Just found this after making my own semi-redundant post.

Just wanted to let you know, I have a Fireface 800 at home; good audio interface in the $1000 range. Can theoretically capture at 192kHz/24bit, but with a 48kHz source I think 48kHz/24bit is entirely sufficient. Up to 8 channels. So it would be a piece of cake to do a high quality "HD matrix surround" restauration; if the decoder supports it, even with symmetrical virtually noise-free cables. Don't own any decoder myself though. If anyone feels like sending me one over for testing/doing a "HD matrix surround" for them, that'd be an option.

Personally I'm using foobars "free_dsp_surround" so far, pretty satisfying to me. (although I have no direct comparison).

I also found a SurCode Pro Logic II software decoder, but haven't tried it out yet. Seems to be an "official" thing. And some people claim that it's compatible with the original Pro Logic.

Anyway, I'm not a huge fan of the "upmixing" of the surround channel. I feel the fairest way to treat it is to simply split it up to two channels without any fancy upmixing. In the end, it's supposed to be in the back. Best I can think of would be some kind of psychoacoustic modelling thingy that makes it sound like it comes from behind when it really comes from LB and RB.

Update: Unit arrived. Seems to work as advertised. See my post "Look what I just snagged off eBay" for further details.

Added some note to the first post.

Idea: would be nice to make a comparison using different surround decoders; but the best way to produce an "uncontaminated" (by various factors as different sources, D/A and A/D converters, cables etc) comparison would be to use A SINGLE source connected to various decoders that would be recorded by A SINGLE capture card.

Now, who has more than one surround decoder AND a 4ch capture card?!?

No need for a 4 channel card spoRv, simply run the 4 channels through a matrix encoder and capture the 2 channel output 

(2021-08-24, 11:24 AM)zoidberg Wrote: No need for a 4 channel card spoRv, simply run the 4 channels through a matrix encoder and capture the 2 channel output 

Why I didn't think it by myself?!?

Found another post from the gread Disclord:

Quote:when the Special Edition of The Abyss had its short theatrical rerelease, I was lucky and got to hear a 'shoot-out' between Dolby Pro-Logic in the CP-65 cinema processor, the Aphex ESP-7000, the Shure HTS -5300 and the Fosgate DSL-2. The Dolby CP-65 came in dead last and sounded so slow in its attack times that you could often hear sounds moving just slightly behind the visual action - the Fosgate, while being co-designed by Jim Fosgate, Peter Scheiber and the Tate inventor, Martin Willcocks, and supposedly having adaptable time constants that continuously varied from a fast attack time of 3ms to a slow of 25ms was also, surprisingly, slow sounding with a blurred soundstage and had a lot of dialog sibilance spill to the surround channel - it also had a front soundstage that wandered L to R based on CF content. The clear winner was the Shure HTS-5300 which sounded like a fully discrete 4-track magnetic film and not a matrix - and like the Involve Surround Master, the Shure's channel separation specs are not particularly impressive - from 15 -25db depending on direction, but the Shure engineers knew how to apply the attack/decay times, etc. to achieve such stunning results. The Aphex was just barely behind the Shure, due mostly to some minor sibilance splatter. The theater was a Dolby SR equipped theater and so did not have the capability of playing stereo surround, so we couldn't check that type of playback.

So, a consumer Dolby Stereo decoder, the HTS-5300 - a non Pro-Logic one I might add, since Shure used their own patented Acra-Vector logic system, and a completely non-Dolby licensed decoder, the Aphex, beat the 'official' CP-65 decoding system for Dolby MP encoded surround titles - and by such a wide margin that it sounded like we were comparing matrix to true discrete sound.

As "our" Dolby SDU4 use basically the same hardware of CP-65, we lost the Dolby battle...

I wonder if there are other "something"-logic based hardware decoders around, that could be up to the task...

I found these on eBay that seem interesting - on paper they have good technical features, but how they sound?

SSI Surround Sound System 4000 II - with "Dynamic logic"
NEC PLD-310 - it has a big graphic display similar to the Shure HTS-5300

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Encoding in Dolby Pro Logic II is possible but it is quite rare aside.
I do know that it is possible to encode 5.1 audio to Pro Logic II.
Many PS2, GameCube and Wii games also support Pro Logic II and even Pro Logic IIx in some cases, especially in the Wii.

I want to know what would be the best purist upmixing solution for these games. For Pro Logic II content and for Pro Logic IIx content.
It would probably still be Pro Logic II and IIx decoders. And apparently, Dolby Surround Upmixer (the Atmos one) basically sounds the same as Pro Logic IIx if you turn off the height channels, but I am not sure about this.
Many remasters of 6th gen games and Wii games somehow keep bungling up the surround sound.
- Final Fantasy X/X-2 HD Remaster is stereo-only in all platforms even if the original PS2 versions supported Dolby Pro Logic IIx with Dolby Digital EX FMVs.
- Sonic Colours: Ultimate was only 5.1 when the Wii version was in Dolby Pro Logic IIx. The Legend of Zelda: Twilight Princess HD and Skyward Sword HD were only in 4.0 quadraphonic on Wii U and Nintendo Switch, respectively, when the original Wii versions (and GameCube for Twilight Princess) were in Dolby Pro Logic IIx. At least the surround sound is discrete this time.
- Resident Evil 4 doesn't have surround sound on any of the HD console versions (PS3, PS4, Xbox 360, Xbox One, Nintendo Switch) even if the Steam Ultimate HD Edition they were based on had discrete 7.1 surround while the GameCube, Wii and PS2 versions supported Dolby Pro Logic IIx.
- Bully: Scholarship Edition was a multiplatform release on Xbox 360, Wii and PC; the Xbox 360 and PC versions were only in 5.1 while the Wii version was in Dolby Pro Logic IIx. If it's any consolation, though, the PC and Xbox 360 versions did have discrete surround.

QSound (most famously used in Capcom arcade games but first used by Madonna in The Immaculate Collection) is a 3D spatial speaker sound technology made for stereo speakers, but it apparently sounds really great decoded to quadraphonic, so I want to know what would be a great decoder for quadraphonic matrixed audio.
But considering how it is 3D spatial audio, it would probably be better to use Dolby Surround Upmixer, DTS Neural:X and/or Auro-2D Surround.

It would also probably be great to upmix OpenAL Soft 3D audio PC games to 3D audio, since OpenAL Soft does not support outputting in Dolby Atmos and other 3D audio formats other than Ambisonics which need to be decoded with expensive software. The best compromise would be to output in the highest Ambisonics with a free decoder for 7.1 surround. It would then be upmixed with Dolby Surround Upmixer, DTS Neural:X or Auro-2D Surround. You can get real 3D audio with earphones but not speakers, even if speakers would theoretically give a better experience.
I would love to play

Just use neural-x. Any "pure" solution like integrating a DPLII decoder into your setup is not worth the hassle.
DSU isn't the same as DPLII, but like neural-x it's good enough (though I prefer neural-x). I'm curious if anyone here has experience upmixing DS and DPLII content with Auro3D, curious to see how it would work out.