Xbox outputting pcm 48 only when tv is on...

So here is my set up I have my Xbox 360 with hdmi out to my Reciever and an hdmi out from my reciever to my tv.

When I turn on my xbox and reciver my receiver says (5.1) but as soon as I turn on my TV it changed to cpcm 48...Any advice?

help?

Don't know. Should only happen with the dashboard and not in-game/in-movie.

That's the thing when i'm in game I can hear things behind me and like it is 5.1 but the reciever says cpcm 48.

no one has a clue?

I'm guessing cPCM would mean compressed, which means either Dolby Digital or DTS. The 360 can't output loseless surround sound like the PS3 can, so this is correct.

Okay thanks! It's just weird when I had it outputting through optical it showed 5.1 :/