Those are preliminary information on how to enable HD audio passthrough over HDMI (currenly E-AC3 and TrueHD).
You'll need a recent linux kernel (>= 2.6.36) that contains the required ALSA drivers. Alternatively get the latest ALSA driver from the git repository
git clone git://git.alsa-project.org/alsa-driver.git alsa-driver git clone git://git.alsa-project.org/alsa-kmirror.git alsa-kmirror cd alsa-driver ./gitcompile sudo make install
Alsa library 1.0.23 is the required minimum. However if you had to mess with the device name to get basic audio working, it is strongly recommended you get a new version as otherwise you will likely have to mess with alsa configuration file.
git clone git://git.alsa-project.org/alsa-lib.git alsa-lib cd alsa-lib ./git-compile sudo make install