Well, DTS is already something like 6 times the data rate of DD, so I'm not sure if a 16% reduction in data rate per channel is going to cause any perceptable effects. Unless, that is, the DTS encoding algorithm is drastically less efficient than DD's.

I don't remember the exact data rates, and I know they can vary, but I think that DD is usually something like 384kbps whereas DTS is in the range of 2.0Mbps.

I hear what you're saying about the compression artifacts, and that's something that I'd not considered. But I'm not sure that it would be all that apparent. Both the rear channel and the surround channels are, in fact, audio, and summing two audio tracks results in an audio track. One would hope that DTS's encoding algorithm would be able to encode any reasonable audio track without intorucing perceptable artificats, especially at the data rates that it consumes.

The compression argument aside, though, you still have three true discrete rear channels whether they are represented as LS, CS, RS, or LS+CS, CS, CS+RS. A matrix encoder normally doesn't know what RS is, which is why it has to make psychoacoustic "guesses." This is what sets matrix algorithms apart from discrete audio. Once CS is a known quantity, however, then LS ans RS can be easily derived.

It is still directly behind your head, though.

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Matthew J. Hill
matt@idsi.net