Gotcha. Upon more reasearch (your posts and some more online articles at smr review and other places), i've concluded that a matrix-type decoder (such as a DPL box) will approximate the DD EX monaural channel just fine =)

dts ES discrete, on the other hand, cannot be approximated, interpolated, extrapolated, or calculated from the SL and SR channels. It is its own fully discrete channel... you could have mickey mouse singing "it's a small world" in the ES (SB) channel while Sigourney Weaver trounces aliens in the other 5.1 channels, if the sound engineers decided to encode the disc that way ;)

I also discovered that there really is a difference (according to Dolby and SMR) in the way the formats are labeled.

Dolby Digital Surround EX is our wonderful DPLish matrixed sound. SL+SR = SB Sum (woot!) (different from L-R+delay, but who really cares?)

Digital Theater Sound (dts) ES is 6.1 fully discreet tracks of gloriously independent audio. completely independent of Dolby Labs in every way.

"matrixed" dts ES should really be called:
Digital Theater Sound Dolby Digital Surround EX, because the matrix technology that is used is identical to DD EX, its just licensed from Dolby.

Suddenly, it all makes sense... sort of ;)

Thanks for the brainstorming,

-jer

BUT, as I understand it, DTS ES Discrete is also DTS ES Matrix compatible - so you can still use a DPL processor to decode the rear channels (if you have the right pre-outs/processor setup of course).