Blu-ray.com:

Scream supplies the film's original Dolby Stereo as the default (and only) track on both discs: a DTS-HD Master Audio 2.0 Stereo (1614 kbps, 24-bit) on Disc One and a DTS-HD Master Audio 2.0 Stereo (1646 kbps, 24-bit) on Disc Two.

The Shout Factory (Scream) release contains two different cuts: theatrical and desaturated (both, 2.0 stereo mix) but Laserdisc 4.0?

https://www.lddb.com/laserdisc/03235/41057/Dracula

How can that difference be possible? What is the real original Dolby stereo track? I was wondering if it would be nice to have a preservation with the LD track.

Not really sure what you're asking tbh. It's not 4.0, it's 2.0 in the Dolby Stereo matrix so will be same channel layout as Scream Factory 2.0 "stereo" tracks. That what you meant?

Basically the Dolby Motion Picture Matrix turns 4 channels into 2 for storage on a 35 mm print then when played back it gets (kinda) turned back into 4. The first home video decoding system for this was called "Dolby Surround" which is what lddb is referring to. Does that help?

Guessing the two slightly different audio tracks are simply scanned from their two respective prints.

So, will that DTS-HD Master Audio 2.0 Stereo be converted to 4 channels (left, center, right and surround speakers) in a home theater system in the same way as in theaters with a 35 mm print?

If so, why do some blu-ray releases like Platoon (also originally Dolby Stereo ) provide a 4.0 track instead of a 2.0 Stereo?

I don't have a home theater system yet and want to be sure.

I'm guessing they mix them at 4.0 to prevent the front channels playing in the rear channels. Thats not how it sounded in the theater tho

(2020-09-13, 11:16 PM)Onti Wrote: So, will that DTS-HD Master Audio 2.0 Stereo be converted to 4 channels (left, center, right and surround speakers) in a home theater system in the same way as in theaters with a 35 mm print?

If so, why do some blu-ray releases like Platoon (also originally Dolby Stereo ) provide a 4.0 track instead of a 2.0 Stereo?

I don't have a home theater system yet and want to be sure.

In theory, yes. In practice... sort of, and it depends what gear you have. I've talked quite a lot about this myself on here, so it's probably easiest if you take a look around rather than me just repeat the same crap people have heard from me before hahah. The gist is that it'll decode differently depending on your hardware, and in particular which version of the consumer Dolby matrix decoding system your hardware uses: Dolby Surround (original version), Dolby Pro Logic, Dolby Pro Logic II, Dolby Pro Logic IIx, Dolby Pro Logic IIz, Dolby Surround (which is what they rather infuriatingly named the new version), or something completely different like DTS Neural:X. And even then, it might sound different depending on how you configure the hardware. For this reason, I'm currently configuring hardware to do analogue matrix decoding of Dolby Stereo tracks using two different surround processors, but I'm currently frustrated by the hardware I've got to do the actual capture bit so I might hold off on doing it properly until I've got a really nice capture device to use.

The 4.0 tracks I wonder about myself, I've only seen a couple (there's on on Edward Scissorhands, can't remember where else). It might be that they're trying to avoid modern decoders steering stuff incorrectly, or it could be that they're more accurate to the theatre decoders, which may or may not amount to the same thing. Or it could be even less theatrically accurate than a good 2.0 Dolby-matrixed track decoded by "Dolby Surround" (the new version, not the old version)... I dunno.

I've been reading about the subject and I’d like to have something clear for a new preservation I'm thinking about. With, for example, Dolby ProLogic all the DTS-HD 2.0 Stereo tracks are converted into 4-channel audio (Left, Center, Right, Surround)?

Dolby Stereo is not a true 4-channel system, so the DTS-HD 2.0 Stereo will be more adequate than a 4.0 (like Platoon).

(2020-09-17, 02:38 PM)Onti Wrote: I've been reading about the subject and I’d like to have something clear for a new preservation I'm thinking about. With, for example, Dolby ProLogic all the DTS-HD 2.0 Stereo tracks are converted into 4-channel audio (Left, Center, Right, Surround)?

Dolby Stereo is not a true 4-channel system, so the DTS-HD 2.0 Stereo will be more adequate than a 4.0 (like Platoon).

Once again, I'm honestly not sure what you're trying to ask, sorry.

A DTS-HD 2.0 stream can either be encoded as straight up plain stereo (left and right, intended to be played back as just left and right, 2.0) or as content intended to be "decoded" back to more than 2 channels. The Dolby Pro Logic system was indeed designed to decode back to 4 channels, but that doesn't necessarily mean it's what other systems will do. Pro Logic II onwards is different and the DTS versions are also slightly different. If your question was whether you can use Dolby's matrix decoding stuff on DTS streams, then the answer is yes, unless you have a receiver which is funny about letting you do that, which apparently do exist but I've not got one so I couldn't really comment on it.

Yes, 2.0 content that has been matrix encoded from 4 channels down to 2 will indeed *not* sound identical to the 4 original input channels, because the system uses phase shifting to approximate the original 4-channel mix rather than actually recreating it precisely. That said, it may not necessarily be true that an actual 4.0 track is less "correct" (or "adequate" as you put it), because it may simply have been made from a matrixed 4:2 track but stored as 4.0. Conversely, it might have come from the original 4-track master, so would not have the quirks of a 4:2:4 encoded-then-decoded experience. Although Dolby Stereo (or perhaps more correctly, the Dolby MP Matrix) is not a true 4-channel system, the input actually is 4 discrete channels, it's just that the result of playing the matrixed 4:2 track back is not the same as those original 4 channels; it is by definition a "lossy" process (not necessarily in terms of fidelity/resolution but in terms of discrete channel reproduction).

If that doesn't give you what you were looking for you might need to try to rephrase a bit and I'll try my best!

So for old movies recorded in dolby stereo
Are they mixed with 4 discrete channels?
If that's so all the 5.1 "remixes" would be a little closer to the original mix

(2020-09-17, 10:20 PM)ac3 Wrote: So for old movies recorded in dolby stereo
Are they mixed with 4 discrete channels?
If that's so all the 5.1 "remixes"  would be a little closer to the original mix

... How?

First off, if the contents of the actual audio mix are themselves modified then there is no way they are authentic (changed sound effects etc. as often seen in 5.1 remixes).

Secondly, I don't really get what you mean by them being "mixed with 4 discrete channels". Yeah, they'd be mixing a 4-channel master, but that would get matrix-encoded down using the Dolby Motion Picture Matrix system to turn it into 2 channels for distribution on prints etc. The channels, as both I and @Onti have said previously, were Left, Right, Centre (derived from L+R), and Surround (a single channel derived from L+R and phase inverted, though there's a wee bit more to it than that). Obviously this is not the same as 5.1, which is instead Left, Right, Centre, Left Surround, Right Surround, and Low Frequency Effects (the ".1"). This was all done in the analogue realm with equipment like the Dolby SEU4 matrix encoder, and monitored through corresponding analogue equipment like the Dolby SDU4 matrix decoder, in order to check that the decoded 4:2:4 mix still sounded good and reasonably close to the original 4-track input. If not, they'd fiddle with the encoder until they ended up with a 4:2 encoded track that sounded as representative of the discrete 4-channel input as reasonably possible. Incidentally, I have one of these, as do at least two other people on this forum that I know of (wouldn't be surprised if others do too). I'm planning on recording some stuff through two different hardware decoders as soon as I have some other equipment to capture and test them with, which should be very very soon!


I've already tried to explain this as clearly as I thought I could, but I feel like you're missing some part of it so I'll try this again in a slightly different manner. The original 4 channels are turned into 2, but those 2 cannot be turned back into the original 4 in such a way that they sound exactly the same, they are somewhat different but are nonetheless 4 channels of different audio (it isn't just the 2 channels duplicated or whatever). Maybe you need to do some research about the Dolby MP Matrix, same as I did myself not too long ago. The idea is that they were trying to store a 4-channel mix in a way that would fit on the limited space available in the optical soundtrack area at the side of a 35 mm film print; there's not enough space for 4 optical tracks, so they reduced it down from 4 to 2 using a fairly clever matrix encoding algorithm which would allow them to later read those 2 channels and convert them back to 4 again during playback in the theatre. This is known as a number of things depending on context and what you're trying to put the focus on, e.g. Dolby Motion Picture Matrix (the actual matrix encoding system), Dolby Stereo (the theatrical version of the tech), Dolby Surround / Pro Logic (early home video implementations of the same concept), 4:2:4 (referring to turning 4 channels into 2 then back into 4) and so on.

It doesn't exactly help that a lot of the terminology around this particular topic is messy as hell. Dolby now has two completely different products called Dolby Surround, for instance: one is the very first home version of the theatrical Dolby matrix decoding system (most commonly known as Dolby Stereo), and the other is the most recent version of their matrix decoder/upmixer, which came in with the Dolby Atmos generation of home video AV receiver tech. The two are completely different, though! The original Dolby Surround is only capable of turning 4:2 matrixed tracks into 3 channels, at best with a "phantom" centre, possibly because it was cheaper/simpler to use less complex equipment to turn 2 channels into 3 (L/R/S), possibly because people probably didn't really have centre speakers at that point anyway, and possibly a bit of both. By contrast, the latest Dolby Surround is basically more interested with making audio stored as a small number of channels (e.g. 2) sound "good" through many-speaker setups by turning those 2 channels into many more, so if you have 5 main speakers and a subwoofer it'll turn 2 channels into 5.1, if you have another 2 speakers on top of that you'll get 7.1, and so on... point being, this is not an accurate representation of the originally designed 4:2:4 matrixed-then-dematrixed process because obviously L/R/C/S is not the same as L/R/C/Lss/Rss/Lsr/Rsr/LFE or whatever else it's trying to cater for. So... yeah, I get that it's kinda confusing.

If you have specific questions I'll be happy to help, I'm just kinda struggling to get what you guys are asking at the moment and I think it might be because there's some fundamental stuff missing from what you've read/understood thus far and it might help to do some reading on the subject before jumping to any conclusions (such as supposing that 5.1 remixes are faithful to Dolby Stereo because Dolby Stereo is created from 4-track sources).

So, it’s useless ripping audio from Laserdisc. But I was thinking, what happens if I use Dolby Pro Logic with mono (instead of stereo) DTS-HD Master Audio 2.0 and LPCM 2.0 tracks? I suppose that dual mono will be steered to the center speaker in both cases.

Well, I decided to start a new thread about sound:

https://fanrestore.com/thread-3465.html