Enabling hardware decode codepaths on linux #

Hardware acceleration of video decode on Linux is unsupported in Chrome for user-facing builds. During development (targeting other platforms) it can be useful to be able to trigger the code-paths used on HW-accelerated platforms (such as CrOS and win7) in a linux-based development environment. Here's one way to do so, with details based on a gprecise setup.

Install pre-requisites: On Ubuntu Precise, at least, this includes:
```
sudo apt-get install libtool libvdpau1 libvdpau-dev
```

Install and configure libva

DEST=${HOME}/apps/libva
cd /tmp
git clone git://anongit.freedesktop.org/libva
cd libva
git reset --hard libva-1.2.1
./autogen.sh && ./configure --prefix=${DEST}
make -j32 && make install

Install and configure the VDPAU VAAPI driver

DEST=${HOME}/apps/libva
cd /tmp
git clone git://anongit.freedesktop.org/vaapi/vdpau-driver
cd vdpau-driver
export PKG_CONFIG_PATH=${DEST}/lib/pkgconfig/:$PKG_CONFIG_PATH
export LIBVA_DRIVERS_PATH=${DEST}/lib/dri
export LIBVA_X11_DEPS_CFLAGS=-I${DEST}/include
export LIBVA_X11_DEPS_LIBS=-L${DEST}/lib
export LIBVA_DEPS_CFLAGS=-I${DEST}/include
export LIBVA_DEPS_LIBS=-L${DEST}/lib
make distclean
unset CC CXX
./autogen.sh && ./configure --prefix=${DEST} --enable-debug
find . -name Makefile |xargs sed -i 'sI/usr/lib/xorg/modules/driversI${DEST}/lib/driIg'
sed -i -e 's/_(\(VAEncH264VUIBufferType\|VAEncH264SEIBufferType\));//' src/vdpau_dump.c
make -j32 && rm -f ${DEST}/lib/dri/{nvidia_drv_video.so,s3g_drv_video.so} && make install

Add to $GYP_DEFINES:
- chromeos=1 to link in VaapiVideoDecodeAccelerator
- proprietary_codecs=1 ffmpeg_branding=Chrome to allow Chrome to play h.264 content, which is the only codec VAVDA knows about today.
Re-run gyp (./build/gyp_chromium or gclient runhooks)
Rebuild chrome
Run chrome with LD_LIBRARY_PATH=${HOME}/apps/libva/lib in the environment, and with the --no-sandbox command line flag.
If things don't work, a Debug build (to include D*LOG's) with --vmodule=*content/common/gpu/media/*=10,gpu_video*=1 might be enlightening.

note NOTE THIS IS AN UNSUPPORTED CONFIGURATION AND LIKELY TO BE BROKEN AT ANY POINT IN TIME

This page is purely here to help developers targeting supported HW <video> decode platforms be more effective. Do not expect help if this setup fails to work.