general.texi

ffmpeg的完整源代码和作者自己写的文档。不但有在Linux的工程哦

@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

BeOS support is broken in mysterious ways.

@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