I am going to answer my own question. I checked the Chicago-land OTA HD thread at AVS Forum, and all my locals are broadcasting their HD with DD 5.1......soooooo, back to the drawing board.

I suspect the place to focus your attention is the software associated with your sound card - particularly your HD tuner card. Clearly the sound card is allowing DD and DTS bitstreams to pass under certain circumstances, because you are seeing them with DVD's. It's on the games and tuner that you're losing out.

The game makes a certain amount of sense: the audio is generated "on the fly" and as such can't be encoded as Dolby Digital in advance. That means that either the game or the sound card needs to take multichannel PCM and encode it on the fly into a Dolby Digital (or DTS) bitstream. The new HD-DVD players are doing this by decoding Dolby Digital Plus and TrueHD, then re-encoding as high-bitrate DTS, but I suspect it takes quite a bit of processing power. I wouldn't be surprised if the game only "supports" it if the sound card can provide the encoding.

HD broadcasts should not be in PCM - they should at least be Dolby Digital 2.0 (meaning "Dolby Digital" and no "PCM" on the 990's front panel), with some prime time material in 5.1. I wonder if the HD tuner card is somehow decoding to PCM before handing off the audio signal?

Gonk--the mystery continues. If I use my HD tuner's program, which I have set to use the Nvidia Purevideo for both audio and video, I get a wonderful DD5.1 signal and sound to the 990. Once I start XP Media Center Edition and do my tuning under that shell, my DD5.1 goes away. So, despite all my attempts at changing settings in MCE, I have had no luck. That's where the problem lies, for OTA HD at least.

Hmmm... You're unraveling more and more of the mystery, though. Somehow MCE is killing the DD. How rude. I haven't found anything yet on how to prevent this, but I'll poke around a bit more and see what I can come up with.

I don't know if it's relevent...
but what version of Windows media player are you running ?
Version 11 is a lot more powerful than the previous...
and does recognise DD...

Laventura:

I am using WMP 10 because 11 caused so many issues with my system. Lots of crashes, DRM issues, etc. It wasn't worth the upgrade. If I can't find another solution, I'll re-install it and see if that works. Thanks.

WMP 11 makes no difference. I need some way to force MCE to use the Nvidia Audio decoder, and I haven't found that yet.

Hi Fatawan,
i would suggest you look at some other kind of player...
altough I like the Windows media player for music...I rarely used it's video capabilities...
I always found it jittery ..or with less than
a stellar picture
when I used to watch movies from the pc I used Nero Showtime...or the ATI dvd player...both read and passed DTS-ES and DD EX without a hitch...
I also had a few other players...one by Cyberlink(Power DVD) and one by Asus(ASUS DVD) both were from bundled OEM discs.
and much less perfoming than Nero...
Good luck !

Ah, heck with it. My free Vista upgrade arrived today--here goes nuthin'!

I hope that works for you...