This directory contains files used in gecko builds from FFmpeg
(http://ffmpeg.org). The current files are from FFmpeg as of
revision n3.1.1-6-g86f9228
All source files match their path from the library's source archive.

Currently, we only use the vp8 and vp9 portion of the library, and only on x86
based platforms. If this changes, configuration files will most likely
need to be updated.

AVX2 must be disabled on Linux due to the use of yasm 1.1 on the build bots.
Once yasm is upgraded to 1.2 or later, AVX2 code could be re-enabled.
Add --disable-avx2 to configure on those platforms.

configuration files were generated as follow using the configure script:
./configure --disable-everything --disable-protocols --disable-demuxers --disable-muxers --disable-filters --disable-programs --disable-doc --disable-parsers --enable-parser=vp8 --enable-parser=vp9 --enable-decoder=vp8 --enable-decoder=vp9 --disable-static --enable-shared --disable-debug --disable-sdl --disable-libxcb --disable-securetransport --disable-iconv --disable-swresample --disable-swscale --disable-avdevice --disable-avfilter --disable-avformat --disable-d3d11va --disable-dxva2 --disable-vaapi --disable-vda --disable-vdpau --disable-videotoolbox --enable-asm --enable-yasm

config*:
replace: /HAVE_(MALLOC_H|ARC4RANDOM|LOCALTIME_R|MEMALIGN|POSIX_MEMALIGN)/d

config_darwin32.h:
add to configure command: --disable-asm --disable-yasm --cc='clang -m32'

config_unix32.h:
add to configure command: --disable-asm --disable-yasm --cc='clang -m32'
replace: s/HAVE_SYSCTL 1/HAVE_SYSCTL 0/ and s/HAVE_MEMALIGN 1/HAVE_MEMALIGN 0/ and s/HAVE_POSIX_MEMALIGN 1/HAVE_POSIX_MEMALIGN 0/


config_unix64.h/config_unix64.asm:
replace: s/HAVE_SYSCTL 1/HAVE_SYSCTL 0

config_win32/64.h/asm:
add to configure command: --toolchain=msvc

23 Sept 2016: libavcodec/pthread_frame.c has been patched so as to avoid
generating large numbers of warnings from TSan (Thread Sanitizer) when
decoding vp9 streams.  This will likely be fixed upstream sometime soon.
When resyncing with upstream, first un-apply the patch shown at
https://bugzilla.mozilla.org/show_bug.cgi?id=1274256#c60, then resync,
then assess whether the patch is still necessary.
