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# Platform Specific information

# 1. Unix-like

Some parts of Libav cannot be built with version 2.15 of the GNU assembler which is still provided by a few AMD64 distributions. To make sure your compiler really uses the required version of gas after a binutils upgrade, run:

    $(gcc -print-prog-name=as) --version

If not, then you should install a different compiler that has no hard-coded path to gas. In the worst case pass `--disable-asm` to configure.

## 1.1 Advanced linking configuration

If you compiled Libav libraries statically and you want to use them to build your own shared library, you may need to force PIC support (with `--enable-pic` during Libav configure) and add the following option to your project LDFLAGS:

    -Wl,-Bsymbolic

If your target platform requires position independent binaries, you should pass the correct linking flag (e.g. `-pie`) to `--extra-ldexeflags`.

## 1.2 BSD

BSD make will not build Libav, you need to install and use GNU Make (`gmake`).

## 1.3 (Open)Solaris

GNU Make is required to build Libav, so you have to invoke (`gmake`), standard Solaris Make will not work. When building with a non-c99 front-end (gcc, generic suncc) add either `--extra-libs=/usr/lib/values-xpg6.o` or `--extra-libs=/usr/lib/64/values-xpg6.o` to the configure options since the libc is not c99-compliant by default. The probes performed by configure may raise an exception leading to the death of configure itself due to a bug in the system shell. Simply invoke a different shell such as bash directly to work around this:

    bash ./configure

## 1.4 Darwin (OS X, iPhone)

The toolchain provided with Xcode is sufficient to build the basic unacelerated code.

OS X on PowerPC or ARM (iPhone) requires a preprocessor from git://git.libav.org/gas-preprocessor.git to build the optimized assembly functions. Put the Perl script somewhere in your PATH, Libav's configure will pick it up automatically.

OS X on AMD64 and x86 requires `yasm` to build most of the optimized assembly functions Homebrew, Gentoo Prefix or MacPorts can easily provide it.

# 2. DOS

Using a cross-compiler is preferred for various reasons. http://www.delorie.com/howto/djgpp/linux-x-djgpp.html

# 3. OS/2

For information about compiling Libav on OS/2 see http://www.edm2.com/index.php/FFmpeg.

# 4. Windows

## 4.1 Native Windows compilation using MinGW or MinGW-w64

Libav can be built to run natively on Windows using the MinGW or MinGW-w64 toolchains. Install the latest versions of MSYS and MinGW or MinGW-w64 from http://www.mingw.org/ or http://mingw-w64.sourceforge.net/. You can find detailed installation instructions in the download section and the FAQ.

Notes:

## 4.2 Microsoft Visual C++ or Intel C++ Compiler for Windows

Libav can be built with MSVC 2012 or earlier using a C99-to-C89 conversion utility and wrapper, or with MSVC 2013 and ICL natively.

You will need the following prerequisites:

To set up a proper environment in MSYS, you need to run `msys.bat` from the Visual Studio or Intel Compiler command prompt.

Place `yasm.exe` somewhere in your `PATH`. If using MSVC 2012 or earlier, place `c99wrap.exe` and `c99conv.exe` somewhere in your `PATH` as well.

Next, make sure any other headers and libs you want to use, such as zlib, are located in a spot that the compiler can see. Do so by modifying the `LIB` and `INCLUDE` environment variables to include the Windows-style paths to these directories. Alternatively, you can try and use the `--extra-cflags`/`--extra-ldflags` configure options. If using MSVC 2012 or earlier, place `inttypes.h` somewhere the compiler can see too.

Finally, run:

    For MSVC:
    ./configure --toolchain=msvc

    For ICL:
    ./configure --toolchain=icl

    make
    make install

If you wish to compile shared libraries, add `--enable-shared` to your configure options. Note that due to the way MSVC and ICL handle DLL imports and exports, you cannot compile static and shared libraries at the same time, and enabling shared libraries will automatically disable the static ones.

Notes:

### 4.2.1 Linking to Libav with Microsoft Visual C++

If you plan to link with MSVC-built static libraries, you will need to make sure you have `Runtime Library` set to `Multi-threaded (/MT)` in your project's settings.

You will need to define `inline` to something MSVC understands:

    #define inline __inline

Also note, that as stated in Microsoft Visual C++, you will need an MSVC-compatible inttypes.h.

If you plan on using import libraries created by dlltool, you must set `References` to `No (/OPT:NOREF)` under the linker optimization settings, otherwise the resulting binaries will fail during runtime. This is not required when using import libraries generated by `lib.exe`. This issue is reported upstream at http://sourceware.org/bugzilla/show_bug.cgi?id=12633.

To create import libraries that work with the `/OPT:REF` option (which is enabled by default in Release mode), follow these steps:

1. Open the Visual Studio Command Prompt.

   Alternatively, in a normal command line prompt, call ``vcvars32.bat'` which sets up the environment variables for the Visual C++ tools (the standard location for this file is something like ``C:\Program Files (x86_\Microsoft Visual Studio 10.0\VC\bin\vcvars32.bat'`).

2. Enter the ``bin'` directory where the created LIB and DLL files are stored.
3. Generate new import libraries with `lib.exe`:

       lib /machine:i386 /def:..\lib\foo-version.def  /out:foo.lib

   Replace `foo-version` and `foo` with the respective library names.

## 4.3 Cross compilation for Windows with Linux

You must use the MinGW cross compilation tools available at http://www.mingw.org/.

Then configure Libav with the following options:

    ./configure --target-os=mingw32 --cross-prefix=i386-mingw32msvc-

(you can change the cross-prefix according to the prefix chosen for the MinGW tools).

Then you can easily test Libav with Wine.

## 4.4 Compilation under Cygwin

Please use Cygwin 1.7.x as the obsolete 1.5.x Cygwin versions lack llrint() in its C library.

Install your Cygwin with all the "Base" packages, plus the following "Devel" ones:

    binutils, gcc4-core, make, git, mingw-runtime, texi2html

In order to run FATE you will also need the following "Utils" packages:

    bc, diffutils

If you want to build Libav with additional libraries, download Cygwin "Devel" packages for Ogg and Vorbis from any Cygwin packages repository:

    libogg-devel, libvorbis-devel

These library packages are only available from Cygwin Ports:

    yasm, libSDL-devel, libfaac-devel, libgsm-devel, libmp3lame-devel,
    libschroedinger1.0-devel, speex-devel, libtheora-devel, libxvidcore-devel

The recommendation for x264 is to build it from source, as it evolves too quickly for Cygwin Ports to be up to date.

## 4.5 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:

    gcc-mingw-core, mingw-runtime, mingw-zlib

and add some special flags to your configure invocation.

For a static build run

    ./configure --target-os=mingw32 --extra-cflags=-mno-cygwin --extra-libs=-mno-cygwin

and for a build with shared libraries

    ./configure --target-os=mingw32 --enable-shared --disable-static --extra-cflags=-mno-cygwin --extra-libs=-mno-cygwin

# 5. Plan 9

The native Plan 9 compiler does not implement all the C99 features needed by Libav so the gcc port must be used. Furthermore, a few items missing from the C library and shell environment need to be fixed.

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