[Help] Dolby Surround 2.0 Matrixed files Upmix

[spoRv]

So, best way to listen to old tracks *may* be to use a Dolby Surround-only decoder, right?

[PDB]

So, best way to listen to old tracks *may* be to use a Dolby Surround-only decoder, right?

That’s why I collect them

Seriously I have no problem with stereo separation on the rears if that someone’s jam but I do like to alternate that with what would be authentic to the time.

[Chewtobacca]

So, best way to listen to old tracks *may* be to use a Dolby Surround-only decoder, right?

That's probably the best bet as far as fidelity is concerned.

[zoidberg]

So, best way to listen to old tracks *may* be to use a Dolby Surround-only decoder, right?

Maybe not necessarily the best way but definitely the most authentic. Even newer Pro-Logic II receivers can be put into original Pro-Logic decoding mode with the band-limited mono surround.
Another factor to consider is the type of speakers used for the rears, I know back in the day bipoles were recommended for the more diffuse soundfield they generate.

[deleted user]

I dunno how hardware implementations do it, but the DPLII Surcode decoder definitely ignores the bandlimiting even in the "legacy surround" mode. It also does something weird with the surrounds that looks like a phase inversion.

[Wisp of Smoke]

A few comments on DPL-1 vs DPL-2.

The Dolby Stereo matrix and to an extent the first consumer "logic" version of Dolby Stereo called Dolby Pro-Logic (DPL-1), were primarily focused on dealing with optical soundtracks and poorly produced soundtracks, as in the shortcomings that can come with that those systems.  In other words, a number of limitations were imposed on the matrix decoding, including slower response times which result in less precise decoding.

Thankfully consumers do not have to rely on optical sound as a delivery format, and things such as phase and azimuth errors are now extremely rare in digital audio delivery formats.  

With Jim Fosgate's DPL-2 design, Dolby matrix decoding took a sizable leap forward in more precise, quicker steering and better handling of multiple source image placement in the soundfield, and for me .. the best advancement was the reduction of what was often called "center channel build up" often found in DPL-1, when subtle sound effects were inadvertently pulled towards the center.  This had previously compromised complex sound mixes with DPL-1 and made upmixing of non-encoded material sound .. well.. far less than desirable.

The optional wider frequency response in the surrounds and split surrounds of DPL-2 were to me icing on the cake when compared to the advanced decoding it provided, with that being the primary enhancement. IIRC, the DPL-2 Music mode still uses a gentle high frequency roll off in the surrounds, and also disables the auto balance feature found in the movie mode and previous DPL decoders.  Auto balance is nice on poor recordings but can occasionally cause issues with soundtracks featuring directional dialog, as anything very close to being center panned can inadvertently get pulled to dead center. With the DPL-2 Music mode, just make sure Panorama is turned off.

The DPL-1 emulation mode of DPL-2 still imposes the same 7Khz rolloff and mono surrounds as DPL-1, but has the newer improved steering.

I did some house mousing and found an extensive DPL-2 article, written when the new format was just released.
https://hometheaterhifi.com/volume_8_1/d...-2001.html

The Shure 5300 was unique in that it was before DPL2, and very rare at that time period, a Pro-Logic decoder that actually had faster response times than the DPL-1 parameters.  Shure had worked with Dolby and were allowed to use the Pro-Logic logo, even though it exceeded the imposed limitations of the DPL-1 format. Along with quicker response times, the Shure utilized a 3-band decoder design that was very effective in it's steering control. 

The recent "Surround Master" decoder also used 3-band decoding, but was limited to QS and SQ quadraphonic decoding. That said, SQ is very very close to the Dolby Stereo Matrix. It's worth noting one of the best SQ quadraphonic decoders ever released was by Jim Fosgate, who also later made the DPL-2 decoding advancements in co-operation with Dolby... a nice "full circle", don't ya think?

[spoRv]

Thanks for the detailed post!

[CSchmidlapp]

Thanks everybody for another interesting thread.
The history of the technical cinema is truly amazing and all the knowledge you guys share is greatly appreciated.
My research continues

Ive found the Freesurround plug-in for Foobar2000 pretty amazing.
The documentation on it says it is 'mimicking' the prologic settings (and in turn the matrix decoding of Dolby Surround)
so it may not be the answer for purists. With the information presented above about rear channel frequency ranges ect the answer on how to best preserve the 'original' sound presentation may not lie in this software (or any).

For what I wanted its pretty spot on, and if the thread on the plug in is to be believed kind of improves on PLII ect.
The use of all the speakers in a given setup is much more aggressive than when compared with a true descrete mix with me even wondering whether i should adjust the C volume alot of the time!

This was purely for projects really, as why would I not just use the multiply options on my AV amp.
I don't think I need too explain why the option of upmixing 2 channel stereo to 5 channel is helpful for fan projects and I wiil be decoding to 5.0 and adding a custom LFE channel, (if a project requires it)

[captainsolo]

Wait...there's a PL1 standard mode on newer PLII systems? How in the world do you access that?

[Wisp of Smoke]

Wait...there's a PL1 standard mode on newer PLII systems? How in the world do you access that?

The DPL-1 mode was originally part of the DPL-2 package, including at a minimum the DLP2 Movie and Music Mode. My last receiver (circa 2012?) still included all three decoding modes. 

That said, Dolby has done a recent shift in their decoding marketing.  Dolby Atmos receivers have a generic mode simply called "Dolby Surround" that replaces DPL-2, in that, along with Dolby Atmos upmixing of 7.1 and 5.1 discrete tracks, it also does updated decoding of Dolby Stereo soundtracks to 5.1, 7.1, or Atmos speaker configurations. Rear decoding still has split surrounds like DPL-2. From what I understand, the DPL-2 decoding matrix equations are still adhered to, only the logic processing has changed. With Dolby Atmos receivers & processors, DPL-2 decoding is now optional, as in the manufacturer has to pay a little extra to include DPL2 if they want that on board as well. And a few higher processors have done just that.

If a receiver or processor does not use Atmos processing, then DPL-2 is still the default.

I have not had a chance to test a Atmos Dolby Surround decoder, and would love to throw some torture test material at it someday.