ffmpeg-doc.texi

@item H.261                  @tab  X  @tab  X
@item H.263(+)               @tab  X  @tab  X @tab also known as RealVideo 1.0
@item H.264                  @tab     @tab  X
@item RealVideo 1.0          @tab  X  @tab  X
@item RealVideo 2.0          @tab  X  @tab  X
@item MJPEG                  @tab  X  @tab  X
@item lossless MJPEG         @tab  X  @tab  X
@item JPEG-LS                @tab  X  @tab  X @tab fourcc: MJLS, lossless and near-lossless is supported
@item Apple MJPEG-B          @tab     @tab  X
@item Sunplus MJPEG          @tab     @tab  X @tab fourcc: SP5X
@item DV                     @tab  X  @tab  X
@item HuffYUV                @tab  X  @tab  X
@item FFmpeg Video 1         @tab  X  @tab  X @tab experimental lossless codec (fourcc: FFV1)
@item FFmpeg Snow            @tab  X  @tab  X @tab experimental wavelet codec (fourcc: SNOW)
@item Asus v1                @tab  X  @tab  X @tab fourcc: ASV1
@item Asus v2                @tab  X  @tab  X @tab fourcc: ASV2
@item Creative YUV           @tab     @tab  X @tab fourcc: CYUV
@item Sorenson Video 1       @tab  X  @tab  X @tab fourcc: SVQ1
@item Sorenson Video 3       @tab     @tab  X @tab fourcc: SVQ3
@item On2 VP3                @tab     @tab  X @tab still experimental
@item On2 VP5                @tab     @tab  X @tab fourcc: VP50
@item On2 VP6                @tab     @tab  X @tab fourcc: VP60,VP61,VP62
@item Theora                 @tab  X  @tab  X @tab still experimental
@item Intel Indeo 3          @tab     @tab  X
@item FLV                    @tab  X  @tab  X @tab Sorenson H.263 used in Flash
@item Flash Screen Video     @tab  X  @tab  X @tab fourcc: FSV1
@item ATI VCR1               @tab     @tab  X @tab fourcc: VCR1
@item ATI VCR2               @tab     @tab  X @tab fourcc: VCR2
@item Cirrus Logic AccuPak   @tab     @tab  X @tab fourcc: CLJR
@item 4X Video               @tab     @tab  X @tab Used in certain computer games.
@item Sony Playstation MDEC  @tab     @tab  X
@item Id RoQ                 @tab  X  @tab  X @tab Used in Quake III, Jedi Knight 2, other computer games.
@item Xan/WC3                @tab     @tab  X @tab Used in Wing Commander III .MVE files.
@item Interplay Video        @tab     @tab  X @tab Used in Interplay .MVE files.
@item Apple Animation        @tab  X  @tab  X @tab fourcc: 'rle '
@item Apple Graphics         @tab     @tab  X @tab fourcc: 'smc '
@item Apple Video            @tab     @tab  X @tab fourcc: rpza
@item Apple QuickDraw        @tab     @tab  X @tab fourcc: qdrw
@item Cinepak                @tab     @tab  X
@item Microsoft RLE          @tab     @tab  X
@item Microsoft Video-1      @tab     @tab  X
@item Westwood VQA           @tab     @tab  X
@item Id Cinematic Video     @tab     @tab  X @tab Used in Quake II.
@item Planar RGB             @tab     @tab  X @tab fourcc: 8BPS
@item FLIC video             @tab     @tab  X
@item Duck TrueMotion v1     @tab     @tab  X @tab fourcc: DUCK
@item Duck TrueMotion v2     @tab     @tab  X @tab fourcc: TM20
@item VMD Video              @tab     @tab  X @tab Used in Sierra VMD files.
@item MSZH                   @tab     @tab  X @tab Part of LCL
@item ZLIB                   @tab  X  @tab  X @tab Part of LCL, encoder experimental
@item TechSmith Camtasia     @tab     @tab  X @tab fourcc: TSCC
@item IBM Ultimotion         @tab     @tab  X @tab fourcc: ULTI
@item Miro VideoXL           @tab     @tab  X @tab fourcc: VIXL
@item QPEG                   @tab     @tab  X @tab fourccs: QPEG, Q1.0, Q1.1
@item LOCO                   @tab     @tab  X @tab
@item Winnov WNV1            @tab     @tab  X @tab
@item Autodesk Animator Studio Codec  @tab     @tab  X @tab fourcc: AASC
@item Fraps FPS1             @tab     @tab  X @tab
@item CamStudio              @tab     @tab  X @tab fourcc: CSCD
@item American Laser Games Video  @tab    @tab X @tab Used in games like Mad Dog McCree
@item ZMBV                   @tab   X @tab  X @tab Encoder works only on PAL8
@item AVS Video              @tab     @tab  X @tab Video encoding used by the Creature Shock game.
@item Smacker Video          @tab     @tab  X @tab Video encoding used in Smacker.
@item RTjpeg                 @tab     @tab  X @tab Video encoding used in NuppelVideo files.
@item KMVC                   @tab     @tab  X @tab Codec used in Worms games.
@item VMware Video           @tab     @tab  X @tab Codec used in videos captured by VMware.
@item Cin Video              @tab     @tab  X @tab Codec used in Delphine Software games.
@item Tiertex Seq Video      @tab     @tab  X @tab Codec used in DOS CDROM FlashBack game.
@item DXA Video              @tab     @tab  X @tab Codec originally used in Feeble Files game.
@item AVID DNxHD             @tab     @tab  X @tab aka SMPTE VC3
@item C93 Video              @tab     @tab  X @tab Codec used in Cyberia game.
@item THP                    @tab     @tab  X @tab Used on the Nintendo GameCube.
@item Bethsoft VID           @tab     @tab  X @tab Used in some games from Bethesda Softworks.
@item Renderware TXD         @tab     @tab  X @tab Texture dictionaries used by the Renderware Engine.
@end multitable

@code{X} means that encoding (resp. decoding) is supported.

@section Audio Codecs

@multitable @columnfractions .4 .1 .1 .1 .7
@item Supported Codec @tab Encoding @tab Decoding @tab Comments
@item MPEG audio layer 2     @tab  IX  @tab  IX
@item MPEG audio layer 1/3   @tab IX   @tab  IX
@tab MP3 encoding is supported through the external library LAME.
@item AC3                    @tab  IX  @tab  IX
@tab liba52 is used internally for decoding.
@item Vorbis                 @tab  X   @tab  X
@item WMA V1/V2              @tab X    @tab X
@item AAC                    @tab X    @tab X
@tab Supported through the external library libfaac/libfaad.
@item Microsoft ADPCM        @tab X    @tab X
@item MS IMA ADPCM           @tab X    @tab X
@item QT IMA ADPCM           @tab      @tab X
@item 4X IMA ADPCM           @tab      @tab X
@item G.726  ADPCM           @tab X    @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 Westwood Studios IMA ADPCM @tab      @tab X
@tab Used in Westwood Studios games like Command and Conquer.
@item SMJPEG IMA ADPCM       @tab      @tab X
@tab Used in certain Loki game ports.
@item CD-ROM XA ADPCM        @tab      @tab X
@item CRI ADX ADPCM          @tab X    @tab X
@tab Used in Sega Dreamcast games.
@item Electronic Arts ADPCM  @tab      @tab X
@tab Used in various EA titles.
@item Creative ADPCM         @tab      @tab X
@tab 16 -> 4, 8 -> 4, 8 -> 3, 8 -> 2
@item THP ADPCM              @tab      @tab X
@tab Used on the Nintendo GameCube.
@item RA144                  @tab      @tab X
@tab Real 14400 bit/s codec
@item RA288                  @tab      @tab X
@tab Real 28800 bit/s codec
@item RADnet                 @tab X    @tab IX
@tab Real low bitrate AC3 codec, liba52 is used for decoding.
@item AMR-NB                 @tab X    @tab X
@tab Supported through an external library.
@item AMR-WB                 @tab X    @tab X
@tab Supported through an external library.
@item DV audio               @tab      @tab X
@item Id RoQ DPCM            @tab X    @tab X
@tab Used in Quake III, Jedi Knight 2, other computer games.
@item Interplay MVE DPCM     @tab      @tab X
@tab Used in various Interplay computer games.
@item Xan DPCM               @tab      @tab X
@tab Used in Origin's Wing Commander IV AVI files.
@item Sierra Online DPCM     @tab      @tab X
@tab Used in Sierra Online game audio files.
@item Apple MACE 3           @tab      @tab X
@item Apple MACE 6           @tab      @tab X
@item FLAC lossless audio    @tab X    @tab X
@item Shorten lossless audio @tab      @tab X
@item Apple lossless audio   @tab      @tab X
@tab QuickTime fourcc 'alac'
@item FFmpeg Sonic           @tab X    @tab X
@tab experimental lossy/lossless codec
@item Qdesign QDM2           @tab      @tab X
@tab there are still some distortions
@item Real COOK              @tab      @tab X
@tab All versions except 5.1 are supported
@item DSP Group TrueSpeech   @tab      @tab X
@item True Audio (TTA)       @tab      @tab X
@item Smacker Audio          @tab      @tab X
@item WavPack Audio          @tab      @tab X
@item Cin Audio              @tab      @tab X
@tab Codec used in Delphine Software games.
@item Intel Music Coder      @tab      @tab X
@item Musepack               @tab      @tab X
@tab Only SV7 is supported
@item DT$ Coherent Audio     @tab      @tab X
@item ATRAC 3                @tab      @tab X
@end multitable

@code{X} means that encoding (resp. decoding) is supported.

@code{I} means that an integer-only version is available, too (ensures high
performance on systems without hardware floating point support).

@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 using FFmpeg under Windows, check out
the FFmpeg Windows Help Forum at
@url{http://arrozcru.no-ip.org/ffmpeg/}.

@subsection Native Windows compilation

@itemize
@item Install the current versions of MSYS and MinGW from
@url{http://www.mingw.org/}. You can find detailed installation
instructions in the download section and the FAQ.

NOTE: Use at least bash 3.1. Older versions are known to be failing on the
configure script.

@item If you want to test the FFplay, also download
the MinGW development library of SDL 1.2.x
(@file{SDL-devel-1.2.x-mingw32.tar.gz}) from
@url{http://www.libsdl.org}. Unpack it in a temporary directory, and
unpack the archive @file{i386-mingw32msvc.tar.gz} in the MinGW tool
directory. Edit the @file{sdl-config} script so that it gives the
correct SDL directory when invoked.

@item If you want to use 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 Extract the current version of FFmpeg.

@item Start the MSYS shell (file @file{msys.bat}).

@item Change to the FFmpeg directory and follow
 the instructions of how to compile FFmpeg (file
@file{INSTALL}). Usually, launching @file{./configure} and @file{make}
suffices. If you have problems using SDL, verify that
@file{sdl-config} can be launched from the MSYS command line.

@item You can install FFmpeg in @file{Program Files/FFmpeg} by typing
@file{make install}. Do not forget to copy @file{SDL.dll} to the place
you launch @file{ffplay} from.

@end itemize

Notes:
@itemize

@item The target @file{make wininstaller} can be used to create a
Nullsoft based Windows installer for FFmpeg and FFplay. @file{SDL.dll}
must be copied to the FFmpeg directory in order to build the
installer.

@item By using @code{./configure --enable-shared} when configuring FFmpeg,
you can build @file{avcodec.dll} and @file{avformat.dll}. With
@code{make install} you install the FFmpeg DLLs and the associated
headers in @file{Program Files/FFmpeg}.

@item Visual C++ compatibility: If you used @code{./configure --enable-shared}
when configuring FFmpeg, FFmpeg tries to use the Microsoft Visual
C++ @code{lib} tool to build @code{avcodec.lib} and
@code{avformat.lib}. With these libraries you can link your Visual C++
code directly with the FFmpeg DLLs (see below).

@end itemize

@subsection Visual C++ compatibility

FFmpeg will not compile under Visual C++ -- and it has too many
dependencies on the GCC compiler to make a port viable. However,
if you want to use the FFmpeg libraries in your own applications,
you can still compile those applications using Visual C++. An
important restriction to this is that you have to use the
dynamically linked versions of the FFmpeg libraries (i.e. the
DLLs), and you have to make sure that Visual-C++-compatible
import libraries are created during the FFmpeg build process.

This description of how to use the FFmpeg libraries with Visual C++ is
based on Visual C++ 2005 Express Edition Beta 2. If you have a different
version, you might have to modify the procedures slightly.

Here are the step-by-step instructions for building the FFmpeg libraries
so they can be used with Visual C++:

@enumerate

@item Install Visual C++ (if you have not done so already).

@item Install MinGW and MSYS as described above.

@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}:

@code{call "C:\Program Files\Microsoft Visual Studio 8\VC\bin\vcvars32.bat"}

@item Start the MSYS shell (file @file{msys.bat}) and type @code{link.exe}.
If you get a help message with the command line options of @code{link.exe},
this means your environment variables are set up correctly, the
Microsoft linker is on the path and will be used by FFmpeg to
create Visual-C++-compatible import libraries.

@item Extract the current version of FFmpeg and change to the FFmpeg directory.

@item Type the command
@code{./configure --enable-shared --disable-static --enable-memalign-hack}
to configure and, if that did not produce any errors,
type @code{make} to build FFmpeg.

@item The subdirectories @file{libavformat}, @file{libavcodec}, and
@file{libavutil} should now contain the files @file{avformat.dll},
@file{avformat.lib}, @file{avcodec.dll}, @file{avcodec.lib},
@file{avutil.dll}, and @file{avutil.lib}, respectively. Copy the three
DLLs to your System32 directory (typically @file{C:\Windows\System32}).

@end enumerate

And here is how to use these libraries with Visual C++:

@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 Visual C++ has already created for you. (Note that your source
filehas to have a @code{.cpp} extension; otherwise, Visual C++ will not
compile the FFmpeg headers correctly because in C mode, it does not
recognize the @code{inline} keyword.)  For example, you can copy
@file{output_example.c} from the FFmpeg distribution (but you will
have to make minor modifications so the code will compile under
C++, see below).

@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 complete paths to the
@file{libavformat}, @file{libavcodec}, and @file{libavutil}
subdirectories of your FFmpeg directory. Note that the directories have
to be separated using semicolons. Now select "Linker / General" from the
tree view and edit the "Additional Library Directories" setting to
contain the same three directories.

@item Still in the "Project / Properties" dialog box, select "Linker / Input"
from the tree view, then add the files @file{avformat.lib},
@file{avcodec.lib}, and @file{avutil.lib} to the end of the "Additional
Dependencies". Note that the names of the libraries have to be separated
using spaces.

@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".

@item Click "OK" to close the "Project / Properties" dialog box and build
the application. Hopefully, it should compile and run cleanly. If you
used @file{output_example.c} as your sample application, you will get a
few compiler errors, but they are easy to fix. The first type of error
occurs because Visual C++ does not allow an @code{int} to be converted to
an @code{enum} without a cast. To solve the problem, insert the required
casts (this error occurs once for a @code{CodecID} and once for a
@code{CodecType}).  The second type of error occurs because C++ requires
the return value of @code{malloc} to be cast to the exact type of the
pointer it is being assigned to. Visual C++ will complain that, for
example, @code{(void *)} is being assigned to @code{(uint8_t *)} without
an explicit cast. So insert an explicit cast in these places to silence
the compiler. The third type of error occurs because the @code{snprintf}
library function is called @code{_snprintf} under Visual C++.  So just
add an underscore to fix the problem. With these changes,
@file{output_example.c} should compile under Visual C++, and the
resulting executable should produce valid video files.

@end enumerate

@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

Cygwin works very much like Unix.

Just install your Cygwin with all the "Base" packages, plus the
following "Devel" ones:
@example
binutils, gcc-core, make, subversion
@end example

Do not install binutils-20060709-1 (they are buggy on shared builds);
use binutils-20050610-1 instead.

Then run

@example
./configure --enable-static --disable-shared
@end example

to make a static build or

@example
./configure --enable-shared --disable-static
@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
and/or SDL, xvid, faac, faad2 packages from Cygwin Ports,
(@url{http://cygwinports.dotsrc.org/}).

@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

The configure script should guess the configuration itself.
Networking support is currently not finished.
errno issues fixed by Andrew Bachmann.

Old stuff:

François Revol - revol at free dot fr - April 2002

The configure script should guess the configuration itself,
however I still did not test building on the net_server version of BeOS.

FFserver is broken (needs poll() implementation).

There are still issues with errno codes, which are negative in BeOS, and
that FFmpeg negates when returning. This ends up turning errors into
valid results, then crashes.
(To be fixed)

@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
    to change the version integer and the version string.
    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).
    Incrementing the third component means a noteworthy binary compatible
    change (e.g. encoder bug fix that matters for the decoder).
@item
    If you add a new codec, remember to update the changelog, add it to
    the supported codecs table in the documentation and bump the second
    component of the @file{libavcodec} version number appropriately. If
    it has a fourcc, add it to @file{libavformat/avienc.c}, even if it
    is only a decoder.
@item
    Do not change code to hide warnings without ensuring that the underlying
    logic is correct and thus the warning was inappropriate.
@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.

When you submit your patch, try to send a unified diff (diff '-up'
option). I cannot read other diffs :-)

Also please do not submit patches which contain several unrelated changes.
Split them into individual self-contained patches; this makes reviewing
them much easier.

Run the regression tests before submitting a patch so that you can
verify that there are no big problems.

Patches should be posted as base64 encoded attachments (or any other
encoding which ensures that the patch will not be trashed during
transmission) to the ffmpeg-devel mailing list, see
@url{http://lists.mplayerhq.hu/mailman/listinfo/ffmpeg-devel}

It also helps quite a bit if you tell us what the patch does (for example
'replaces lrint by lrintf'), and why (for example '*BSD isn't C99 compliant
and has no lrint()')

Also please if you send several patches, send each patch as a separate mail,
do not attach several unrelated patches to the same mail.

@section patch submission checklist

@enumerate
@item
    Do the regression tests pass with the patch applied?
@item
    Is the patch a unified diff?
@item
    Is the patch against latest FFmpeg SVN?
@item
    Are you subscribed to ffmpeg-dev?
    (the list is subscribers only due to spam)
@item
    Have you checked that the changes are minimal, so that the same cannot be
    achieved with a smaller patch and/or simpler final code?
@item
    If the change is to speed critical code, did you benchmark it?
@item
    If you did any benchmarks, did you provide them in the mail?
@item
    Have you checked that the patch does not introduce buffer overflows or
    other security issues?
@item
    Is the patch created from the root of the source tree, so it can be
    applied with @code{patch -p0}?
@item
    Does the patch not mix functional and cosmetic changes?
@item
    Did you add tabs or trailing whitespace to the code? Both are forbidden.
@item
    Is the patch attached to the email you send?
@item
    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.
@item
    If the patch fixes a bug, did you provide a verbose analysis of the bug?
@item
    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 >100k to mails but rather provide a
    URL, you can upload to ftp://upload.mplayerhq.hu
@item
    Did you provide a verbose summary about what the patch does change?
@item
    Did you provide a verbose explanation why it changes things like it does?
@item
    Did you provide a verbose summary of the user visible advantages and
    disadvantages if the patch is applied?
@item
    Did you provide an example so we can verify the new feature added by the
    patch easily?
@item
    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.
@item
    You should maintain alphabetical order in alphabetically ordered lists as
    long as doing so does not break API/ABI compatibility.
@item
    Lines with similar content should be aligned vertically when doing so
    improves readability.
@item
    Did you provide a suggestion for a clear commit log message?
@end enumerate

@section Patch review process

All patches posted to ffmpeg-devel will be reviewed, unless they contain a
clear note that the patch is not for SVN.
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.

We will review all submitted patches, but sometimes we are quite busy so
especially for large patches this can take several weeks.

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.

@section Regression tests

Before submitting a patch (or committing to the repository), you should at least
test that you did not break anything.

The regression tests build a synthetic video stream and a synthetic
audio stream. These are then encoded and decoded with all codecs or
formats. The CRC (or MD5) of each generated file is recorded in a
result file. A 'diff' is launched to compare the reference results and
the result file.

The regression tests then go on to test the FFserver code with a
limited set of streams. It is important that this step runs correctly
as well.

Run 'make test' to test all the codecs and formats.

Run 'make fulltest' to test all the codecs, formats and FFserver.

[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].

@bye