><td width="40%">MP4V</td><td width="40%">ISO MPEG-4 Part 2 Video (from old encoders)</td></tr>
<tr><td width="40%">mpg1</td><td width="40%">ISO MPEG-1 Video</td></tr>
<tr><td width="40%">mpg2</td><td width="40%">ISO MPEG-2 Video</td></tr>
<tr><td width="40%">MRLE</td><td width="40%">MS RLE</td></tr>
<tr><td width="40%">MSVC</td><td width="40%">MS Video 1</td></tr>
<tr><td width="40%">RT21</td><td width="40%">Indeo 2.1</td></tr>
<tr><td width="40%">RV10</td><td width="40%">RealVideo 1.0</td></tr>
<tr><td width="40%">RV20</td><td width="40%">RealVideo 2.0</td></tr>
<tr><td width="40%">RV30</td><td width="40%">RealVideo 3.0</td></tr>
<tr><td width="40%">RV40</td><td width="40%">RealVideo 4.0</td></tr>
<tr><td width="40%">SNOW</td><td width="40%">FFmpeg Snow</td></tr>
<tr><td width="40%">SVQ1</td><td width="40%">Sorenson Video 1</td></tr>
<tr><td width="40%">SVQ3</td><td width="40%">Sorenson Video 3</td></tr>
<tr><td width="40%">theo</td><td width="40%">Xiph Theora</td></tr>
<tr><td width="40%">TM20</td><td width="40%">Truemotion 2.0</td></tr>
<tr><td width="40%">UMP4</td><td width="40%">non-compliant MPEG-4 generated by UB Video MPEG-4</td></tr>
<tr><td width="40%">VCR1</td><td width="40%">ATI VCR1</td></tr>
<tr><td width="40%">VP30</td><td width="40%">VP 3.0</td></tr>
<tr><td width="40%">VP31</td><td width="40%">VP 3.1</td></tr>
<tr><td width="40%">VP50</td><td width="40%">VP 5.0</td></tr>
<tr><td width="40%">VP60</td><td width="40%">VP 6.0</td></tr>
<tr><td width="40%">VP61</td><td width="40%">VP 6.1</td></tr>
<tr><td width="40%">VP62</td><td width="40%">VP 6.2</td></tr>
<tr><td width="40%">VP70</td><td width="40%">VP 7.0</td></tr>
<tr><td width="40%">WMV1</td><td width="40%">MS WMV7</td></tr>
<tr><td width="40%">WMV2</td><td width="40%">MS WMV8</td></tr>
<tr><td width="40%">WMV3</td><td width="40%">MS WMV9</td></tr>
<tr><td width="40%">WV1F</td><td width="40%">non-compliant MPEG-4 generated by ?</td></tr>
<tr><td width="40%">WVC1</td><td width="40%">VC-1</td></tr>
<tr><td width="40%">XVID</td><td width="40%">non-compliant MPEG-4 generated by old Xvid</td></tr>
<tr><td width="40%">XVIX</td><td width="40%">non-compliant MPEG-4 generated by old Xvid with interlacing bug</td></tr>
</table>
<p style="font-size: small;">
This document was generated using <a href="https://www.gnu.org/software/texinfo/"><em>makeinfo</em></a>.
</p>
</div>
</body>
</html>

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<title>
Platform Specific Information
</title>
<meta name="viewport" content="width=device-width,initial-scale=1.0">
<link rel="stylesheet" type="text/css" href="bootstrap.min.css">
<link rel="stylesheet" type="text/css" href="style.min.css">
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Platform Specific Information
</h1>
<div align="center">
</div>
<a name="SEC_Top"></a>
<div class="Contents_element" id="SEC_Contents">
<h2 class="contents-heading">Table of Contents</h2>
<div class="contents">
<ul class="no-bullet">
<li><a id="toc-Unix_002dlike" href="#Unix_002dlike">1 Unix-like</a>
<ul class="no-bullet">
<li><a id="toc-Advanced-linking-configuration" href="#Advanced-linking-configuration">1.1 Advanced linking configuration</a></li>
<li><a id="toc-BSD" href="#BSD">1.2 BSD</a></li>
<li><a id="toc-_0028Open_0029Solaris" href="#g_t_0028Open_0029Solaris">1.3 (Open)Solaris</a></li>
<li><a id="toc-Darwin-_0028Mac-OS-X_002c-iPhone_0029" href="#Darwin-_0028Mac-OS-X_002c-iPhone_0029">1.4 Darwin (Mac OS X, iPhone)</a></li>
</ul></li>
<li><a id="toc-DOS" href="#DOS">2 DOS</a></li>
<li><a id="toc-OS_002f2" href="#OS_002f2">3 OS/2</a></li>
<li><a id="toc-Windows" href="#Windows">4 Windows</a>
<ul class="no-bullet">
<li><a id="toc-Native-Windows-compilation-using-MinGW-or-MinGW_002dw64" href="#Native-Windows-compilation-using-MinGW-or-MinGW_002dw64">4.1 Native Windows compilation using MinGW or MinGW-w64</a>
<ul class="no-bullet">
<li><a id="toc-Native-Windows-compilation-using-MSYS2" href="#Native-Windows-compilation-using-MSYS2">4.1.1 Native Windows compilation using MSYS2</a></li>
</ul></li>
<li><a id="toc-Microsoft-Visual-C_002b_002b-or-Intel-C_002b_002b-Compiler-for-Windows" href="#Microsoft-Visual-C_002b_002b-or-Intel-C_002b_002b-Compiler-for-Windows">4.2 Microsoft Visual C++ or Intel C++ Compiler for Windows</a>
<ul class="no-bullet">
<li><a id="toc-Linking-to-FFmpeg-with-Microsoft-Visual-C_002b_002b" href="#Linking-to-FFmpeg-with-Microsoft-Visual-C_002b_002b">4.2.1 Linking to FFmpeg with Microsoft Visual C++</a></li>
</ul></li>
<li><a id="toc-Cross-compilation-for-Windows-with-Linux-1" href="#Cross-compilation-for-Windows-with-Linux-1">4.3 Cross compilation for Windows with Linux</a></li>
<li><a id="toc-Compilation-under-Cygwin" href="#Compilation-under-Cygwin">4.4 Compilation under Cygwin</a></li>
<li><a id="toc-Crosscompilation-for-Windows-under-Cygwin" href="#Crosscompilation-for-Windows-under-Cygwin">4.5 Crosscompilation for Windows under Cygwin</a></li>
</ul></li>
</ul>
</div>
</div>
<a name="Unix_002dlike"></a>
<h2 class="chapter">1 Unix-like<span class="pull-right"><a class="anchor hidden-xs" href="#Unix_002dlike" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Unix_002dlike" aria-hidden="true">TOC</a></span></h2>
<p>Some parts of FFmpeg cannot be built with version 2.15 of the GNU
assembler which is still provided by a few AMD64 distributions. To
make sure your compiler really uses the required version of gas
after a binutils upgrade, run:
</p>
<div class="example">
<pre class="example">$(gcc -print-prog-name=as) --version
</pre></div>
<p>If not, then you should install a different compiler that has no
hard-coded path to gas. In the worst case pass <code>--disable-asm</code>
to configure.
</p>
<a name="Advanced-linking-configuration"></a>
<h3 class="section">1.1 Advanced linking configuration<span class="pull-right"><a class="anchor hidden-xs" href="#Advanced-linking-configuration" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Advanced-linking-configuration" aria-hidden="true">TOC</a></span></h3>
<p>If you compiled FFmpeg libraries statically and you want to use them to
build your own shared library, you may need to force PIC support (with
<code>--enable-pic</code> during FFmpeg configure) and add the following option
to your project LDFLAGS:
</p>
<div class="example">
<pre class="example">-Wl,-Bsymbolic
</pre></div>
<p>If your target platform requires position independent binaries, you should
pass the correct linking flag (e.g. <code>-pie</code>) to <code>--extra-ldexeflags</code>.
</p>
<a name="BSD"></a>
<h3 class="section">1.2 BSD<span class="pull-right"><a class="anchor hidden-xs" href="#BSD" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-BSD" aria-hidden="true">TOC</a></span></h3>
<p>BSD make will not build FFmpeg, you need to install and use GNU Make
(<code>gmake</code>).
</p>
<a name="g_t_0028Open_0029Solaris"></a>
<h3 class="section">1.3 (Open)Solaris<span class="pull-right"><a class="anchor hidden-xs" href="#_0028Open_0029Solaris" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-_0028Open_0029Solaris" aria-hidden="true">TOC</a></span></h3>
<p>GNU Make is required to build FFmpeg, so you have to invoke (<code>gmake</code>),
standard Solaris Make will not work. When building with a non-c99 front-end
(gcc, generic suncc) add either <code>--extra-libs=/usr/lib/values-xpg6.o</code>
or <code>--extra-libs=/usr/lib/64/values-xpg6.o</code> to the configure options
since the libc is not c99-compliant by default. The probes performed by
configure may raise an exception leading to the death of configure itself
due to a bug in the system shell. Simply invoke a different shell such as
bash directly to work around this:
</p>
<div class="example">
<pre class="example">bash ./configure
</pre></div>
<span id="Darwin"></span><a name="Darwin-_0028Mac-OS-X_002c-iPhone_0029"></a>
<h3 class="section">1.4 Darwin (Mac OS X, iPhone)<span class="pull-right"><a class="anchor hidden-xs" href="#Darwin-_0028Mac-OS-X_002c-iPhone_0029" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Darwin-_0028Mac-OS-X_002c-iPhone_0029" aria-hidden="true">TOC</a></span></h3>
<p>The toolchain provided with Xcode is sufficient to build the basic
unaccelerated code.
</p>
<p>Mac OS X on PowerPC or ARM (iPhone) requires a preprocessor from
<a href="https://github.com/FFmpeg/gas-preprocessor">https://github.com/FFmpeg/gas-preprocessor</a> or
<a href="https://github.com/yuvi/gas-preprocessor">https://github.com/yuvi/gas-preprocessor</a>(currently outdated) to build the optimized
assembly functions. Put the Perl script somewhere
in your PATH, FFmpeg&rsquo;s configure will pick it up automatically.
</p>
<p>Mac OS X on amd64 and x86 requires <code>nasm</code> to build most of the
optimized assembly functions. <a href="http://www.finkproject.org/">Fink</a>,
<a href="https://wiki.gentoo.org/wiki/Project:Prefix">Gentoo Prefix</a>,
<a href="https://mxcl.github.com/homebrew/">Homebrew</a>
or <a href="http://www.macports.org">MacPorts</a> can easily provide it.
</p>
<a name="DOS"></a>
<h2 class="chapter">2 DOS<span class="pull-right"><a class="anchor hidden-xs" href="#DOS" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-DOS" aria-hidden="true">TOC</a></span></h2>
<p>Using a cross-compiler is preferred for various reasons.
<a href="http://www.delorie.com/howto/djgpp/linux-x-djgpp.html">http://www.delorie.com/howto/djgpp/linux-x-djgpp.html</a>
</p>
<a name="OS_002f2"></a>
<h2 class="chapter">3 OS/2<span class="pull-right"><a class="anchor hidden-xs" href="#OS_002f2" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-OS_002f2" aria-hidden="true">TOC</a></span></h2>
<p>For information about compiling FFmpeg on OS/2 see
<a href="http://www.edm2.com/index.php/FFmpeg">http://www.edm2.com/index.php/FFmpeg</a>.
</p>
<a name="Windows"></a>
<h2 class="chapter">4 Windows<span class="pull-right"><a class="anchor hidden-xs" href="#Windows" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Windows" aria-hidden="true">TOC</a></span></h2>
<p>To get help and instructions for building FFmpeg under Windows, check out
the FFmpeg Windows Help Forum at <a href="http://ffmpeg.zeranoe.com/forum/">http://ffmpeg.zeranoe.com/forum/</a>.
</p>
<a name="Native-Windows-compilation-using-MinGW-or-MinGW_002dw64"></a>
<h3 class="section">4.1 Native Windows compilation using MinGW or MinGW-w64<span class="pull-right"><a class="anchor hidden-xs" href="#Native-Windows-compilation-using-MinGW-or-MinGW_002dw64" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Native-Windows-compilation-using-MinGW-or-MinGW_002dw64" aria-hidden="true">TOC</a></span></h3>
<p>FFmpeg can be built to run natively on Windows using the MinGW-w64
toolchain. Install the latest versions of MSYS2 and MinGW-w64 from
<a href="http://msys2.github.io/">http://msys2.github.io/</a> and/or <a href="http://mingw-w64.sourceforge.net/">http://mingw-w64.sourceforge.net/</a>.
You can find detailed installation instructions in the download section and
the FAQ.
</p>
<p>Notes:
</p>
<ul>
<li> Building for the MSYS environment is discouraged, MSYS2 provides a full
MinGW-w64 environment through <samp>mingw64_shell.bat</samp> or
<samp>mingw32_shell.bat</samp> that should be used instead of the environment
provided by <samp>msys2_shell.bat</samp>.
</li><li> Building using MSYS2 can be sped up by disabling implicit rules in the
Makefile by calling <code>make -r</code> instead of plain <code>make</code>. This
speed up is close to non-existent for normal one-off builds and is only
noticeable when running make for a second time (for example during
<code>make install</code>).
</li><li> In order to compile FFplay, you must have the MinGW development library
of <a href="http://www.libsdl.org/">SDL</a> and <code>pkg-config</code> installed.
</li><li> By using <code>./configure --enable-shared</code> when configuring FFmpeg,
you can build the FFmpeg libraries (e.g. libavutil, libavcodec,
libavformat) as DLLs.
</li></ul>
<a name="Native-Windows-compilation-using-MSYS2"></a>
<h4 class="subsection">4.1.1 Native Windows compilation using MSYS2<span class="pull-right"><a class="anchor hidden-xs" href="#Native-Windows-compilation-using-MSYS2" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Native-Windows-compilation-using-MSYS2" aria-hidden="true">TOC</a></span></h4>
<p>The MSYS2 MinGW-w64 environment provides ready to use toolchains and dependencies
through <code>pacman</code>.
</p>
<p>Make sure to use <samp>mingw64_shell.bat</samp> or <samp>mingw32_shell.bat</samp> to have
the correct MinGW-w64 environment. The default install provides shortcuts to
them under <code>MinGW-w64 Win64 Shell</code> and <code>MinGW-w64 Win32 Shell</code>.
</p>
<div class="example">
<pre class="example"># normal msys2 packages
pacman -S make pkgconf diffutils
# mingw-w64 packages and toolchains
pacman -S mingw-w64-x86_64-nasm mingw-w64-x86_64-gcc mingw-w64-x86_64-SDL2
</pre></div>
<p>To target 32 bits replace <code>x86_64</code> with <code>i686</code> in the command above.
</p>
<a name="Microsoft-Visual-C_002b_002b-or-Intel-C_002b_002b-Compiler-for-Windows"></a>
<h3 class="section">4.2 Microsoft Visual C++ or Intel C++ Compiler for Windows<span class="pull-right"><a class="anchor hidden-xs" href="#Microsoft-Visual-C_002b_002b-or-Intel-C_002b_002b-Compiler-for-Windows" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Microsoft-Visual-C_002b_002b-or-Intel-C_002b_002b-Compiler-for-Windows" aria-hidden="true">TOC</a></span></h3>
<p>FFmpeg can be built with MSVC 2013 or later.
</p>
<p>You will need the following prerequisites:
</p>
<ul>
<li> <a href="http://msys2.github.io/">MSYS2</a>
</li><li> <a href="http://www.nasm.us/">NASM</a>
(Also available via MSYS2&rsquo;s package manager.)
</li></ul>
<p>To set up a proper environment in MSYS2, you need to run <code>msys_shell.bat</code> from
the Visual Studio or Intel Compiler command prompt.
</p>
<p>Place <code>yasm.exe</code> somewhere in your <code>PATH</code>.
</p>
<p>Next, make sure any other headers and libs you want to use, such as zlib, are
located in a spot that the compiler can see. Do so by modifying the <code>LIB</code>
and <code>INCLUDE</code> environment variables to include the <strong>Windows-style</strong>
paths to these directories. Alternatively, you can try to use the
<code>--extra-cflags</code>/<code>--extra-ldflags</code> configure options.
</p>
<p>Finally, run:
</p>
<div class="example">
<pre class="example">For MSVC:
./configure --toolchain=msvc
For ICL:
./configure --toolchain=icl
make
make install
</pre></div>
<p>If you wish to compile shared libraries, add <code>--enable-shared</code> to your
configure options. Note that due to the way MSVC and ICL handle DLL imports and
exports, you cannot compile static and shared libraries at the same time, and
enabling shared libraries will automatically disable the static ones.
</p>
<p>Notes:
</p>
<ul>
<li> If you wish to build with zlib support, you will have to grab a compatible
zlib binary from somewhere, with an MSVC import lib, or if you wish to link
statically, you can follow the instructions below to build a compatible
<code>zlib.lib</code> with MSVC. Regardless of which method you use, you must still
follow step 3, or compilation will fail.
<ol>
<li> Grab the <a href="http://zlib.net/">zlib sources</a>.
</li><li> Edit <code>win32/Makefile.msc</code> so that it uses -MT instead of -MD, since
this is how FFmpeg is built as well.
</li><li> Edit <code>zconf.h</code> and remove its inclusion of <code>unistd.h</code>. This gets
erroneously included when building FFmpeg.
</li><li> Run <code>nmake -f win32/Makefile.msc</code>.
</li><li> Move <code>zlib.lib</code>, <code>zconf.h</code>, and <code>zlib.h</code> to somewhere MSVC
can see.
</li></ol>
</li><li> FFmpeg has been tested with the following on i686 and x86_64:
<ul>
<li> Visual Studio 2013 Pro and Express
</li><li> Intel Composer XE 2013
</li><li> Intel Composer XE 2013 SP1
</li></ul>
<p>Anything else is not officially supported.
</p>
</li></ul>
<a name="Linking-to-FFmpeg-with-Microsoft-Visual-C_002b_002b"></a>
<h4 class="subsection">4.2.1 Linking to FFmpeg with Microsoft Visual C++<span class="pull-right"><a class="anchor hidden-xs" href="#Linking-to-FFmpeg-with-Microsoft-Visual-C_002b_002b" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Linking-to-FFmpeg-with-Microsoft-Visual-C_002b_002b" aria-hidden="true">TOC</a></span></h4>
<p>If you plan to link with MSVC-built static libraries, you will need
to make sure you have <code>Runtime Library</code> set to
<code>Multi-threaded (/MT)</code> in your project&rsquo;s settings.
</p>
<p>You will need to define <code>inline</code> to something MSVC understands:
</p><div class="example">
<pre class="example">#define inline __inline
</pre></div>
<p>Also note, that as stated in <strong>Microsoft Visual C++</strong>, you will need
an MSVC-compatible <a href="http://code.google.com/p/msinttypes/">inttypes.h</a>.
</p>
<p>If you plan on using import libraries created by dlltool, you must
set <code>References</code> to <code>No (/OPT:NOREF)</code> under the linker optimization
settings, otherwise the resulting binaries will fail during runtime.
This is not required when using import libraries generated by <code>lib.exe</code>.
This issue is reported upstream at
<a href="http://sourceware.org/bugzilla/show_bug.cgi?id=12633">http://sourceware.org/bugzilla/show_bug.cgi?id=12633</a>.
</p>
<p>To create import libraries that work with the <code>/OPT:REF</code> option
(which is enabled by default in Release mode), follow these steps:
</p>
<ol>
<li> Open the <em>Visual Studio Command Prompt</em>.
<p>Alternatively, in a normal command line prompt, call <samp>vcvars32.bat</samp>
which sets up the environment variables for the Visual C++ tools
(the standard location for this file is something like
<samp>C:\Program Files (x86_\Microsoft Visual Studio 10.0\VC\bin\vcvars32.bat</samp>).
</p>
</li><li> Enter the <samp>bin</samp> directory where the created LIB and DLL files
are stored.
</li><li> Generate new import libraries with <code>lib.exe</code>:
<div class="example">
<pre class="example">lib /machine:i386 /def:..\lib\foo-version.def /out:foo.lib
</pre></div>
<p>Replace <code>foo-version</code> and <code>foo</code> with the respective library names.
</p>
</li></ol>
<span id="Cross-compilation-for-Windows-with-Linux"></span><a name="Cross-compilation-for-Windows-with-Linux-1"></a>
<h3 class="section">4.3 Cross compilation for Windows with Linux<span class="pull-right"><a class="anchor hidden-xs" href="#Cross-compilation-for-Windows-with-Linux-1" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Cross-compilation-for-Windows-with-Linux-1" aria-hidden="true">TOC</a></span></h3>
<p>You must use the MinGW cross compilation tools available at
<a href="http://www.mingw.org/">http://www.mingw.org/</a>.
</p>
<p>Then configure FFmpeg with the following options:
</p><div class="example">
<pre class="example">./configure --target-os=mingw32 --cross-prefix=i386-mingw32msvc-
</pre></div>
<p>(you can change the cross-prefix according to the prefix chosen for the
MinGW tools).
</p>
<p>Then you can easily test FFmpeg with <a href="http://www.winehq.com/">Wine</a>.
</p>
<a name="Compilation-under-Cygwin"></a>
<h3 class="section">4.4 Compilation under Cygwin<span class="pull-right"><a class="anchor hidden-xs" href="#Compilation-under-Cygwin" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Compilation-under-Cygwin" aria-hidden="true">TOC</a></span></h3>
<p>Please use Cygwin 1.7.x as the obsolete 1.5.x Cygwin versions lack
llrint() in its C library.
</p>
<p>Install your Cygwin with all the &quot;Base&quot; packages, plus the
following &quot;Devel&quot; ones:
</p><div class="example">
<pre class="example">binutils, gcc4-core, make, git, mingw-runtime, texinfo
</pre></div>
<p>In order to run FATE you will also need the following &quot;Utils&quot; packages:
</p><div class="example">
<pre class="example">diffutils
</pre></div>
<p>If you want to build FFmpeg with additional libraries, download Cygwin
&quot;Devel&quot; packages for Ogg and Vorbis from any Cygwin packages repository:
</p><div class="example">
<pre class="example">libogg-devel, libvorbis-devel
</pre></div>
<p>These library packages are only available from
<a href="http://sourceware.org/cygwinports/">Cygwin Ports</a>:
</p>
<div class="example">
<pre class="example">yasm, libSDL-devel, libgsm-devel, libmp3lame-devel,
speex-devel, libtheora-devel, libxvidcore-devel
</pre></div>
<p>The recommendation for x264 is to build it from source, as it evolves too
quickly for Cygwin Ports to be up to date.
</p>
<a name="Crosscompilation-for-Windows-under-Cygwin"></a>
<h3 class="section">4.5 Crosscompilation for Windows under Cygwin<span class="pull-right"><a class="anchor hidden-xs" href="#Crosscompilation-for-Windows-under-Cygwin" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Crosscompilation-for-Windows-under-Cygwin" aria-hidden="true">TOC</a></span></h3>
<p>With Cygwin you can create Windows binaries that do not need the cygwin1.dll.
</p>
<p>Just install your Cygwin as explained before, plus these additional
&quot;Devel&quot; packages:
</p><div class="example">
<pre class="example">gcc-mingw-core, mingw-runtime, mingw-zlib
</pre></div>
<p>and add some special flags to your configure invocation.
</p>
<p>For a static build run
</p><div class="example">
<pre class="example">./configure --target-os=mingw32 --extra-cflags=-mno-cygwin --extra-libs=-mno-cygwin
</pre></div>
<p>and for a build with shared libraries
</p><div class="example">
<pre class="example">./configure --target-os=mingw32 --enable-shared --disable-static --extra-cflags=-mno-cygwin --extra-libs=-mno-cygwin
</pre></div>
<p style="font-size: small;">
This document was generated using <a href="https://www.gnu.org/software/texinfo/"><em>makeinfo</em></a>.
</p>
</div>
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