Intel had a problem with bitstreaming the HD Audio formats although they could be decoded to Multichannel PCM, description of problem & patches at https://bugs.freedesktop.org/show_bug.cgi?id=49055
Discussion here at http://forum.xbmc.org/showthread.php?tid=128298&page=42
Posts #418 to #446
As I don't know Linux well & follow the Linux developments closely I don't know if the patches made it into Linux kernal 3.7 and what kernel XBMCbuntu is using.
If users are going to have to compile the patch to get HD Audio working on Intel then it would be good if someone with some know how documents the problem & solution, it's not something I'd feel comfortable doing with my limited knowledge.
ATI issues on Linux described @ http://forum.xbmc.org/showthread.php?tid...pid1074967