OK here is my problem, but I think I had figured it out. Just to to be safe, or in case I am missing something, here goes.
I have a 6 year old ONKYO TX-SR605 receiver. It has two HDMI inputs and one output. I have a Sony XBR4 TV. Monoprices' HDMI cables.
I have the TV hdmi 1 to the onkyo out.
I have my PS3 in hdmi 1 on the Onkyo.
I have my xbox360 in hdmi 2 on the Onkyo.
I just got cable installed in this room. So I am using the TV hdmi 3 to the Comcast hdmi.
Problem is since the hdmi 3 has no place to go on the reciever I get picture, but no sound. The only way I can get around this is put an optical cable from the Comcast box to a jack on the Onkyo, and the go to the recievers settings to turn the optical sound on.
So, is this the only way? Or, is there something I am not thinking of? Another way would be to A) buy a newer reciever. B) buy a hdmi ext. C) just swap the hdmi from ps or xbox.