Xpra: Ticket #168: Build ffmpeg for win32

We have many problems with the pre-made builds of ffmpeg for win32, and they are much bigger than our needs. It therefore makes sense to build it ourselves, using only the components we need, and a stable release number instead of git revisions.

To build ffmpeg for win32, you need to set up mingw32.

Then, until the following ticket is fixed, you need to patch the "configure" script. http://ffmpeg.org/trac/ffmpeg/ticket/349?cversion=2&cnum_hist=3

# must change
#        SLIB_EXTRA_CMD='-lib.exe /machine:$(LIBTARGET)  def:$$(@:$(SLIBSUF)=.def) /out:$(SUBDIR)$(SLIBNAME:$(SLIBSUF)=.lib)'
#to         SLIB_EXTRA_CMD=-'i486-mingw32-dlltool -m $(LIBTARGET) -d $$(@:$(SLIBSUF)=.def) -l $(SUBDIR)$(SLIBNAME:$(SLIBSUF)=.lib) -D $(SLIBNAME_WITH_MAJOR)'

Change "i486-mingw32-dlltool" to the name for your mingw32 dlltool. (Sometimes i686-pc-mingw32-dlltool, ...).

Then:

./configure --disable-filters --disable-indevs --disable-encoders --disable-muxers --disable-avfilter --enable-runtime-cpudetect --disable-network --enable-gpl --enable-shared --enable-memalign-hack --disable-ffplay --disable-ffprobe --disable-ffserver --disable-ffmpeg --disable-dxva2 --cross-prefix=i486-mingw32- --enable-cross-compile --target-os=mingw32 --arch=x86  --prefix=/tmp/mingw32_ffmpeg_ah
make
make install

Notes:

• build hasn't been tested yet
• dxva2 is not built but it should - my mingw is missing dxva headers and I don't know where to find them