I have a 990 which I've enjoyed thoroughly for the past few years. I was doing some research on Dolby TrueHD and PLIIx and found that the higher Denon models (and perhaps the Onkyos) can matrix the 5.1 from a TrueHD to 7.1, much like how the 990 does "Dolby Digital + PLIIx."

Will the 997 be able to do this?

Well, we don't know anything for sure, but personally I would expect the 997 to be able to use Pro Logic IIx in conjunction with most any 5.1 source (Dolby Digital, DTS, DD+, TrueHD, DTS-HD HR/MA, or 5.1 PCM). Depending on what they do with DSD bitstreams, that might not be able to work with PLIIx - if it goes DSD straight to the DAC, it would be impossible, but if it went DSD-to-PCM it would be an option.

This ability was rare on early HDMI receivers due to processing requirements, but there are a lot of receivers now that can do it.

We know that the SN Receiver will not matrix 5.1 TruHD and Master audio into 7.1. Do you think the 997 will not be able to as well? That would be a huge issue. (The SN will matrix everything but the above)

I hadn't heard about that limitation - is that the Sherwood R972 that has the limitation, or is it the R872?

The R972 has that limitation. I found it surprising as well, but I have confirmed it via email with Sherwood.

Interesting. I wonder if it's something they plan to adjust via firmware update, or if it is a result of the processing requirements imposed by Trinnov? It sounds like it will still matrix 5.1 PCM, though. Right?

I'm guessing it's a processing limitation. I know Emotiva made a change to their UMC design to add second dual-core processor so they could do full post-processing at 192/24, which apparently wasn't possible with the single processor. In most cases, systems that use dual processors (including the 972/997), the decoding of the HD audio is done on one chip, and then any post-processing is handled on the second chip. My guess is that the Trinnov processing is enough of a hog that there isn't enough processor horsepower left over for additional post-processing (i.e. PLIIx).

I think there may be a possible work around, which is to truncate the HD audio down to 96/24, which apparently many manufacturers are doing so they can apply post-processing on the lower-end chips.

Interestingly, if you've followed the Cary 11a fiasco, it appears that when the units originally shipped, it wasn't possible to apply post-processing to the HD codecs, but a recent firmware upgrade has made that possible. Not sure exactly what Cary did to allow it, but I suspect there's some sort of monkey-business going on in the background.

From the emails I have been having it seems that it will matrix 5.1 from all sources except TrueHD and Master audio (both bit streamed and PCM over HDMI). Trinnov can be applied to any of the sources that are available if in the future they can update it via firmware (I also inquired about the firmware upgrade and did not get an answer yet).

So it won't do matrix processing on TrueHD or DTS-HD MA sources that are decoded externally? That sounds sort of odd, as the external decoding would create a multichannel PCM signal that's going to be functionally indistinguishable from any other externally decoded HDMI input. Sounds curious...

Yes, it does sound odd. That is what I have received back via email though, twice. What could cause that issue?