I haven't watched a whole lot of dvd's on my xbox since I modded it, so I just noticed this last night while watching Austin Powers in Goldmember (using DVDx 2, using optical cable obviously (just to avoid dumb questions)). I chose the DTS output, and got nothing. When I chose Dolby Digital, I got a Pro Logic output (I know this because my rcvr has different displays for all the different audio formats). I brought up the DVDX setup menu, and tried to change the audio outputs, and each time I opened that menu, the settings had reset to the first value.
I'm pretty sure that my xbox did Dolby 5.1 and DTS before I modded it, so I left the movie in the player, and from the EVOX menu, I booted to the Xbox Dashboard (with the DVD Playback kit plugged in). This allowed me to use the original XBOX DVD player. When looking at the audio setup while the movie was playing, it menu said it was outputting Dolby Digital 5.1, but the rcvr still saw ProLogic and DTS didn't work at all. I tested my rcvr using my ps2, just to make sure it was reading the proper audio formats, and it was fine for both DD and DTS.
This isn't a huge deal, I can just use my PS2 or my other DVD player to watch movies, but it's still frustrating...Anyone got any ideas?