DPLII Upmix to 5.1

[Doctor M]

Back in 2010(?!) I started a thread on OTF about how to upmix stereo tracks to 5.1.  A lot of the stuff in it are now out of date and would probably take a lot of work and installing of old software just to pull off.

Does anyone have a more modern (and better quality) way of doing that now?  SurCode is the only thing I have found that may do the job and it is not cheap.

I've been contacted by someone who wanted me to listen to their upmix and give my opinion and I'm hoping to provide a better answer then: leave it stereo and let the AVR do the work.

Edit: Back when I wrote that guide, there were details of how DPL was mixed that made matrixing the channels easy.  It's largely gone from the internet.  The only thing I've found is this: https://dvedaa.github.io/posts/gsoc-2020/
And it's weird.  I'm not sure I trust the channel mapping for DPL2's surround channels.

That said, I'm working on a cunning plan to make this easy as heck for anyone needing to do this.

Edit 2: Going back to a 2010 version of Wikipedia's Dolby Pro Logic page yielded what I was looking for... and yeah that other page's DPL2 surrounds don't coincide.



Edit 3: Ah, heck. That's what I used originally for my matrces, but it was later changed to this:
https://en.wikipedia.org/w/index.php?tit...g_matrices
then this:
https://en.wikipedia.org/w/index.php?tit...g_matrices
Then removed. My head hurts.

[spoRv]

AFAIK, these matrix coefficients are the right ones.

And never read about something completely different like the ones found here: https://dvedaa.github.io/posts/gsoc-2020/

The main problem is that all the free encoders I'm aware of use the 180° phase inversion - hence, both left and right surround are in opposite phase of the front channels, while the surround left should be -90° and surround right should be +90°.
Usually there are not big differences, but for example when a circular pan happens, the +180° approach fails to reproduce it correctly.

[Doctor M]

Yeah, I was thinking of working out an ffmpeg pan string that would do this job, but it might be time to revisit my original thread. It did use a filter that SUPPOSEDLY included a DPLII decoder.
I always expected there would be more options by now, but there doesn't seem to be.

[Wisp of Smoke]

The other key part of a DPL-2 decoder is the logic control action. Assigning the channel layout is one thing, but the logic - steering part of the decoder is just as critical.

DPL-2 is the last of the wide band decoders as implemented by matrix legend Jim Fosgate. All of the newer digital decoders use multi-band decoding. These include Neural X, Dolby DSU, and DTS X. Sometimes multi-band can be superior. Other times not. Each of these decoding systems will differ on how aggressive they steer sounds - how many bands per channel and so on.