1 \input texinfo @c -*- texinfo -*-
3 @settitle FFmpeg Documentation
6 @center @titlefont{FFmpeg Documentation}
13 FFmpeg is a very fast video and audio converter. It can also grab from
14 a live audio/video source.
16 The command line interface is designed to be intuitive, in the sense
17 that ffmpeg tries to figure out all the parameters, when
18 possible. You have usually to give only the target bitrate you want.
20 FFmpeg can also convert from any sample rate to any other, and resize
21 video on the fly with a high quality polyphase filter.
26 @section Video and Audio grabbing
28 FFmpeg can use a video4linux compatible video source and any Open Sound
35 Note that you must activate the right video source and channel before
36 launching ffmpeg. You can use any TV viewer such as xawtv
37 (@url{http://bytesex.org/xawtv/}) by Gerd Knorr which I find very
38 good. You must also set correctly the audio recording levels with a
41 @section Video and Audio file format conversion
43 * ffmpeg can use any supported file format and protocol as input:
47 * You can input from YUV files:
50 ffmpeg -i /tmp/test%d.Y /tmp/out.mpg
53 It will use the files:
55 /tmp/test0.Y, /tmp/test0.U, /tmp/test0.V,
56 /tmp/test1.Y, /tmp/test1.U, /tmp/test1.V, etc...
59 The Y files use twice the resolution of the U and V files. They are
60 raw files, without header. They can be generated by all decent video
61 decoders. You must specify the size of the image with the @option{-s} option
62 if ffmpeg cannot guess it.
64 * You can input from a RAW YUV420P file:
67 ffmpeg -i /tmp/test.yuv /tmp/out.avi
70 The RAW YUV420P is a file containing RAW YUV planar, for each frame first
71 come the Y plane followed by U and V planes, which are half vertical and
72 horizontal resolution.
74 * You can output to a RAW YUV420P file:
77 ffmpeg -i mydivx.avi -o hugefile.yuv
80 * You can set several input files and output files:
83 ffmpeg -i /tmp/a.wav -s 640x480 -i /tmp/a.yuv /tmp/a.mpg
86 Convert the audio file a.wav and the raw yuv video file a.yuv
89 * You can also do audio and video conversions at the same time:
92 ffmpeg -i /tmp/a.wav -ar 22050 /tmp/a.mp2
95 Convert the sample rate of a.wav to 22050 Hz and encode it to MPEG audio.
97 * You can encode to several formats at the same time and define a
98 mapping from input stream to output streams:
101 ffmpeg -i /tmp/a.wav -ab 64 /tmp/a.mp2 -ab 128 /tmp/b.mp2 -map 0:0 -map 0:0
104 Convert a.wav to a.mp2 at 64 kbits and b.mp2 at 128 kbits. '-map
105 file:index' specify which input stream is used for each output
106 stream, in the order of the definition of output streams.
108 * You can transcode decrypted VOBs
111 ffmpeg -i snatch_1.vob -f avi -vcodec mpeg4 -b 800 -g 300 -bf 2 -acodec mp3 -ab 128 snatch.avi
114 This is a typical DVD ripper example, input from a VOB file, output
115 to an AVI file with MPEG-4 video and MP3 audio, note that in this
116 command we use B frames so the MPEG-4 stream is DivX5 compatible, GOP
117 size is 300 that means an INTRA frame every 10 seconds for 29.97 fps
118 input video. Also the audio stream is MP3 encoded so you need LAME
119 support which is enabled using @code{--enable-mp3lame} when
120 configuring. The mapping is particularly useful for DVD transcoding
121 to get the desired audio language.
123 NOTE: to see the supported input formats, use @code{ffmpeg -formats}.
130 The generic syntax is:
133 @c man begin SYNOPSIS
134 ffmpeg [[options][@option{-i} @var{input_file}]]... @{[options] @var{output_file}@}...
137 @c man begin DESCRIPTION
138 If no input file is given, audio/video grabbing is done.
140 As a general rule, options are applied to the next specified
141 file. For example, if you give the @option{-b 64} option, it sets the video
142 bitrate of the next file. Format option may be needed for raw input
145 By default, ffmpeg tries to convert as losslessly as possible: it
146 uses the same audio and video parameter for the outputs as the one
147 specified for the inputs.
151 @section Main options
161 show available formats, codecs, protocols, ...
170 overwrite output files
173 set the recording time in seconds. @code{hh:mm:ss[.xxx]} syntax is also
182 @item -copyright string
185 @item -comment string
189 specify target file type ("vcd", "svcd" or "dvd"). All the format
190 options (bitrate, codecs, buffer sizes) are automatically set by this
191 option. You can just type:
194 ffmpeg -i myfile.avi -target vcd /tmp/vcd.mpg
198 activate high quality settings
202 @section Video Options
206 set the video bitrate in kbit/s (default = 200 kb/s)
208 set frame rate (default = 25)
210 set frame size. The format is @samp{WxH} (default 160x128). The
211 following abbreviations are recognized:
224 set aspect ratio (4:3, 16:9 or 1.3333, 1.7777)
226 set top crop band size (in pixels)
227 @item -cropbottom size
228 set bottom crop band size (in pixels)
230 set left crop band size (in pixels)
231 @item -cropright size
232 set right crop band size (in pixels)
234 disable video recording
236 set video bitrate tolerance (in kbit/s)
237 @item -maxrate bitrate
238 set max video bitrate tolerance (in kbit/s)
239 @item -minrate bitrate
240 set min video bitrate tolerance (in kbit/s)
242 set ratecontrol buffere size (in kbit)
244 force video codec to @var{codec}. Use the @code{copy} special value to
245 tell that the raw codec data must be copied as is.
247 use same video quality as source (implies VBR)
250 select the pass number (1 or 2). It is useful to do two pass
251 encoding. The statistics of the video are recorded in the first pass and
252 the video at the exact requested bit rate is generated in the second
255 @item -passlogfile file
256 select two pass log file name to @var{file}.
260 @section Advanced Video Options
264 set the group of picture size
266 use only intra frames
268 use fixed video quantiser scale (VBR)
270 min video quantiser scale (VBR)
272 max video quantiser scale (VBR)
274 max difference between the quantiser scale (VBR)
276 video quantiser scale blur (VBR)
277 @item -qcomp compression
278 video quantiser scale compression (VBR)
280 @item -rc_init_cplx complexity
281 initial complexity for 1-pass encoding
282 @item -b_qfactor factor
283 qp factor between p and b frames
284 @item -i_qfactor factor
285 qp factor between p and i frames
286 @item -b_qoffset offset
287 qp offset between p and b frames
288 @item -i_qoffset offset
289 qp offset between p and i frames
290 @item -rc_eq equation
291 set rate control equation (@pxref{FFmpeg formula
292 evaluator}). Default is @code{tex^qComp}.
293 @item -rc_override override
294 rate control override for specific intervals
296 set motion estimation method to @var{method}. Available methods are
297 (from lower to best quality):
300 Try just the (0, 0) vector.
307 exhaustive search (slow and marginally better than epzs)
311 set dct algorithm to @var{algo}. Available values are:
314 FF_DCT_AUTO (default)
327 @item -idct_algo algo
328 set idct algorithm to @var{algo}. Available values are:
331 FF_IDCT_AUTO (default)
355 set error resilience to @var{n}.
358 FF_ER_CAREFULL (default)
364 FF_ER_VERY_AGGRESSIVE
368 set error concealment to @var{bit_mask}. @var{bit_mask} is a bit mask of
369 the following values:
372 FF_EC_GUESS_MVS (default=enabled)
374 FF_EC_DEBLOCK (default=enabled)
378 use 'frames' B frames (supported for MPEG-1, MPEG-2 and MPEG-4)
383 FF_MB_DECISION_SIMPLE: use mb_cmp (cannot change it yet in ffmpeg)
385 FF_MB_DECISION_BITS: chooses the one which needs the fewest bits
387 FF_MB_DECISION_RD: rate distoration
391 use four motion vector by macroblock (only MPEG-4)
393 use data partitioning (only MPEG-4)
395 workaround not auto detected encoder bugs
396 @item -strict strictness
397 how strictly to follow the standarts
399 enable Advanced intra coding (h263+)
401 enable Unlimited Motion Vector (h263+)
406 force interlacing support in encoder (only MPEG-2 and MPEG-4). Use this option
407 if your input file is interlaced and if you want to keep the interlaced
408 format for minimum losses. The alternative is to deinterlace the input
409 stream with @option{-deinterlace}, but deinterlacing introduces more
412 calculate PSNR of compressed frames
414 dump video coding statistics to @file{vstats_HHMMSS.log}.
416 insert video processing @var{module}. @var{module} contains the module
417 name and its parameters separated by spaces.
420 @section Audio Options
424 set audio bitrate (in kbit/s)
426 set the audio sampling freq (default = 44100 Hz)
428 set the audio bitrate in kbit/s (default = 64)
430 set the number of audio channels (default = 1)
432 disable audio recording
434 force audio codec to @var{codec}. Use the @code{copy} special value to
435 tell that the raw codec data must be copied as is.
438 @section Audio/Video grab options
442 set video grab device (e.g. @file{/dev/video0})
444 set video grab channel (DV1394 only)
445 @item -tvstd standard
446 set television standard (NTSC, PAL (SECAM))
450 set audio device (e.g. @file{/dev/dsp})
453 @section Advanced options
456 @item -map file:stream
457 set input stream mapping
459 print specific debug info
461 add timings for benchmarking
463 dump each input packet
465 only use bit exact algorithms (for codec testing)
467 set packet size in bits
469 read input at native frame rate. Mainly used to simulate a grab device.
471 loop over the input stream. Currently it works only for image
472 streams. This option is used for ffserver automatic testing.
475 @node FFmpeg formula evaluator
476 @section FFmpeg formula evaluator
478 When evaluating a rate control string, FFmpeg uses an internal formula
481 The following binary operators are available: @code{+}, @code{-},
482 @code{*}, @code{/}, @code{^}.
484 The following unary operators are available: @code{+}, @code{-},
487 The following functions are available:
509 The following constants are available:
538 @settitle FFmpeg video converter
541 ffserver(1), ffplay(1) and the html documentation of @file{ffmpeg}.
552 The filename can be @file{-} to read from the standard input or to write
553 to the standard output.
555 ffmpeg handles also many protocols specified with the URL syntax.
557 Use 'ffmpeg -formats' to have a list of the supported protocols.
559 The protocol @code{http:} is currently used only to communicate with
560 ffserver (see the ffserver documentation). When ffmpeg will be a
561 video player it will also be used for streaming :-)
566 @item For streaming at very low bit rate application, use a low frame rate
567 and a small gop size. This is especially true for real video where
568 the Linux player does not seem to be very fast, so it can miss
569 frames. An example is:
572 ffmpeg -g 3 -r 3 -t 10 -b 50 -s qcif -f rv10 /tmp/b.rm
575 @item The parameter 'q' which is displayed while encoding is the current
576 quantizer. The value of 1 indicates that a very good quality could
577 be achieved. The value of 31 indicates the worst quality. If q=31
578 too often, it means that the encoder cannot compress enough to meet
579 your bit rate. You must either increase the bit rate, decrease the
580 frame rate or decrease the frame size.
582 @item If your computer is not fast enough, you can speed up the
583 compression at the expense of the compression ratio. You can use
584 '-me zero' to speed up motion estimation, and '-intra' to disable
585 completely motion estimation (you have only I frames, which means it
586 is about as good as JPEG compression).
588 @item To have very low bitrates in audio, reduce the sampling frequency
589 (down to 22050 kHz for mpeg audio, 22050 or 11025 for ac3).
591 @item To have a constant quality (but a variable bitrate), use the option
592 '-qscale n' when 'n' is between 1 (excellent quality) and 31 (worst
595 @item When converting video files, you can use the '-sameq' option which
596 uses in the encoder the same quality factor than in the decoder. It
597 allows to be almost lossless in encoding.
601 @chapter Supported File Formats and Codecs
603 You can use the @code{-formats} option to have an exhaustive list.
605 @section File Formats
607 FFmpeg supports the following file formats through the @code{libavformat}
610 @multitable @columnfractions .4 .1 .1
611 @item Supported File Format @tab Encoding @tab Decoding @tab Comments
612 @item MPEG audio @tab X @tab X
613 @item MPEG1 systems @tab X @tab X
614 @tab muxed audio and video
615 @item MPEG2 PS @tab X @tab X
616 @tab also known as @code{VOB} file
617 @item MPEG2 TS @tab @tab X
618 @tab also known as DVB Transport Stream
619 @item ASF@tab X @tab X
620 @item AVI@tab X @tab X
621 @item WAV@tab X @tab X
622 @item Macromedia Flash@tab X @tab X
623 @tab Only embedded audio is decoded
624 @item FLV @tab X @tab X
625 @tab Macromedia Flash video files
626 @item Real Audio and Video @tab X @tab X
627 @item Raw AC3 @tab X @tab X
628 @item Raw MJPEG @tab X @tab X
629 @item Raw MPEG video @tab X @tab X
630 @item Raw PCM8/16 bits, mulaw/Alaw@tab X @tab X
631 @item Raw CRI ADX audio @tab X @tab X
632 @item SUN AU format @tab X @tab X
633 @item NUT @tab X @tab X @tab NUT Open Container Format
634 @item Quicktime @tab X @tab X
635 @item MPEG4 @tab X @tab X
636 @tab MPEG4 is a variant of Quicktime
637 @item Raw MPEG4 video @tab X @tab X
638 @item DV @tab X @tab X
639 @item 4xm @tab @tab X
640 @tab 4X Technologies format, used in some games
641 @item Playstation STR @tab @tab X
642 @item Id RoQ @tab @tab X
643 @tab used in Quake III, Jedi Knight 2, other computer games
644 @item Interplay MVE @tab @tab X
645 @tab format used in various Interplay computer games
646 @item WC3 Movie @tab @tab X
647 @tab multimedia format used in Origin's Wing Commander III computer game
648 @item Sega FILM/CPK @tab @tab X
649 @tab used in many Sega Saturn console games
650 @item Westwood Studios VQA/AUD @tab @tab X
651 @tab Multimedia formats used in Westwood Studios games
652 @item Id Cinematic (.cin) @tab @tab X
653 @tab Used in Quake II
654 @item FLIC format @tab @tab X
656 @item Sierra VMD @tab @tab X
657 @tab used in Sierra CD-ROM games
660 @code{X} means that the encoding (resp. decoding) is supported.
662 @section Image Formats
664 FFmpeg can read and write images for each frame of a video sequence. The
665 following image formats are supported:
667 @multitable @columnfractions .4 .1 .1
668 @item Supported Image Format @tab Encoding @tab Decoding @tab Comments
669 @item PGM, PPM @tab X @tab X
670 @item PAM @tab X @tab X @tab PAM is a PNM extension with alpha support
671 @item PGMYUV @tab X @tab X @tab PGM with U and V components in YUV 4:2:0
672 @item JPEG @tab X @tab X @tab Progressive JPEG is not supported
673 @item .Y.U.V @tab X @tab X @tab One raw file per component
674 @item Animated GIF @tab X @tab X @tab Only uncompressed GIFs are generated
675 @item PNG @tab X @tab X @tab 2 bit and 4 bit/pixel not supported yet
678 @code{X} means that the encoding (resp. decoding) is supported.
680 @section Video Codecs
682 @multitable @columnfractions .4 .1 .1 .7
683 @item Supported Codec @tab Encoding @tab Decoding @tab Comments
684 @item MPEG1 video @tab X @tab X
685 @item MPEG2 video @tab X @tab X
686 @item MPEG4 @tab X @tab X @tab Also known as DIVX4/5
687 @item MSMPEG4 V1 @tab X @tab X
688 @item MSMPEG4 V2 @tab X @tab X
689 @item MSMPEG4 V3 @tab X @tab X @tab Also known as DIVX3
690 @item WMV7 @tab X @tab X
691 @item WMV8 @tab X @tab X @tab Not completely working
692 @item H263(+) @tab X @tab X @tab Also known as Real Video 1.0
693 @item MJPEG @tab X @tab X
694 @item Lossless MJPEG @tab X @tab X
695 @item Apple MJPEG-B @tab @tab X
696 @item Sunplus MJPEG @tab @tab X @tab fourcc: SP5X
697 @item DV @tab X @tab X
698 @item Huff YUV @tab X @tab X
699 @item FFmpeg Video 1 @tab X @tab X @tab Lossless codec (fourcc: FFV1)
700 @item Asus v1 @tab X @tab X @tab fourcc: ASV1
701 @item Asus v2 @tab X @tab X @tab fourcc: ASV2
702 @item Creative YUV @tab @tab X @tab fourcc: CYUV
703 @item H.264 @tab @tab X
704 @item Sorenson Video 1 @tab @tab X @tab fourcc: SVQ1
705 @item Sorenson Video 3 @tab @tab X @tab fourcc: SVQ3
706 @item On2 VP3 @tab @tab X @tab still experimental
707 @item Theora @tab @tab X @tab still experimental
708 @item Intel Indeo 3 @tab @tab X @tab only works on i386 right now
709 @item FLV @tab X @tab X @tab Flash H263 variant
710 @item ATI VCR1 @tab @tab X @tab fourcc: VCR1
711 @item ATI VCR2 @tab @tab X @tab fourcc: VCR2
712 @item Cirrus Logic AccuPak @tab @tab X @tab fourcc: CLJR
713 @item 4X Video @tab @tab X @tab used in certain computer games
714 @item Sony Playstation MDEC @tab @tab X
715 @item Id RoQ @tab @tab X @tab used in Quake III, Jedi Knight 2, other computer games
716 @item Xan/WC3 @tab @tab X @tab used in Wing Commander III .MVE files
717 @item Interplay Video @tab @tab X @tab used in Interplay .MVE files
718 @item Apple Graphics @tab @tab X @tab fourcc: 'smc '
719 @item Apple Video @tab @tab X @tab fourcc: rpza
720 @item Cinepak @tab @tab X
721 @item Microsoft RLE @tab @tab X
722 @item Microsoft Video-1 @tab @tab X
723 @item Westwood VQA @tab @tab X
724 @item Id Cinematic Video @tab @tab X @tab used in Quake II
725 @item Planar RGB @tab @tab X @tab fourcc: 8BPS
726 @item FLIC video @tab @tab X
727 @item Duck TrueMotion v1 @tab @tab X @tab fourcc: DUCK
728 @item VMD Video @tab @tab X @tab used in Sierra VMD files
731 @code{X} means that the encoding (resp. decoding) is supported.
733 Check at @url{http://www.mplayerhq.hu/~michael/codec-features.html} to
734 get a precise comparison of FFmpeg MPEG4 codec compared to the other
737 @section Audio Codecs
739 @multitable @columnfractions .4 .1 .1 .1 .7
740 @item Supported Codec @tab Encoding @tab Decoding @tab Comments
741 @item MPEG audio layer 2 @tab IX @tab IX
742 @item MPEG audio layer 1/3 @tab IX @tab IX
743 @tab MP3 encoding is supported through the external library LAME
744 @item AC3 @tab IX @tab X
745 @tab liba52 is used internally for decoding
746 @item Vorbis @tab X @tab X
747 @tab supported through the external library libvorbis
748 @item WMA V1/V2 @tab @tab X
749 @item Microsoft ADPCM @tab @tab X
750 @item MS IMA ADPCM @tab X @tab X
751 @item QT IMA ADPCM @tab @tab X
752 @item 4X IMA ADPCM @tab @tab X
753 @item Duck DK3 IMA ADPCM @tab @tab X
754 @tab used in some Sega Saturn console games
755 @item Duck DK4 IMA ADPCM @tab @tab X
756 @tab used in some Sega Saturn console games
757 @item Westwood Studios IMA ADPCM @tab @tab X
758 @tab used in Westwood Studios games like Command and Conquer
759 @item CD-ROM XA ADPCM @tab @tab X
760 @item CRI ADX ADPCM @tab X @tab X
761 @tab used in Sega Dreamcast games
762 @item RA144 @tab @tab X
763 @tab Real 14400 bit/s codec
764 @item RA288 @tab @tab X
765 @tab Real 28800 bit/s codec
766 @item AMR-NB @tab X @tab X
767 @tab supported through an external library
768 @item AMR-WB @tab X @tab X
769 @tab supported through an external library
770 @item DV audio @tab @tab X
771 @item Id RoQ DPCM @tab @tab X
772 @tab used in Quake III, Jedi Knight 2, other computer games
773 @item Interplay MVE DPCM @tab @tab X
774 @tab used in various Interplay computer games
775 @item Xan DPCM @tab @tab X
776 @tab used in Origin's Wing Commander IV AVI files
777 @item Apple MACE 3 @tab @tab X
778 @item Apple MACE 6 @tab @tab X
781 @code{X} means that the encoding (resp. decoding) is supported.
783 @code{I} means that an integer only version is available too (ensures highest
784 performances on systems without hardware floating point support).
786 @chapter Platform Specific information
790 ffmpeg should be compiled with at least GCC 2.95.3. GCC 3.2 is the
791 preferred compiler now for ffmpeg. All future optimizations will depend on
792 features only found in GCC 3.2.
798 @subsection Native Windows compilation
801 @item Install the current versions of MSYS and MinGW from
802 @url{http://www.mingw.org/}. You can find detailed installation
803 instructions in the download section and the FAQ.
805 @item If you want to test the FFmpeg Simple Media Player, also download
806 the MinGW development library of SDL 1.2.x
807 (@file{SDL-devel-1.2.x-mingw32.tar.gz}) from
808 @url{http://www.libsdl.org}. Unpack it in a temporary place, and
809 unpack the archive @file{i386-mingw32msvc.tar.gz} in the MinGW tool
810 directory. Edit the @file{sdl-config} script so that it gives the
811 correct SDL directory when invoked.
813 @item Extract the current version of FFmpeg (the latest release version or the current CVS snapshot whichever is recommended).
815 @item Start the MSYS shell (file @file{msys.bat}).
817 @item Change to the FFMPEG directory and follow
818 the instructions of how to compile ffmpeg (file
819 @file{INSTALL}). Usually, launching @file{./configure} and @file{make}
820 suffices. If you have problems using SDL, verify that
821 @file{sdl-config} can be launched from the MSYS command line.
823 @item You can install FFmpeg in @file{Program Files/FFmpeg} by typing @file{make install}. Don't forget to copy @file{SDL.dll} at the place you launch
831 @item The target @file{make wininstaller} can be used to create a
832 Nullsoft based Windows installer for FFmpeg and FFplay. @file{SDL.dll}
833 must be copied in the ffmpeg directory in order to build the
836 @item By using @code{./configure --enable-shared} when configuring ffmpeg,
837 you can build @file{avcodec.dll} and @file{avformat.dll}. With
838 @code{make install} you install the FFmpeg DLLs and the associated
839 headers in @file{Program Files/FFmpeg}.
841 @item Visual C++ compatibility: if you used @code{./configure --enable-shared}
842 when configuring FFmpeg, then FFmpeg tries to use the Microsoft Visual
843 C++ @code{lib} tool to build @code{avcodec.lib} and
844 @code{avformat.lib}. With these libraries, you can link your Visual C++
845 code directly with the FFmpeg DLLs.
849 @subsection Cross compilation for Windows with Linux
851 You must use the MinGW cross compilation tools available at
852 @url{http://www.mingw.org/}.
854 Then configure ffmpeg with the following options:
856 ./configure --enable-mingw32 --cross-prefix=i386-mingw32msvc-
858 (you can change the cross-prefix according to the prefix choosen for the
861 Then you can easily test ffmpeg with wine
862 (@url{http://www.winehq.com/}).
868 The configure script should guess the configuration itself.
869 Networking support is currently not finished.
870 errno issues fixed by Andrew Bachmann.
874 François Revol - revol at free dot fr - April 2002
876 The configure script should guess the configuration itself,
877 however I still didn't tested building on net_server version of BeOS.
879 ffserver is broken (needs poll() implementation).
881 There is still issues with errno codes, which are negative in BeOs, and
882 that ffmpeg negates when returning. This ends up turning errors into
883 valid results, then crashes.
886 @chapter Developers Guide
890 @item libavcodec is the library containing the codecs (both encoding and
891 decoding). See @file{libavcodec/apiexample.c} to see how to use it.
893 @item libavformat is the library containing the file formats handling (mux and
894 demux code for several formats). See @file{ffplay.c} to use it in a
895 player. See @file{output_example.c} to use it to generate audio or video
900 @section Integrating libavcodec or libavformat in your program
902 You can integrate all the source code of the libraries to link them
903 statically to avoid any version problem. All you need is to provide a
904 'config.mak' and a 'config.h' in the parent directory. See the defines
905 generated by ./configure to understand what is needed.
907 You can use libavcodec or libavformat in your commercial program, but
908 @emph{any patch you make must be published}. The best way to proceed is
909 to send your patches to the ffmpeg mailing list.
911 @section Coding Rules
913 ffmpeg is programmed in ANSI C language. GCC extensions are
914 tolerated. Indent size is 4. The TAB character should not be used.
916 The presentation is the one specified by 'indent -i4 -kr'.
918 Main priority in ffmpeg is simplicity and small code size (=less
921 Comments: for functions visible from other modules, use the JavaDoc
922 format (see examples in @file{libav/utils.c}) so that a documentation
923 can be generated automatically.
925 @section Submitting patches
927 When you submit your patch, try to send a unified diff (diff '-up'
928 option). I cannot read other diffs :-)
930 Run the regression tests before submitting a patch so that you can
931 verify that there are no big problems.
933 Patches should be posted as base64 encoded attachments (or any other
934 encoding which ensures that the patch wont be trashed during
935 transmission) to the ffmpeg-devel mailinglist, see
936 @url{http://lists.sourceforge.net/lists/listinfo/ffmpeg-devel}
938 It also helps quite a bit if you tell us what the patch does (for example
939 'replaces lrint by lrintf') , and why (for example '*bsd isnt c99 compliant
942 @section Regression tests
944 Before submitting a patch (or committing with CVS), you should at least
945 test that you did not break anything.
947 The regression test build a synthetic video stream and a synthetic
948 audio stream. Then these are encoded then decoded with all codecs or
949 formats. The CRC (or MD5) of each generated file is recorded in a
950 result file. Then a 'diff' is launched with the reference results and
953 The regression test then goes on to test the ffserver code with a
954 limited set of streams. It is important that this step runs correctly
957 Run 'make test' to test all the codecs.
959 Run 'make fulltest' to test all the codecs, formats and ffserver.
961 [Of course, some patches may change the regression tests results. In
962 this case, the regression tests reference results shall be modified