I have a Sony STR DE885 receiver. I have been running it in Matrix mode (Surround Back Decoding). I started trying to confirm that in this mode it would use the 6.1 Surround information encoded in Surround EX films when present, and build it from the 5.1 when it was not present.
After contacting Sony twice, I still cannot confirm that is what the Matrix setting does, so I decided to do some testing. I switched the receiver to Auto, which is only supposed to provide sound to the surround back speaker if the disc is Surround EX, and then I stuck in Lord of the Rings, which is Surround EX. This combo gave me [B]no rear surround[/B].
Now I am totally confused. I have my DVD player (Toshiba SD-3800) hooked to my Sony receiver via Coax digitial in. I have the DVD audio set to digital bitstream (as opposed to PCM). The receiver clearly recognizes the difference between 2 channel stereo inputs and 5.1 inputs, but doesn't seem to be recognizing 6.1 discs.