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
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