[pinnahertz]

Great info. Just to clarify myself: I'm using "Dolby Surround" to broadly refer to non-consumer/cinema formats, while "Pro Logic" encompasses the consumer-facing stuff of the late 1980s (1987 sounds right but may not be).

Dolby's cinema surround format was called "Dolby Stereo", which was immediately confusing because it could be used for LCR only, surround was optional and not always mixed in. Dolby Surround was in fact a label attached to the earliest of consumer surround decoders in 1982. I've forgotten the manufacturer that first licensed the Dolby Surround logo for consumer use, but it may come to me. I had one for a while.  It had no steering, but did have modified Dolby B NR on the surround channel plus adjustable surround delay and volume.  
 
The Dolby Surround logo appeared in the opening of some TV shows like The Tonight Show that were mixed for the consumer decoders without steering. That went on for five (long) years until 1987 when ProLogic was introduced. I still have the T-shirt they handed out with a block diagram on it. The Dolby Surround label was never meant for cinema use AFIK. Cinemas with 70mm magnetic capability marqueed "Dolby 6 Track Surround" or something like that. Few releases, only big ones, but 70mm mag with Dolby A, then later SR just befor Dolby Digital was pretty darn good. Discrete channels, decent dynamics.

I know that, technically speaking, Dolby has re-used "Dolby Surround" as a brand for many things, even including digital multi-channel, and frankly I find it unnecessarily confusing on their part. I do know that on VHS, for example, some are labeled as "Dolby Surround" to refer to Pro Logic compatible matrix encodes, but that audio track is not necessarily what was in theaters in the 1970s or 1980s, nor is the equipment decoding it directly comparable to what was in theaters either.

Yes, Dolby is one of the masters of brand confusion. Dolby Surround on any consumer format was actually just a dub of the LtRt master, though. They didn't remaster for the home market at all. That was on VHS, Beta HiFi, and LaserDisk (both digital and AFM). ProLogic was directly compatible with the cinema version, which eventually upgraded their old Cat.150 cards to similar performance devices. There was only one encode matrix for Dolby Stereo (meant for steered decoders) and Dolby Surround (meant for non-steered decoders). It was just a question of what decoder you monitored your mix with.
 
The funny thing about that was when the first stereo audio tracks appeared on LaserDisc (predated Beta HiFi and VHS HiFi), some of us "discovered" there was hidden surround. I confirmed my suspicion with a friend deep in the industry, who tipped me off to how it all worked.  I purchased a Dolby CP50 manual and studied the schematics.   I built my own surround decoder just about the same time as the first commercial decoder was being designed.  I still have a few of the PC boards dated 1980.  

Pro Logic II is, as I understand it, an entirely distinct development, designed by Fosgate Labs and licenced over to Dolby; you're 100% that it will take the Dolby Surround/Pro Logic I matrix input and unpack it "correctly" for backwards compatibility, but the actual DPL-II matrix looks a bit different, one of the biggest changes is that the surround channels are discrete (it actually provides 5 channels out). And as you pointed out, channel separation is meant to be higher.

The only difference is in the Ls and Rs extraction from LtRt tracks, which is somewhat ambiguous in fact because tracks aren't actually encoded that way. Remember, there was only ever one encode matrix to create LtRt masters. The PLII decode matrix has to be different for the L/R extraction, but it's an extraction with assumption. They had to still allow for legacy decoding.

However for actual "1980s content" I'm not sure if this makes much of an appreciable difference.

PLII is a consumer product, and part of the reason for the Ls/Rs extraction from LtRt tracks has to do with home systems have few, usually only two, surround speakers that don't provide the diffuse surround field the tracks are mixed for in large cinemas (with a dozen or more surround speakers). THX did it first in Home THX with surround decorrelation, which was not a LsRs extraction, but rather made Ls and Rs dissimilar so they couldn't be localized to the speakers as well. That and dipole surrounds did a fine job of replicating a diffuse surround field.
 
PLII actually does a better job decoding a 1980s LtRt track in the home. Home systems are different from large theater systems in several ways, like I just said. But nothing is/was ever specially encoded for PLII in an LtRt track. PLII made provision for other extractions as well, like 7.1 from 5.1. But again, it's an ambiguous approximation because the home 7.1 speaker plan is different from the theatrical one, and no 5.1 theatrical track was ever specifically mixed for the home format. It works because of the size and limited speakers in the home. Dolby has done other channel extractions, as did THX with their modification to the 7.1 home plan, then added a different 7.1 caming plan.
 
If we thought Dolby were masters of market confusion then THX would be the Jedi Masters of marketing confusion, which has spelled their demise.

 

[pinnahertz]

I remember dolby pro logic for surround sound for analog television broadcasts. But that doesn't have relevance today. And there are so many codecs and interfaces that support surround sound, so matrix decoding is not necessary for surround sound. Dolby pro logic and dolby headphone are separate technologies, you don't have to use them together, even with 2 channel input. There actually were minidisc players that just had dolby headphone, and used it as a stereo crossfeed. A crossfeed is anything that at a minimum, mixes elements on a delay to represent itd. Since dolby headphone does that, it is a crossfeed.

You have several things confused here.  ProLogic wasn't broadcast on analog television at all.  ProLogic is a decoding system for extracting LCRS surround from a two-channel soundtrack. You don't broadcast or record in ProLogic. 
 
When you say ProLogic doesn't have relevance today you are excluding all movies with Dolby Stereo soundtracks from 1977 until well into the 1990s.  The first Dolby Digital film ("Batman Returns") was released in selected theaters in 1992.  Dolby Digital didn't enter the consumer world until 1995, on LaserDisc ("Clear and Present Danger").  So between 1977 and 1992, any film released in Dolby Stereo that was not also released in 70mm magnetic or Dolby Digital would only have an LtRt surround track, and would therefore have to be decoded with ProLogic. That's at a minimum 15 years of surround movies you've labeled irrelevant. Probably more as not every surround film after 1992 was distributed in Dolby Digital, and 70mm all but vanished by the mid 1990s.
 
Additionally, TV sound between 1984 (first stereo broadcasts) and the advent of DTV in 2008, all TV had was two-channels of audio.  TV programs that included surround were encoded into an LtRt track, and would be decoded with ProLogic.  That's 24 years of programming that you've just labeled irrelevant. 
 
So many codecs?  Hmm.. not really.  For TV, there's one: Dolby AC3, otherwise known as Dolby Digital.  For DVD there were two, Dolby Digital and DTS. Dolby Digital won, making it pretty much the default.  We're at one codec, if you're counting.   With Blueray we got high resolution audio in the form of Dolby TrueHD and DTS Master Audio.  DTS is winning that one, but Blueray isn't winning much market share.  DVDs still outsell BDs by quite a margin, so that makes TrueHD and Master Audio two minor codecs.  Because most BD players in the world and many AVRs can't handle these codecs, they really are very minor players.  The default track on BD is good old Dolby Digital.  So our count now is 1 plus 2 minor ones.  Streaming seems to not be grasping hold of TrueHD or Master Audio very quickly, so they still are a non-factor.  
 
Did I hear someone say "Atmos"? Well, the base track for Atmos is TrueHD, which it has to be there or non-Atmos systems don't get an HD soundtrack.  Atmos has not penetrated the home market much at all, and it's technically an add-on to an existing surround codec, so let's not even count it. And there's the good old Dolby Digital track on a BD anyway for the greater majority who can't manage the HD tracks.  
 
Our count is stuck at 1 codec plus 2 minor codecs and one esoteric immersive format (Atmos).  
 
PCM, you say? Sure, but you won't find it streamed, or on disc as a surround track.  It shows up in games.  But we're talking about tracks that might need ProLogic, and I don't think that was ever games, so we don't need to talk about PCM. 
 
I don't call 1 codec plus 2 minor codecs "many codecs". 
 
Now, "many interfaces that support surround sound".  Many?  HDMI, Coax/SPDIF and Optical/SPDIF.  That's 3, two of which are identical except for the cable type, so make that a big round 2 interfaces that support surround sound.  Analog? Yes, you can do that, but the days of disc players with 6 analog jacks are gone.  The days of streamers with 6 analog jacks never occurred.  That makes analog a computer interface only.  Do we count it?  
 
You're confused about Dolby Headphone.  This is a technology that uses HRTF to render surround tracks in the intended perspective when listened to in headphones.  The tracks can be 5.1, 7.1 or matrix 2 channel (like you would decode with ProLogic).  You stated that ProLogic and Dolby Headphone are two separate technologies that don't have to be used together.  This is incorrect.  For Dolby Headphone to work it must be presented with surround information.  For a two-channel source, that is extracted with ProLogic.  You do have to use them together.  Dolby Headphone is far more than crossfeed.  Using Head Related Transfer Function information it can place surround channels behind and to the side, just as an example.  Crossfeed is a very rudimentary (and ineffective) attempt at getting two channel stereo out from the middle of the head.  The two are nothing alike. 
 
A form of Dolby Headphone processing was included on some Minidisc player, but the purpose was different: to synthesize a virtual surround field as opposed to render a 5.1/7.1 or ProLogic surround field to headphones.

 

[mindbomb]

  You have several things confused here.  ProLogic wasn't broadcast on analog television at all.  ProLogic is a decoding system for extracting LCRS surround from a two-channel soundtrack. You don't broadcast or record in ProLogic. 
 

I never suggested prologic was anything other than a matrix decoder. Now, this might be hard to appreciate for people accustomed to all the fancy features of digital television, but matrix decoders like pro logic were a big deal for analog television broadcasts. The shows that were compatible with it would have a graphic to tell you to turn on your decoder. You ended up being able to get surround sound through the low bandwidth of analog television audio, which was pretty impressive for the time.
 
Quote:

 
When you say ProLogic doesn't have relevance today you are excluding all movies with Dolby Stereo soundtracks from 1977 until well into the 1990s.  The first Dolby Digital film ("Batman Returns") was released in selected theaters in 1992.  Dolby Digital didn't enter the consumer world until 1995, on LaserDisc ("Clear and Present Danger").  So between 1977 and 1992, any film released in Dolby Stereo that was not also released in 70mm magnetic or Dolby Digital would only have an LtRt surround track, and would therefore have to be decoded with ProLogic. That's at a minimum 15 years of surround movies you've labeled irrelevant. Probably more as not every surround film after 1992 was distributed in Dolby Digital, and 70mm all but vanished by the mid 1990s.
 
Additionally, TV sound between 1984 (first stereo broadcasts) and the advent of DTV in 2008, all TV had was two-channels of audio.  TV programs that included surround were encoded into an LtRt track, and would be decoded with ProLogic.  That's 24 years of programming that you've just labeled irrelevant. 
 
 

When these movies or tv shows are re-released in modern formats, like dvd, bluray or streaming, the audio is generally just converted to discrete surround sound. I feel odd having to explain this. I thought it was pretty self evident that people are able to enjoy this content with surround sound without using a matrix decoder.
 
 

  So many codecs?  Hmm.. not really.  For TV, there's one: Dolby AC3, otherwise known as Dolby Digital.  For DVD there were two, Dolby Digital and DTS. Dolby Digital won, making it pretty much the default.  We're at one codec, if you're counting.   With Blueray we got high resolution audio in the form of Dolby TrueHD and DTS Master Audio.  DTS is winning that one, but Blueray isn't winning much market share.  DVDs still outsell BDs by quite a margin, so that makes TrueHD and Master Audio two minor codecs.  Because most BD players in the world and many AVRs can't handle these codecs, they really are very minor players.  The default track on BD is good old Dolby Digital.  So our count now is 1 plus 2 minor ones.  Streaming seems to not be grasping hold of TrueHD or Master Audio very quickly, so they still are a non-factor.  
 
Did I hear someone say "Atmos"? Well, the base track for Atmos is TrueHD, which it has to be there or non-Atmos systems don't get an HD soundtrack.  Atmos has not penetrated the home market much at all, and it's technically an add-on to an existing surround codec, so let's not even count it. And there's the good old Dolby Digital track on a BD anyway for the greater majority who can't manage the HD tracks.  
 
Our count is stuck at 1 codec plus 2 minor codecs and one esoteric immersive format (Atmos).  
 
PCM, you say? Sure, but you won't find it streamed, or on disc as a surround track.  It shows up in games.  But we're talking about tracks that might need ProLogic, and I don't think that was ever games, so we don't need to talk about PCM. 
 
I don't call 1 codec plus 2 minor codecs "many codecs". 
 
Now, "many interfaces that support surround sound".  Many?  HDMI, Coax/SPDIF and Optical/SPDIF.  That's 3, two of which are identical except for the cable type, so make that a big round 2 interfaces that support surround sound.  Analog? Yes, you can do that, but the days of disc players with 6 analog jacks are gone.  The days of streamers with 6 analog jacks never occurred.  That makes analog a computer interface only.  Do we count it?  
 

When I saw this, I had to do a double take and see if we were in the computer audio section. Yes, there are many codecs that support surround sound. Some of the big ones being flac, opus, and aac, in addition to the proprietary one for movies, but there are a lot of obscure ones also. And to suggest all of these are uncommon is very surreal in the context of arguing for the importance of dolby pro logic. And the bluray of Kill Bill, for example, does have pcm as the surround track, so it's not impossible to find examples of that, though it is increasingly rare as it is a waste of space.
 
Many interfaces do support surround sound. There are ubiquitous hdmi and usb ports of course, but what you are essentially asking is for ways to transfer a certain amount of digital data, which can be innumerable. You can do it with pci express, wifi, displayport,firewire,madi, etc. And again, you are bringing this up in the context of arguing for prologic, which makes no sense. Hdmi is much more widespread than hardware matrix decoders nowadays.
 
 

  You're confused about Dolby Headphone.  This is a technology that uses HRTF to render surround tracks in the intended perspective when listened to in headphones.  The tracks can be 5.1, 7.1 or matrix 2 channel (like you would decode with ProLogic).  You stated that ProLogic and Dolby Headphone are two separate technologies that don't have to be used together.  This is incorrect.  For Dolby Headphone to work it must be presented with surround information.  For a two-channel source, that is extracted with ProLogic.  You do have to use them together.  Dolby Headphone is far more than crossfeed.  Using Head Related Transfer Function information it can place surround channels behind and to the side, just as an example.  Crossfeed is a very rudimentary (and ineffective) attempt at getting two channel stereo out from the middle of the head.  The two are nothing alike. 
 
A form of Dolby Headphone processing was included on some Minidisc player, but the purpose was different: to synthesize a virtual surround field as opposed to render a 5.1/7.1 or ProLogic surround field to headphones.

The dolby prologic II upmix is optional for dolby headphone. However, even if it wasn't, you could always foil it by padding your audio with silent channels. You can just use dolby headphone on 2 channel audio. I don't see what is so hard to grasp about this conceptually. If it can emulate a surround sound system with 5.1 audio, then obviously it can emulate a stereo system with 2.0 audio, since that is a subset of the surround system.
 
Dolby headphone might be doing more than your average crossfeed, but that doesn't mean it isn't a crossfeed. The minidisc players that had dolby headphone are an example of both these things. They had 2 channel input, and the goal was analogous to what a crossfeed switch on a portable amp would do - create a more natural experience for stereo music.

 

[pinnahertz]

  When these movies or tv shows are re-released in modern formats, like dvd, bluray or streaming, the audio is generally just converted to discrete surround sound. I feel odd having to explain this. I thought it was pretty self evident that people are able to enjoy this content with surround sound without using a matrix decoder.

It's only self-evident if you ignore the details.
 
Yes, some LtRt tracks are released as discrete 5.1 (actually 4.0) tracks, but it depends on what material is in the vaults and who is doing the release. The major films usually had vaulted LCRS magnetic masters, and if released in 70mm, may even have had 6 channel sound in some form going back to the 1950s (different channel plan then, though). But there is a huge library of films that were released in Dolby Stereo with the best, often only surviving sound master being LtRt. If  those films are  released in something other than matrix surround it's only because the decoding was already done, and it was equivalent to ProLogic.  I have a number DVDs with matrix surround that must be decoded with ProLogic. Overall, it's not a small number, though clearly not important to everybody.
 
ALL stereo TV programs mixed for surround up to the advent of DTV have LtRt tracks and if released, even remastered, a great many retain LtRt. We've been watching a recently released HD remaster of a sitcom that had matrix surround...and it still does, and it's streamed that way.  I have surround status return on my HT control system and always check to see what method it has chosen.  I still see a lot of "Stereo", which I then force to ProLogic, and quite a bit just directly triggers ProLogic. Then there's the idiotic choice of encoding a matrix surround track as Dolby Digital 2.0, which precludes forcing ProLogic (at least on my AVR). Happens all the time. To be fair, it's mostly Dolby Digital done right, but not 100% by any means.

When I saw this, I had to do a double take and see if we were in the computer audio section. Yes, there are many codecs that support surround sound. Some of the big ones being flac, opus, and aac, in addition to the proprietary one for movies, but there are a lot of obscure ones also. And to suggest all of these are uncommon is very surreal in the context of arguing for the importance of dolby pro logic.

Look at the number of releases in any of those other codecs then compare that number to the number of releases in matrix surround and Dolby Digital.  Then check the number of units sold of those releases.  That's my point.
 

And the bluray of Kill Bill, for example, does have pcm as the surround track, so it's not impossible to find examples of that, though it is increasingly rare as it is a waste of space.

PCM up to 6 channels can even be on a DVD, but it usually isn't. It's not used by anything but a tiny fraction of users. Everything defaults to Dolby Digital or DTS, so if you want to choose PCM you have to take a trip through a setup menu.  
 
You can cherry-pick obscure examples all day, it doesn't change the fact that the overwhelming mass of content is in just a very few codecs. 

Many interfaces do support surround sound. There are ubiquitous hdmi and usb ports of course, but what you are essentially asking is for ways to transfer a certain amount of digital data, which can be innumerable. You can do it with pci express, wifi, displayport,firewire,madi, etc. And again, you are bringing this up in the context of arguing for prologic, which makes no sense. Hdmi is much more widespread than hardware matrix decoders nowadays.

It doesn't matter what the interface is, it matters what the content is. My point was that calling ProLogic irrelevant today is at very least narrow minded and short sighted.
 
But regardless, look at the number of surround systems and the interface used from the source. How many systems connect surround audio with PCI Express, Firewire or MADI? Not zero, but nothing compared to HDMI.  Most users don't even know they exist.

Dolby headphone might be doing more than your average crossfeed, but that doesn't mean it isn't a crossfeed.

Well, knowing a bit about what goes into Dolby Headphone, comparing Dolby Headphone to crossfeed is like saying a Saturn V booster is just like a bottle rocket. Yes, the both burn fuel an leave the ground, but there are a few minor differences too.  But that's just me.

 

[obobskivich]

PLII actually does a better job decoding a 1980s LtRt track in the home. Home systems are different from large theater systems in several ways, like I just said. But nothing is/was ever specially encoded for PLII in an LtRt track. PLII made provision for other extractions as well, like 7.1 from 5.1. But again, it's an ambiguous approximation because the home 7.1 speaker plan is different from the theatrical one, and no 5.1 theatrical track was ever specifically mixed for the home format. It works because of the size and limited speakers in the home. Dolby has done other channel extractions, as did THX with their modification to the 7.1 home plan, then added a different 7.1 caming plan.

If we thought Dolby were masters of market confusion then THX would be the Jedi Masters of marketing confusion, which has spelled their demise.

Great post there, and agree on "masters of marketing confusion" entirely - that it takes nearly a page of text for us to get "on the same page" when discussing something should be all the evidence one needs to say "Dolby, straighten your stuff out!" :rolleyes:

The only thing I'd add: there is actually some content that advetises itself as being "encoded for PLII" - some videogames on PlayStation 2, GameCube/Wii, and iirc Xbox, had built-in "PLII output" modes. Now, whether or not this is just Lt/Rt I'm not entirely certain, but it is meant as an analog surround output for games/hardware that don't have the ability to do Dolby Digital Live. Here's a (relatively long) list for PlayStation 2 titles, for example: https://www.mobygames.com/attribute/sheet/attributeId,206/p,7/

And to note, this is built into the game, not the hardware/console software, and is an option that has to be enabled/configured per-game.

Well, knowing a bit about what goes into Dolby Headphone, comparing Dolby Headphone to crossfeed is like saying a Saturn V booster is just like a bottle rocket. Yes, the both burn fuel an leave the ground, but there are a few minor differences too. But that's just me.

Agreed. I don't see the point in a cherry-picked semantic argument about this, and this really exemplifies that. Dolby Headphone is most frequently/commonly discussed as an HRTF feature, just like DTS Headphone:X or Razer Surround, while crossfeed is more frequently aligned with the work of Meier Audio (and many amps/devices with crossfeed licence Meier's implementation as opposed to coming up with their own, although I don't think Meier Audio maintains a list of licencees on their site, and note that I'm not saying "all crossfeed" is Meier Audio-based, just that it isn't the sole domain of the Corda series).