What happens when you play a dvd, (or a HDTV television signal), encoded with DD 5.1, over a 6.1 or 7.1 system? Do you get anything from the rear(s)? I assume :b that one of two things happen: a receiver extrapolates the 5.1 information and spreads it to all speakers in the system, be it 6.1 or 7.1, or, only signals that contain information for the rear,(or rears), will output to the speakers. I know that in Dolby Pro II, (or any of the other proprietary systems), sound is spread to all speakers no matter what the original signal may be. I guess I'm asking what happens in Dolby Digital?