Good description of audio formats on hi-def disks/players at HIgh Def Digest.  It shows the complicated mess but gives the details to help make decisions (including when HDMI 1.3 is required). 

http://www.highdefdigest.com/news/show/Joshua_Zyber/High-Def_FAQ:_Blu-ray_and_HD_DVD_Audio_Explained/1064

Nice straight-forward link Ken...

Thanks!