Comment 18 for bug 595661

The included Intel driver in Precise still misses support for H.264 and the G45 chips. To solve this issue quickly, one can use these commands:
git clone git://anongit.freedesktop.org/vaapi/intel-driver intel-driver
cd intel-driver/
apt-cache show libva1|grep Version
git checkout 1.0.15 (replace 1.0.15 with the version from above when it differs)
git pull origin g45-h264
./autogen.sh
make
sudo make install

I haven't tested with playing videos yet, but this makes vainfo show three extra H264 profiles.