May as well post this now, the information I have collected may be useful.
Trying to get True-HD and DTS-MA working, as that is the main reason for building this htpc.
Progress was reasonably good until trying to fix the final issue - HD sound.
I have done numerous builds and configurations with ubuntu 11.10, and now 12.04, and XBMC from 11.0 RC1 -> RC2 -> release, pulseaudio-patch, audioengine.
Several attempts to install drivers and alsa versions.
This configuration is the closest I have come to a working system:
XBMC 12.0-ALPHA1 Git:20120416-afbac7c, Platform: Linux (Ubuntu precise (development branch), 3.2.0-23-generic-pae i686). Built on Apr 16 2012.
All drivers and alsa are from the ubuntu 12.04.
Still, there is only distorted, noisy sound when playing anything HD (Dolby True HD, DTS MA).
2-ch PCM, DTS, DD, DTS.HD (5.1/24-96) works, on HDMI.
Asus P8H67I-Deluxe with Intel i3 2120 cpu, 4Gb RAM.
(Intel Cougarpoint HD audio).
HDMI to AV receiver.
Tested on Win7-install where everything works fine, including TrueHD, DTS-MA (Verified by inspecting audio format detected by receiver - channels, codec, sample rates).
Intel CougarPoint HDMI
xbmc log; start xbmc - open and play truehd clip - exit:
xbmc log; start xbmc - open and play dts-ma clip - exit: