I tried watching a video clip with an AC3 3/0 track (L+C+R with no LFE). Regular Dolby mode worked fine, but selecting PLIIx mode would only expand the L+R channels to all 7 speakers (center channel was disgarded). This, of course, resulted in no dialog. Is this a limitation of Dolby PLIIx, or a bug in the 990's software? Can anyone else confirm this?

I recall a rather lengthy debate earlier about Pro Logic IIx in relation to another product, in which it was said that PLII and IIx were only required to work with Dolby 2.0 and 5.1 sources. Having said that, though, I'm also not sure how many times a 990's been fed a Dolby Digital 3.0 signal - it's very possible that the 990 could apply PLIIx without losing the dialog even though it isn't technically required that a PLII/IIx processor be able to do so, and that what you're encountering is a previously-unknown bug. I'd try confirming it in my system, but I don't have any material in my library with a Dolby Digital 3.0 audio track - where did you come across one?

The video file is an HD capture of the TV show "Heroes" pilot. This is the only time I have seen a 3.0 audio track (I'm not sure why it's not 5.1). It took me a couple of seconds to figure out how I was hearing all the sound effects but no dialog! Very strange.

I would think it would be fairly trivial to simply pass through the center channel on a 3.0 (or greater) signal. Virtualize missing channels, but leave existing channels alone?

Hmm... I may need to see if it'll be repeated in HD in my area. I can't record HD, but I can perhaps catch it as it broadcasts and see what my 990 does. For that matter, if you had the capability of sharing at least a piece of the episode (maybe just a couple minutes with the audio track intact) - that would probably be handy for Outlaw if they want to test it.

I can extract a small portion of the file, but does Outlaw have a computer setup to play Transport Streams for testing? I could probably convert it to DVD if necessary.

Outlaw may. I don't, and unfortunately the repeats run on USA (so no HD). I will try to flip over to the local HD broadcast next Monday to see what they're doing.

Ok, I just found another strange PLIIx issue. I just had DISH installed today and was testing my setup. I had it on 9477 with the documentary "Hard Water" playing. INFO says it has a DD 5.1 soundtrack. Playback in regular Dolby 5.1 mode confirms this. If I switch to PLIIx Movie mode, then it loses the left and right side channels, but the rear left and right playback just fine (so basically it is just switching the side surrounds to the back surrounds). If I switch to PLIIx Music mode, then all 7 channels work.

I'm gonna call Outlaw support and report these issues.

I think it may be a limitation of PLIIx.

One thing to keep in mind is that the PLIIx circuit always sees only 2 input channels. When fed a 2-channel source, it sees 2 main channels and expands them out to 7 outputs. When fed a 5.1 or 6.1 source, it sees 2 surround channels and expands them to 4 outputs. Obviously it sees the 2 channels in context and knows when to adjust the processing.

2-channel material has correlated (in-phase) and decorrelated (out of phase) sounds. The correlated info is extracted and sent to the centre speaker; the decorrelated info is sent to the surrounds.

With 3-channel material, there is rarely any correlated information in the L/R channels. Anything that was supposed to image in the centre of the soundstage is in the discrete centre channel already, not mixed as dual-mono in the L/R channels like with 2-channel recordings.

So, when the PLIIx circuit is fed a 3-channel signal, think about what happens. It sees 2 channels (left & right) and extracts centre and surround info. In this case, there is no correlated info in the L/R channels, so the centre output is... you guessed it, silence. Decorrelated info still gets extracted and goes to the surrounds. First a bit o'background: old Dolby Surround mixes start off as 4 channels (left, centre, right, and a mono surround channel). These are then matrixed down to 2 channels for stereo compatibility. However, upon playback, you can use Pro Logic decoding to get back the original 4 channels (the mono surround channels is sent to both surround speakers).

When discrete multi-channel technology came to home video, those 4 stems from old soundtracks could be delivered as discrete channels instead of squashing them down into a 2-channel matrix. The mono surround channels was simply copied to both surround channels of the 5.1 soundtrack. For 5-speakers set-ups, this isn't a problem.

However, if you have a 7.1 set-up, it can be a problem. Processing such as EX, ES and PLIIx work the same way a centre channel is extracted up front. Sounds that are common to both surround channels are extracted and sent to the speakers behind you. This is where they would have phantom imaged anyway. These sounds are also actively cancelled from the L/R side speakers (you don't want rear sounds coming from behind you and at your sides). The leftover stereo information remains in the side speakers.

'Hard Water' probably has the same mono information in both surround channels. When played back in the normal DD mode, the surround information gets sent to the speakers at your sides. When you apply EX or PLIIx processing, it grabs common information (in this case it grabs everything) and sends it to the speakers behind you. It also cancels that information from the sides (in this case it cancels everything). End result, no sound from the sides, everything coming from behind you. For 5.1 sources, the PLIIx Music mode has one difference from the Movie mode: the extracted rear information is not cancelled from the sides. For movies, Dolby apparently wanted to emphasize rear-versus-side separation. For music, the processing emphasizes rear-and-side envelopment. When watching 'Hard Water' with the PLIIx Music mode, rear info was extracted but not cancelled from the sides. End result, same sound from all 4 surround speakers.

Hope all of that made sense.

Yes, it does make sense. Thanks for the Dolby lesson! It seems PLIIx could use a logic upgrade to better handle these kinds of situations. Maybe Outlaw can add their own code to get around these limitations?

Dolby 3.0 + PIIx = always add original center channel back into the mix

Enemy,

I had decoding issues as well with my 990.

What solved it for me was plugging the 990 into the "Digital" power outlet in my monster HTS-3600 (I think that's the model number, not near it at the moment...).

If I plug it into another port, I'll start getting DD decoding issues. EXACTLY what you describe with...

"Ok, I just found another strange PLIIx issue. I just had DISH installed today and was testing my setup. I had it on 9477 with the documentary "Hard Water" playing. INFO says it has a DD 5.1 soundtrack. Playback in regular Dolby 5.1 mode confirms this. If I switch to PLIIx Movie mode, then it loses the left and right side channels, but the rear left and right playback just fine (so basically it is just switching the side surrounds to the back surrounds). If I switch to PLIIx Music mode, then all 7 channels work."

EXACTLY. I swear, a good power filter and it cleared up for me. I called monster and they stated that the "Digital" is the most filtered, followed by the Analog, and down from there...