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\input texinfo @c -*- texinfo -*-
@settitle General Documentation
@titlepage
@sp 7
@center @titlefont{General Documentation}
@sp 3
@end titlepage
@chapter external libraries
FFmpeg can be hooked up with a number of external libraries to add support
for more formats. None of them are used by default, their use has to be
explicitly requested by passing the appropriate flags to @file{./configure}.
@section AMR
AMR comes in two different flavors, wideband and narrowband. FFmpeg can make
use of the AMR wideband (floating-point mode) and the AMR narrowband
(floating-point mode) reference decoders and encoders.
Go to @url{http://www.penguin.cz/~utx/amr} and follow the instructions for
installing the libraries. Then pass @code{--enable-libamr-nb} and/or
@code{--enable-libamr-wb} to configure to enable the libraries.
Note that libamr is copyrighted without any sort of license grant. This means
that you can use it if you legally obtained it but you are not allowed to
redistribute it in any way. @strong{Any FFmpeg binaries with libamr support
you create are non-free and unredistributable!}
@chapter Supported File Formats and Codecs
You can use the @code{-formats} option to have an exhaustive list.
@section File Formats
FFmpeg supports the following file formats through the @code{libavformat}
library:
@multitable @columnfractions .4 .1 .1 .4
@item Name @tab Encoding @tab Decoding @tab Comments
@tab 4X Technologies format, used in some games.
@item ADTS AAC audio @tab X @tab X
@item American Laser Games MM @tab @tab X
@tab Multimedia format used in games like Mad Dog McCree.
@item ASF @tab X @tab X
@item AVI @tab X @tab X
@item AVM2 (Flash 9) @tab X @tab X
@tab Only embedded audio is decoded.
@tab Multimedia format used by the Creature Shock game.
@item Bethsoft VID @tab @tab X
@tab Used in some games from Bethesda Softworks.
@item BFI @tab @tab X
@tab Brute Force & Ignorance, used in Flash Traffic: City of Angels.
@tab Used in the game Cyberia from Interplay.
@tab Multimedia format used by Delphine Software games.
@item Creative VOC @tab X @tab X
@tab Created for the Sound Blaster Pro.
@item CRYO APC @tab @tab X
@tab Audio format used in some games by CRYO Interactive Entertainment.
@item DV @tab X @tab X
@item DXA @tab @tab X
@tab This format is used in the non-Windows version of the Feeble Files
game and different game cutscenes repacked for use with ScummVM.
@item Electronic Arts Multimedia @tab @tab X
@tab Used in various EA games; files have extensions like WVE and UV2.
@tab Macromedia Flash video files
@item FunCom ISS @tab @tab X
@tab Audio format used in various games from FunCom like The Longest Journey.
@tab General eXchange Format SMPTE 360M, used by Thomson Grass Valley
@tab Used in Quake III, Jedi Knight 2, other computer games.
@item Interplay MVE @tab @tab X
@tab Format used in various Interplay computer games.
@tab Used by Linux Media Labs MPEG-4 PCI boards
@item MAXIS EA XA @tab @tab X
@tab Used in Sim City 3000; file extension .xa.
@item Motion Pixels MVI @tab @tab X
@item MPEG audio @tab X @tab X
@item MPEG-1 systems @tab X @tab X
@item MPEG-2 PS @tab X @tab X
@tab also known as @code{VOB} file
@item MPEG-2 TS @tab @tab X
@tab also known as DVB Transport Stream
@tab MPEG-4 is a variant of QuickTime.
@item MSN TCP webcam @tab @tab X
@tab Used by MSN Messenger webcam streams.
@tab Material eXchange Format SMPTE 377M, used by D-Cinema, broadcast industry.
@item NC @tab @tab X
@tab NC (AVIP NC4600) cameras streams.
@tab Audio format used in Sony Sonic Stage and Sony Vegas.
@tab Used by TechnoTrend DVB PCI boards.
@item raw AC-3 @tab X @tab X
@item raw CRI ADX audio @tab X @tab X
@item raw MJPEG @tab X @tab X
@item raw MPEG video @tab X @tab X
@item raw MPEG-4 video @tab X @tab X
@item raw PCM 8/16/32 bits, 32/64-bit floating point, mu-law/A-law @tab X @tab X
@item R3D REDCODE @tab @tab X
@tab File format used by RED Digital cameras, contains JPEG 2000 frames and PCM audio.
@tab Audio and video format used in some games by Entertainment Software Partners.
@item Sega FILM/CPK @tab @tab X
@tab Used in many Sega Saturn console games.
@item SEQ @tab @tab X
@tab Tiertex .seq files used in the DOS CD-ROM version of the game Flashback.
@item Sierra Online @tab @tab X
@tab .sol files used in Sierra Online games.
@item Sierra VMD @tab @tab X
@tab Used in Sierra CD-ROM games.
@item SIFF @tab @tab X
@tab Audio and video format used in some games by Beam Software.
@tab Multimedia format used by many games.
@tab Used on the Nintendo GameCube.
@item WAV @tab X @tab X
@item WC3 Movie @tab @tab X
@tab Multimedia format used in Origin's Wing Commander III computer game.
@item Westwood Studios VQA/AUD @tab @tab X
@tab Multimedia formats used in Westwood Studios games.
@end multitable
@code{X} means that encoding (resp. decoding) is supported.
@section Image Formats
FFmpeg can read and write images for each frame of a video sequence. The
following image formats are supported:
@multitable @columnfractions .4 .1 .1 .4
@item Name @tab Encoding @tab Decoding @tab Comments
@item .Y.U.V @tab X @tab X @tab one raw file per component
@item animated GIF @tab X @tab X @tab Only uncompressed GIFs are generated.
@item JPEG @tab X @tab X @tab Progressive JPEG is not supported.
@item JPEG 2000 @tab @tab E @tab decoding supported through external library libopenjpeg
@item PAM @tab X @tab X @tab PAM is a PNM extension with alpha support.
@item PCX @tab @tab X @tab PC Paintbrush
@item PGM, PPM @tab X @tab X
@item PGMYUV @tab X @tab X @tab PGM with U and V components in YUV 4:2:0
@item PNG @tab X @tab X @tab 2/4 bpp not supported yet
@item PTX @tab @tab X @tab V.Flash PTX format
@item RAS @tab @tab X @tab Sun Rasterfile
@item SGI @tab X @tab X @tab SGI RGB image format
@item Targa @tab @tab X @tab Targa (.TGA) image format
@item TIFF @tab X @tab X @tab YUV, JPEG and some extension is not supported yet.
@end multitable
@code{X} means that encoding (resp. decoding) is supported.
@code{E} means that support is provided through an external library.
@section Video Codecs
@multitable @columnfractions .4 .1 .1 .4
@item Name @tab Encoding @tab Decoding @tab Comments
@tab Used in certain computer games.
@item American Laser Games Video @tab @tab X
@tab Used in games like Mad Dog McCree.
@tab Used in Chinese MP3 players.
@item Apple Animation @tab X @tab X
@item Apple Graphics @tab @tab X
@item Apple MJPEG-B @tab @tab X
@item Apple QuickDraw @tab @tab X
@tab Video encoding used by the Creature Shock game.
@tab Used in some games from Bethesda Softworks.
@tab Codec used in Cyberia game.
@tab Codec used in Delphine Software games.
@item Cinepak @tab @tab X
@item Cirrus Logic AccuPak @tab @tab X
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@item Dirac @tab E @tab E
@tab supported through external libdirac/libschroedinger libraries
@item Duck TrueMotion v1 @tab @tab X
@item Duck TrueMotion v2 @tab @tab X
@item DV @tab X @tab X
@item DXA Video @tab @tab X
@tab Codec originally used in Feeble Files game.
@item Electronic Arts CMV @tab @tab X
@item FFmpeg Video 1 @tab X @tab X
@tab experimental lossless codec (fourcc: FFV1)
@item Flash Screen Video @tab X @tab X
@item FLIC video @tab @tab X
@item FLV @tab X @tab X
@tab Sorenson H.263 used in Flash
@item Fraps FPS1 @tab @tab X
@item H.261 @tab X @tab X
@item H.263(+) @tab X @tab X
@tab also known as RealVideo 1.0
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@item H.264 @tab E @tab X
@tab encoding supported through external library libx264
@item HuffYUV @tab X @tab X
@item IBM Ultimotion @tab @tab X
@item id Cinematic video @tab @tab X
@tab Used in Quake III, Jedi Knight 2, other computer games.
@item Intel Indeo 3 @tab @tab X
@item Interplay Video @tab @tab X
@tab Used in Interplay .MVE files.
@tab fourcc: MJLS, lossless and near-lossless is supported.
@tab Codec used in Worms games.
@item LOCO @tab @tab X
@item lossless MJPEG @tab X @tab X
@item Microsoft RLE @tab @tab X
@item Microsoft Video-1 @tab @tab X
@item Mimic @tab @tab X
@tab Used in MSN Messenger Webcam streams.
@item Motion Pixels Video @tab @tab X
@item MPEG-1 @tab X @tab X
@item MPEG-2 @tab X @tab X
@item MPEG-4 @tab X @tab X
@item MSMPEG4 V1 @tab X @tab X
@item MSMPEG4 V2 @tab X @tab X
@item MSMPEG4 V3 @tab X @tab X
@item RealVideo 1.0 @tab X @tab X
@item RealVideo 2.0 @tab X @tab X
@item RealVideo 3.0 @tab @tab X
@tab still far from ideal
@item Renderware TXD @tab @tab X
@tab Texture dictionaries used by the Renderware Engine.
@tab Video encoding used in NuppelVideo files.
@item Smacker video @tab @tab X
@tab Video encoding used in Smacker.
@tab experimental wavelet codec (fourcc: SNOW)
@item Sony PlayStation MDEC @tab @tab X
@item Sorenson Video 1 @tab X @tab X
@item Sorenson Video 3 @tab @tab X
@item Sunplus MJPEG @tab @tab X
@item TechSmith Camtasia @tab @tab X
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@item Theora @tab E @tab X
@tab encoding supported through external library libtheora
@tab Used on the Nintendo GameCube.
@item Tiertex Seq video @tab @tab X
@tab Codec used in DOS CD-ROM FlashBack game.
@item VC-1 @tab @tab X
@item VMD Video @tab @tab X
@tab Codec used in videos captured by VMware.
@item Westwood VQA @tab @tab X
@item Winnov WNV1 @tab @tab X
@item WMV7 @tab X @tab X
@item WMV8 @tab X @tab X
@item WMV9 @tab @tab X
@tab Used in Wing Commander III .MVE files.
@tab part of LCL, encoder experimental
@tab Encoder works only in PAL8.
@end multitable
@code{X} means that encoding (resp. decoding) is supported.
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@code{E} means that support is provided through an external library.
@section Audio Codecs
@multitable @columnfractions .4 .1 .1 .4
@item Name @tab Encoding @tab Decoding @tab Comments
@item 4X IMA ADPCM @tab @tab X
@item 8SVX audio @tab @tab X
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@item AAC @tab E @tab X
@tab encoding supported through external library libfaac
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@item AMR-NB @tab E @tab E
@tab supported through external library libamrnb
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@item AMR-WB @tab E @tab E
@tab supported through external library libamrwb
@item AMV IMA ADPCM @tab @tab X
@item Apple lossless audio @tab X @tab X
@item Apple MACE 3 @tab @tab X
@item Apple MACE 6 @tab @tab X
@item ATRAC 3 @tab @tab X
@item CD-ROM XA ADPCM @tab @tab X
@tab Codec used in Delphine Software International games.
@item Creative ADPCM @tab @tab X
@tab 16 -> 4, 8 -> 4, 8 -> 3, 8 -> 2
@item CRI ADX ADPCM @tab X @tab X
@tab Used in Sega Dreamcast games.
@item DSP Group TrueSpeech @tab @tab X
@item DTS Coherent Audio @tab @tab X
@item Duck DK3 IMA ADPCM @tab @tab X
@tab Used in some Sega Saturn console games.
@item Duck DK4 IMA ADPCM @tab @tab X
@tab Used in some Sega Saturn console games.
@item DV audio @tab @tab X
@item Electronic Arts ADPCM @tab @tab X
@tab Used in various EA titles.
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@item FLAC lossless audio @tab IX @tab X
@item G.726 ADPCM @tab X @tab X
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@item GSM @tab E @tab E
@tab supported through external library libgsm
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@item GSM_MS @tab E @tab E
@tab supported through external library libgsm
@item id RoQ DPCM @tab X @tab X
@tab Used in Quake III, Jedi Knight 2, other computer games.
@item Intel Music Coder @tab @tab X
@item Interplay MVE DPCM @tab @tab X
@tab Used in various Interplay computer games.
@item ISS IMA ADPCM @tab @tab X
@tab Used in FunCom games.
@item MAXIS EA ADPCM @tab @tab X
@item Microsoft ADPCM @tab X @tab X
@item MLP/TrueHD @tab @tab X
@tab Used in DVD-Audio and Blu-Ray discs.
@item Monkey's Audio @tab @tab X
@tab Only versions 3.97-3.99 are supported.
@item MPEG audio layer 3 @tab E @tab IX
@tab encoding supported through external library LAME
@item MPEG audio layer 2 @tab IX @tab IX
@item MS IMA ADPCM @tab X @tab X
@item Musepack @tab @tab X
@tab SV7 and SV8 are supported.
@item Nellymoser ASAO @tab X @tab X
@item QCELP / PureVoice @tab @tab X
@tab There are still some distortions.
@item QT IMA ADPCM @tab X @tab X
@item RA144 @tab @tab X
@tab All versions except 5.1 are supported.
@item Sierra Online DPCM @tab @tab X
@tab Used in Sierra Online game audio files.
@item Smacker audio @tab @tab X
@item SMJPEG IMA ADPCM @tab @tab X
@tab Used in certain Loki game ports.
@item Sonic @tab X @tab X
@tab experimental codec
@item Sonic lossless @tab X @tab X
@tab experimental codec
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@item Speex @tab @tab E
@tab supported through external library libspeex
@tab Used on the Nintendo GameCube.
@item True Audio (TTA) @tab @tab X
@item Vorbis @tab X @tab X
@item Westwood Studios IMA ADPCM @tab @tab X
@tab Used in Westwood Studios games like Command and Conquer.
@tab Used in Origin's Wing Commander IV AVI files.
@end multitable
@code{X} means that encoding (resp. decoding) is supported.
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@code{E} means that support is provided through an external library.
@code{I} means that an integer-only version is available, too (ensures high
performance on systems without hardware floating point support).
@multitable @columnfractions .4 .1 .1 .1 .1 .1
@item Name @tab Muxing @tab Demuxing @tab Encoding @tab Decoding @tab Rendering
@item ASS/SSA @tab X @tab X
@item DVB @tab X @tab X @tab X @tab X @tab X
@item DVD @tab X @tab X @tab X @tab X @tab X
@item XSUB @tab @tab @tab @tab X @tab
@end multitable
@code{X} means that the feature is supported.
@chapter Platform Specific information
@section BSD
BSD make will not build FFmpeg, you need to install and use GNU Make
(@file{gmake}).
@section Windows
To get help and instructions for building FFmpeg under Windows, check out
the FFmpeg Windows Help Forum at
@url{http://ffmpeg.arrozcru.org/}.
@subsection Native Windows compilation
FFmpeg can be built to run natively on Windows using the MinGW tools. Install
the latest versions of MSYS and MinGW from @url{http://www.mingw.org/}.
You can find detailed installation
instructions in the download section and the FAQ.
FFmpeg does not build out-of-the-box with the packages the automated MinGW
installer provides. It also requires coreutils to be installed and many other
packages updated to the latest version. The minimum version for some packages
are listed below:
@itemize
@item bash 3.1
@item msys-make 3.81-2 (note: not mingw32-make)
@item w32api 3.13
@item mingw-runtime 3.15
@end itemize
You will also need to pass @code{-fno-common} to the compiler to work around
a GCC bug (see @url{http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37216}).
Within the MSYS shell, configure and make with:
./configure --enable-memalign-hack --extra-cflags=-fno-common
make
make install
@end example
This will install @file{ffmpeg.exe} along with many other development files
to @file{/usr/local}. You may specify another install path using the
@code{--prefix} option in @file{configure}.
@item In order to compile vhooks, you must have a POSIX-compliant libdl in
your MinGW system. Get dlfcn-win32 from
@url{http://code.google.com/p/dlfcn-win32}.
@item In order to compile FFplay, you must have the MinGW development library
of SDL. Get it from @url{http://www.libsdl.org}.
Edit the @file{bin/sdl-config} script so that it points to the correct prefix
where SDL was installed. Verify that @file{sdl-config} can be launched from
the MSYS command line.
@item By using @code{./configure --enable-shared} when configuring FFmpeg,
you can build libavutil, libavcodec and libavformat as DLLs.
@end itemize
@subsection Microsoft Visual C++ compatibility
As stated in the FAQ, FFmpeg will not compile under MSVC++. However, if you
want to use the libav* libraries in your own applications, you can still
compile those applications using MSVC++. But the libav* libraries you link
to @emph{must} be built with MinGW. However, you will not be able to debug
inside the libav* libraries, since MSVC++ does not recognize the debug
symbols generated by GCC.
We strongly recommend you to move over from MSVC++ to MinGW tools.
This description of how to use the FFmpeg libraries with MSVC++ is based on
Microsoft Visual C++ 2005 Express Edition. If you have a different version,
you might have to modify the procedures slightly.
@subsubsection Using static libraries
Assuming you have just built and installed FFmpeg in @file{/usr/local}.
@enumerate
@item Create a new console application ("File / New / Project") and then
select "Win32 Console Application". On the appropriate page of the
Application Wizard, uncheck the "Precompiled headers" option.
@item Write the source code for your application, or, for testing, just
copy the code from an existing sample application into the source file
that MSVC++ has already created for you. For example, you can copy
@file{output_example.c} from the FFmpeg distribution.
@item Open the "Project / Properties" dialog box. In the "Configuration"
combo box, select "All Configurations" so that the changes you make will
affect both debug and release builds. In the tree view on the left hand
side, select "C/C++ / General", then edit the "Additional Include
Directories" setting to contain the path where the FFmpeg includes were
installed (i.e. @file{c:\msys\1.0\local\include}).
Do not add MinGW's include directory here, or the include files will
conflict with MSVC's.
@item Still in the "Project / Properties" dialog box, select
"Linker / General" from the tree view and edit the
"Additional Library Directories" setting to contain the @file{lib}
directory where FFmpeg was installed (i.e. @file{c:\msys\1.0\local\lib}),
the directory where MinGW libs are installed (i.e. @file{c:\mingw\lib}),
and the directory where MinGW's GCC libs are installed
(i.e. @file{C:\mingw\lib\gcc\mingw32\4.2.1-sjlj}). Then select
"Linker / Input" from the tree view, and add the files @file{libavformat.a},
@file{libavcodec.a}, @file{libavutil.a}, @file{libmingwex.a},
@file{libgcc.a}, and any other libraries you used (i.e. @file{libz.a})
to the end of "Additional Dependencies".
@item Now, select "C/C++ / Code Generation" from the tree view. Select
"Debug" in the "Configuration" combo box. Make sure that "Runtime
Library" is set to "Multi-threaded Debug DLL". Then, select "Release" in
the "Configuration" combo box and make sure that "Runtime Library" is
set to "Multi-threaded DLL".
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@item Click "OK" to close the "Project / Properties" dialog box.
@item MSVC++ lacks some C99 header files that are fundamental for FFmpeg.
Get msinttypes from @url{http://code.google.com/p/msinttypes/downloads/list}
and install it in MSVC++'s include directory
(i.e. @file{C:\Program Files\Microsoft Visual Studio 8\VC\include}).
@item MSVC++ also does not understand the @code{inline} keyword used by
FFmpeg, so you must add this line before @code{#include}ing libav*:
@example
#define inline _inline
@end example
@item Build your application, everything should work.
@end enumerate
@subsubsection Using shared libraries
This is how to create DLL and LIB files that are compatible with MSVC++:
@enumerate
@item Add a call to @file{vcvars32.bat} (which sets up the environment
variables for the Visual C++ tools) as the first line of @file{msys.bat}.
The standard location for @file{vcvars32.bat} is
@file{C:\Program Files\Microsoft Visual Studio 8\VC\bin\vcvars32.bat},
and the standard location for @file{msys.bat} is @file{C:\msys\1.0\msys.bat}.
If this corresponds to your setup, add the following line as the first line
of @file{msys.bat}:
@example
call "C:\Program Files\Microsoft Visual Studio 8\VC\bin\vcvars32.bat"
@end example
Alternatively, you may start the @file{Visual Studio 2005 Command Prompt},
and run @file{c:\msys\1.0\msys.bat} from there.
@item Within the MSYS shell, run @code{lib.exe}. If you get a help message
from @file{Microsoft (R) Library Manager}, this means your environment
variables are set up correctly, the @file{Microsoft (R) Library Manager}
is on the path and will be used by FFmpeg to create
MSVC++-compatible import libraries.
@item Build FFmpeg with
@example
./configure --enable-shared --enable-memalign-hack
make
make install
@end example
Your install path (@file{/usr/local/} by default) should now have the
necessary DLL and LIB files under the @file{bin} directory.
@end enumerate
To use those files with MSVC++, do the same as you would do with
the static libraries, as described above. But in Step 4,
you should only need to add the directory where the LIB files are installed
(i.e. @file{c:\msys\usr\local\bin}). This is not a typo, the LIB files are
installed in the @file{bin} directory. And instead of adding @file{libxx.a}
files, you should add @file{avcodec.lib}, @file{avformat.lib}, and
@file{avutil.lib}. There should be no need for @file{libmingwex.a},
@file{libgcc.a}, and @file{wsock32.lib}, nor any other external library
statically linked into the DLLs. The @file{bin} directory contains a bunch
of DLL files, but the ones that are actually used to run your application
are the ones with a major version number in their filenames
(i.e. @file{avcodec-51.dll}).
@subsection Cross compilation for Windows with Linux
You must use the MinGW cross compilation tools available at
@url{http://www.mingw.org/}.
Then configure FFmpeg with the following options:
@example
./configure --target-os=mingw32 --cross-prefix=i386-mingw32msvc-
@end example
(you can change the cross-prefix according to the prefix chosen for the
MinGW tools).
Then you can easily test FFmpeg with Wine
(@url{http://www.winehq.com/}).
@subsection Compilation under Cygwin
The main issue with the 1.5.x Cygwin versions is that newlib, its C library,
does not contain llrint(). You need to upgrade to the unstable 1.7.x versions,
or leverage the implementation in MinGW (as explained below).
Just install your Cygwin with all the "Base" packages, plus the
following "Devel" ones:
@example
binutils, gcc-core, make, subversion, mingw-runtime, diffutils
@end example
The experimental gcc4 package is still buggy, hence please
use the official gcc 3.4.4 or a 4.2.x compiled from source by yourself.
Install the current binutils-20080624-2 as they work fine (the old
binutils-20060709-1 proved buggy on shared builds).
Then create a small library that just contains llrint():
@example
ar x /usr/lib/mingw/libmingwex.a llrint.o
ar cq /usr/local/lib/libllrint.a llrint.o
@end example
Then run
@example
./configure --enable-static --disable-shared --extra-ldflags='-L /usr/local/lib' --extra-libs='-l llrint'
@end example
to make a static build or
@example
./configure --enable-shared --disable-static --extra-ldflags='-L /usr/local/lib' --extra-libs='-l llrint'
@end example
to build shared libraries.
If you want to build FFmpeg with additional libraries, download Cygwin
"Devel" packages for Ogg and Vorbis from any Cygwin packages repository:
@example
libogg-devel, libvorbis-devel
@end example
These library packages are only available from Cygwin Ports
(@url{http://sourceware.org/cygwinports/}) :
@example
yasm, libSDL-devel, libdirac-devel, libfaac-devel, libfaad-devel, libgsm-devel,
libmp3lame-devel, libschroedinger1.0-devel, speex-devel, libtheora-devel,
libxvidcore-devel
@end example
The recommendation for libnut and x264 is to build them from source by
yourself, as they evolve too quickly for Cygwin Ports to be up to date.
Cygwin 1.7.x has IPv6 support. You can add IPv6 to Cygwin 1.5.x by means
of the @code{libgetaddrinfo-devel} package, available at Cygwin Ports.
@subsection Crosscompilation for Windows under Cygwin
With Cygwin you can create Windows binaries that do not need the cygwin1.dll.
Just install your Cygwin as explained before, plus these additional
"Devel" packages:
@example
gcc-mingw-core, mingw-runtime, mingw-zlib
@end example
and add some special flags to your configure invocation.
For a static build run
@example
./configure --target-os=mingw32 --enable-memalign-hack --enable-static --disable-shared --extra-cflags=-mno-cygwin --extra-libs=-mno-cygwin
@end example
and for a build with shared libraries
@example
./configure --target-os=mingw32 --enable-memalign-hack --enable-shared --disable-static --extra-cflags=-mno-cygwin --extra-libs=-mno-cygwin
@end example
@section BeOS
BeOS support is broken in mysterious ways.
@section OS/2
For information about compiling FFmpeg on OS/2 see
@url{http://www.edm2.com/index.php/FFmpeg}.
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@chapter Developers Guide
@section API
@itemize @bullet
@item libavcodec is the library containing the codecs (both encoding and
decoding). Look at @file{libavcodec/apiexample.c} to see how to use it.
@item libavformat is the library containing the file format handling (mux and
demux code for several formats). Look at @file{ffplay.c} to use it in a
player. See @file{output_example.c} to use it to generate audio or video
streams.
@end itemize
@section Integrating libavcodec or libavformat in your program
You can integrate all the source code of the libraries to link them
statically to avoid any version problem. All you need is to provide a
'config.mak' and a 'config.h' in the parent directory. See the defines
generated by ./configure to understand what is needed.
You can use libavcodec or libavformat in your commercial program, but
@emph{any patch you make must be published}. The best way to proceed is
to send your patches to the FFmpeg mailing list.
@node Coding Rules
@section Coding Rules
FFmpeg is programmed in the ISO C90 language with a few additional
features from ISO C99, namely:
@itemize @bullet
@item
the @samp{inline} keyword;
@item
@samp{//} comments;
@item
designated struct initializers (@samp{struct s x = @{ .i = 17 @};})
@item
compound literals (@samp{x = (struct s) @{ 17, 23 @};})
@end itemize
These features are supported by all compilers we care about, so we will not
accept patches to remove their use unless they absolutely do not impair
clarity and performance.
All code must compile with GCC 2.95 and GCC 3.3. Currently, FFmpeg also
compiles with several other compilers, such as the Compaq ccc compiler
or Sun Studio 9, and we would like to keep it that way unless it would
be exceedingly involved. To ensure compatibility, please do not use any
additional C99 features or GCC extensions. Especially watch out for:
@itemize @bullet
@item
mixing statements and declarations;
@item
@samp{long long} (use @samp{int64_t} instead);
@item
@samp{__attribute__} not protected by @samp{#ifdef __GNUC__} or similar;
@item
GCC statement expressions (@samp{(x = (@{ int y = 4; y; @})}).
@end itemize
Indent size is 4.
The presentation is the one specified by 'indent -i4 -kr -nut'.
The TAB character is forbidden outside of Makefiles as is any
form of trailing whitespace. Commits containing either will be
rejected by the Subversion repository.
The main priority in FFmpeg is simplicity and small code size in order to
minimize the bug count.
Comments: 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.
@example
/**
* @@file mpeg.c
* MPEG codec.
* @@author ...
*/
/**
* Summary sentence.
* more text ...
* ...
*/
typedef struct Foobar@{
int var1; /**< var1 description */
int var2; ///< 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)
...
@end example
fprintf and printf are forbidden in libavformat and libavcodec,
please use av_log() instead.
Casts should be used only when necessary. Unneeded parentheses
should also be avoided if they don't make the code easier to understand.
@section Development Policy
@enumerate
@item
Contributions should be licensed under the LGPL 2.1, including an
"or any later version" clause, or the MIT license. GPL 2 including
an "or any later version" clause is also acceptable, but LGPL is
preferred.
@item
You must not commit code which breaks FFmpeg! (Meaning unfinished but
enabled code which breaks compilation or compiles but does not work or
breaks the regression tests)
You can commit unfinished stuff (for testing etc), but it must be disabled
(#ifdef etc) by default so it does not interfere with other developers'
work.
@item
You do not have to over-test things. If it works for you, and you think it
should work for others, then commit. If your code has problems
(portability, triggers compiler bugs, unusual environment etc) they will be
reported and eventually fixed.
@item
Do not commit unrelated changes together, 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.
@item
Do not change behavior of the program (renaming options etc) without
first discussing it on the ffmpeg-devel mailing list. Do not remove
functionality from the code. Just improve!
Note: Redundant code can be removed.
@item
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.
@item
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.
NOTE: If you had to put if()@{ .. @} over a large (> 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
@item
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 "fixed!" or "Changed it." are unacceptable.
@item
If you apply a patch by someone else, include the name and email address in
the log message. Since the ffmpeg-cvslog mailing list is publicly
archived you should add some SPAM protection to the email address. Send an
answer to ffmpeg-devel (or wherever you got the patch from) saying that
you applied the patch.
@item
When applying patches that have been discussed (at length) on the mailing
list, reference the thread in the log message.
@item
Do NOT commit to code actively maintained by others without permission.
Send a patch to ffmpeg-devel instead. If no one answers within a reasonable
timeframe (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!
@item
Subscribe to the ffmpeg-cvslog mailing list. The diffs of all commits
are sent there and reviewed by all the other developers. Bugs and possible
improvements or general questions regarding commits are discussed there. We
expect you to react if problems with your code are uncovered.
@item
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.
@item
Try to keep important discussions and requests (also) on the public
developer mailing list, so that all developers can benefit from them.
@item
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.
@item
Remember to check if you need to bump versions for the specific libav
parts (libavutil, libavcodec, libavformat) you are changing. You need
Peter Ross
committed
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
Peter Ross
committed
(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).
@item
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.
@item
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.
@end enumerate
We think our rules are not too hard. If you have comments, contact us.
Note, these rules are mostly borrowed from the MPlayer project.
@section Submitting patches
First, (@pxref{Coding Rules}) above if you did not yet.