I think I'm having the same problem, but I am not sure. I have HDMI going from the PS3 to the receiver and whether I play BR, DVD, or games my receiver is showing PCM. I hook the same hdmi cable to the xbox360 and the receiver says dolby digital.
You guys are saying this is not a problem and I am getting the correct sound, only the PS3 is doing the decoding (that xbox360 doesn't) therefore the receiver is just showing pcm?
I went through the setup and all the sound formats are checked and everything.