For what it's worth, DTS ES Discrete is something of a special case - ES discrete must be decoded that way. DTS 5.1 can be decoded as straight DTS, DTS+Neo:6 (formerly called DTS-ES matrix), or DTS+PLIIx.

Yeah DTS-ES is the best format out there. Too bad more DVDs don't have DTS-ES. I would be happy if HDD or BD would have this format.

Blu-ray and HD-DVD will both support DTS-ES, but I doubt they'll use it much - DD+ and DTS-HD should both be superior formats. Of course, we can use DTS-ES now (happily decoding that SPDIF bitstream) without having to jump through hoops and stand on one leg just so like we're being asked to do to use the new formats...

I know this is kind of an old thread, sorry to resurrect it But this still occurs to me and is kind of annoying. I’ll be watching a high-def program and I’ll set the 990 to “Dolby Digital”. Then somewhere down the road, I’ll be watching another high-def program (with Dolby Digital) and just for the heck of it I’ll hit the “Dolby Modes” button to display on the front of the 990 what the current processing mode is and it’ll say “Dolby Pro Logic”. I can then hit the “Dolby Modes” button again and it easily switches to “Dolby Digital”.
I never specifically ask the 990 to use “Dolby Pro Logic” ever, when watching TV if “Dolby Digital” is an available surround mode. So why does it sometimes revert to “Dolby Pro Logic” and I constantly have to keep flipping it back?
The annoying part is that every channel I flip to I have to check the surround mode on the 990 to ensure I’m processing in “Dolby Digital”.

Here's something to keep in mind: not all HD material broadcasts in Dolby Digital 5.1. In fact, a surprisingly large amount of it broadcasts in Dolby Digital 2.0 - plain old stereo, just using Dolby Digital encoding. The 990 treats these two as distinctly different entities and remembers different decoding modes for them.

If the display only says "Dolby Pro Logic," then it is applying Pro Logic processing to a Dolby 2.0 signal. Applying Pro Logic to a 5.1 signal would require 7.1 speakers and would show up as "Dolby Digital+Pro Logic IIx." Based on that, it sounds to me like the 990 is doing what it should: decoding Dolby 5.1 as it should (with no additional processing) and applying additional processing to Dolby 2.0 (likely based on the "default mode" specified in the input menu).

Here's a trick I use to tell Dolby 5.1 sources from Dolby 2.0 sources. The front panel of the 990 has separate indicator lights for "SUB" and "LFE" near the bottom middle of the speaker cluster on the left. If the LFE indicator is lit up, then I've got a ".1" signal. If it isn't lit up, then I've got a ".0" signal that is probably only 2.0.

Yeah, I understand the defaults based upon the source signal (5.1, 2.0, whatever). I guess I don't understand why I constantly have to re-switch it to "Dolby Digital" when it is available. The key is that "Dolby Digital" is available, just not set to it. I was under the impression that the 990 would remember my last selection for a given source signal (5.1, 2.0, whatever). I have done it over and over and over for months, and still flip to some channels and it is back on "Pro Logic Movie" and I know "Dolby Digital" is available because if I select "Dolby Modes", I can cycle it to "Dolby Digital". It seems like at some point I will have set all defaults to "Dolby Digital" when it is available (and Pro Logic Movie when not), but I've never reached that point.

Maybe I'm doing something wrong.

"Dolby Digital" would be available with a Dolby 2.0 source because it is still a Dolby Digital signal, but it's going to be treated different from a Dolby 5.1 signal because people are likely to want different modes applied to each. As to why it keeps reverting to Pro Logic for Dolby 2.0, my only guess is that it is using whatever the input menu's default mode is set to.

For TV viewing, you may will be happiest letting Pro Logic II help out with Dolby 2.0 sources - many will contain matrix cues that are specifically intended for Pro Logic II to decode. That may be my personal preferences prodding at my keyboard, though, as that is what I prefer to do.

So maybe it is a Dolby 2.0 source and defaulting to Pro Logic. Gotcha.
If that is the case, and I then flip the 990 to "Dolby Digital", I guess the 990 doesn't automatically retain that default? In other words, it won't remember that I want Dolby 2.0 sources processed as "Dolby Digital" rather than Pro Logic?
I'll try checking the input menu's defaults. I just never did before as I thought selecting a decoding option automatically updated the default for that input.

If I understand correctly, my 990 behaves the same way as jrlouie's. Here's an example. ESPN-HD broadcasts in DD 5.1. ABC-HD usually broadcasts college football games in DD 2.0. I start off on ESPN-HD and the 990 correctly goes to Dolby Digital mode. I then flip to ABC-HD and the 990 stays in DD mode. Wanting surround sound, I select DD+PLIIx. I then switch back to ESPN-HD and the 990 stays in DD+PLIIx mode instead of going back to just DD. I change the setting then have the same issue when I change to ABC-HD.

Watch that LFE indicator on the front panel - if it's not lit when you have a Dolby Digital source (which would be indicated by the "Dolby Digital" segment on the front panel), then odds are you have a Dolby 2.0 input.