Talk:Dolby Stereo

Matrixing vs. Noise Reduction

This article is confusing because it conflates the matrixing algorithm with the noise reduction. In the context of 35mm film, "Dolby Stereo" generally means "Dolby A"-type noise reduction, and that almost always meant it had 4 channels of sound encoded as 2.

I don't think it is correct to suggest that the dematrixing be called "Dolby Stereo," which this article implies. It's a bit problematic to call the dematrixing Dolby Pro-Logic, because that name did not exist at the time and is not generally used in the cinema industry, though it is probably the best name that fits.

If you look at a Dolby A -encoded film print, it will just say "Dolby Stereo" (if the soundtrack format is labelled at all!) and you have to know that means A-type noise reduction, and thus set your cinema processor for "Dolby format 04: Dolby Stereo A-type," which applies the Dolby A noise reduction decoder as well as the Dolby Pro-logic dematrixing. Jhawkinson 08:58, 25 February 2007 (UTC)

Well, that's because the term "Dolby Stereo" itself conflates both. I don't really see much basis in your complaint. The article puts the emphasis on the matrixing, but that seems fair to me, as there's already a separate article for Dolby A NR itself.

As far as I'm aware, Dolby use the term "Dolby Surround" for the matrixing system alone, out of the context of actual film prints. Presumably that could be mentioned. Hmm, I see there's already a separate article for Dolby Surround. That's not too good. The articles should almost certainly be merged. --KJBracey 15:12, 25 February 2007 (UTC)

Dolby MP, Dolby Stereo, Dolby Surround, Pro Logic, and Dolby Digital are all surround sound systems. Dolby A and Dolby SR are both single channel noise reduction systems. A single channel noise reduction system cannot displace a surround sound system. This is because they do different things. Yes, the Dolby surround sound systems incorporated Dolby noise reduction, but they are still different beasts.

Here are some quotes from Dolby documents:

[1]Dolby Stereo
Dolby Stereo technology provided such a highly practical 35 mm stereo optical release print format that by the late 1980s almost all major titles were being released with wide-range multichannel stereo soundtracks. In the space allotted to the conventional mono optical soundtrack are two soundtracks that not only carry left and right information for stereo sound, but are also encoded with a third center-screen channel and most notably a fourth surround channel for ambient sound and special effects.
Dolby SR
Dolby SR is an advanced recording process applied to Dolby Stereo soundtracks, greatly improving their dynamic range (the ratio of the loudest sounds to the softest). Introduced in 1986, Dolby SR (spectral recording) provided more than twice the noise reduction of Dolby A-type, and, moreover, permitted loud sounds with wider frequency response and lower distortion. The 35 mm optical soundtracks treated with Dolby SR not only sounded superb in cinemas equipped with new Dolby SR processors, but also played back satisfactorily in all cinemas. As a result, today, the analog soundtracks on virtually all prints are Dolby SR tracks.

[2]Dolby Stereo, the company's original film audio format and predecessor to Dolby Digital, is still providing improved surround effects in many venues.

[3]Dolby Spectral Recording (SR)
Dolby's next advancement in analog film sound. This technology delivered a significantly improved dynamic range over Dolby Stereo and is still included today on nearly all 35 mm film prints. On films with digital soundtracks, the SR track is used in cinemas not equipped for digital playback, and it serves as a backup in case of problems with the digital track.

I believe your confusion arises because Dolby Stereo originally referred to a technique of encoding stereo sound onto optical film stock. It therefore exhibited a particular signal to noise ratio which was subsequently improved by deploying Dolby SR. For this reason Dolby Stereo and Dolby SR are sometimes referred to together. However, Dolby Stereo cannot be displaced by Dolby SR because the former became a surround sound system and the latter was always a single channel noise reduction system.

Hope this helps. Martin.leese 21:59, 26 March 2007 (UTC)

Don't agree with your last edit. Dolby Digital didn't displace Dolby Stereo, Dolby SR did - ie the same system but with SR noise reduction instead of A. Note that Dolby use "Dolby SR" both to refer to the noise reduction itself, as well as the Dolby Stereo system with SR noise reduction. Dolby Digital certainly is the next generation format, but it hasn't displaced Dolby SR, at most it coexists. But when did Dolby SR enter use on film prints? The Dolby SR article says 1990s, this article used to say 80s. —The preceding unsigned comment was added by KJBracey (talk • contribs) 23:20, 26 March 2007 (UTC).

I must object to this. Where are your references for these claims? I quoted three Dolby documents. Please give some verification for your claims or undo your damage. Martin.leese 23:38, 26 March 2007 (UTC)

Assuming you mean the naming, then the very documents you quoted above do it, all the way through. They refer to the current analogue (=Matrixing+SR) sound system as just "Dolby SR", as opposed to the original "Dolby Stereo" (=Matrixing+A) system. Yes, I agree that's muddle-headed, maybe they should have gone with "Dolby Stereo SR", but who are we to argue with Dolby?

As to displacement, again the documents explain that. Dolby SR is present on every Dolby Digital print. Dolby SR (matrixing+SR) displaced Dolby Stereo (matrixing+A) - ie Dolby Stereo is no longer used. But Dolby Digital did not displace Dolby SR; Dolby SR is present on every Dolby Digital print for back-up and compatibility, and Dolby SR is used on its own on some lower-budget films. KJBracey 00:10, 27 March 2007 (UTC)

Ah, here's a better example of them using Dolby SR to refer to the entire analogue film soundtrack system, even down to the number of channels [4]. See top half of page 3. "A Dolby SR soundtrack features four channels with left, centre, and right speakers behind the screen, and a single surround channel used for ambiences, atmospheres, and special effects." --KJBracey 00:18, 27 March 2007 (UTC)

KJBracey is correct here. As a practitioner of the field of motion picture projection, I can speak from personal experience. But we can back things up with harder data, too. First of all, you contend that noise reduction and surround systems are different. That is true, but in the film context, the terms "Dolby Stereo" and "Dolby SR" imply both a particular noise reduction system (A and SR, respectively), and also a particular dematrixing algorithm (Dolby Pro Logic, though it is not called that); this is confusing, which is why I started the "Matrixing vs. Noise Reduction" topic here on the Talk page. The article needs to be fixed.

Anyhow, the edit we're questioning is when you changed "Dolby Stereo was displaced ...by Dolby SR" to "Dolby Stereo was displaced...by Dolby Digital." This change does not reduce any confusion between noise reduction and matrixing, as your edit summary claims. Furthermore, you claimed it reduced confusion but you actually changed the facts. If you were to have claimed "The noise reduction used changed from Dolby A to Dolby SR," that would be correct, but I don't think is quite in context here (because this is an article on Dolby Stereo, and hence Dolby A).

Your quotations do not support the contention that Dolby Stereo was displaced by Dolby Digital, not by Dolby SR. So there's nothing to refute in them. In your text above, you say, "However, Dolby Stereo cannot be displaced by Dolby SR because the former became a surround sound system and the latter was always a single channel noise reduction system." This is not correct. You may find it instructive to consult the "Dolby CP45 Cinema Processor: Users' Manual" [5], Appendix D, "ABOUT DOLBY FILM SOUND FORMATS" (page 39 of the PDF) (the CP65 manual might be more strictly correct, but Film-Tech's copy is missing a few pages and has ordering problems, and they have the same text):

1. How Dolby Noise Reduction Works

...
The CP45 has two channels of Dolby A-type noise reduction and Dolby SR circuitry to decode the two soundtracks on Dolby Stereo release prints (the left, center, right, and surround channels are derived from the two soundtracks after the Dolby noise reduction decoding).

2. About Dolby SR

The soundtracks on Dolby Stereo SR prints have been encoded with the DolbySR (spectral recording) process, rather than Dolby A-type. DolbySR also boosts quiet sounds when a recording is played and brings them back down again when it is played back.
...

Is there any remaining ambiguity you need resolved? jhawkinson 00:58, 27 March 2007 (UTC)

Cheers, jhawkinson. To summarise the terminology:

• Matrixed+A content: Dolby Stereo (optical soundtrack on 35mm film prints)
• Matrixed+SR content: Dolby SR (optical soundtrack on 35mm film prints)
• Matrixed content: Dolby Surround (outside cinema context, eg TV, DVD)
• Dematrixing systems: Dolby Surround / Dolby Pro Logic / Dolby Pro Logic II / Dolby Pro Logic IIx (all outside cinema - cinema dematrixing system has no marketing name, but is basically equivalent to the consumer Dolby Pro Logic; the original "Dolby Surround" decoders were cheap passive decoders designed to get some result out of a Dolby Surround soundtrack - the name Pro Logic had to be invented to describe the proper, active decoder when a consumer version became available)

I note that Dolby now talk about Dolby Pro Logic II encoders, which I've seen mentioned for live encoding with games - presumably these have 5-channel inputs with matrices set up for optimum Pro Logic II decoding.

Also, there's Dolby Stereo 70mm Six Track, but that's a totally separate 6-channel magnetic system on 70mm prints. That too has changed from using A noise reduction to SR, but with no associated name change. That naming dates from the days when everything they did was "Dolby Stereo XXX" - they did once use the names "Dolby Stereo SR" and "Dolby Stereo Digital".

Now, this sort of information really needs to be in the article, and again that goes back to merging Dolby Stereo and Dolby Surround. Dolby SR has its own article, but that's also a little wrong - it talks almost solely about noise reduction, but then there is a whole separate Dolby noise reduction system for that...

I'd suggest having one "Dolby Surround" article about matrixing covering all of Dolby Surround, Dolby Stereo and Dolby SR, with appropriate links to the noise reduction page. Titling the page would be awkward though, as Dolby don't really have a name for the matrixing itself; "Dolby Surround" is closest, but in Dolby's usage that pretty much implies a non-cinema context... --KJBracey 08:16, 27 March 2007 (UTC)

(I was addressing Martin.lees when I asked about ambiguity...in our side discussion of whether SRD displaced A...; but anyhow...) One possibility is to use the term "Dolby Stereo SR" to talk about SR and matrixing. This is possibly a bad idea since the term is basically unused (but does appear in some Dolby literature). I don't know if this is a good idea or not.

Don't you think that "Dolby Pro-Logic" is really the right name for the matrixing? Another problem is that this needs to integrate with Dolby noise reduction system (which redirects from Dolby A, but doesn't mention dematrixing). Maybe we need "Dolby Surround (cinema)"? I'm not sure how to solve this problem, but Be Bold :) jhawkinson 08:38, 27 March 2007 (UTC)

Dolby keeps changing terminology over time. They only ever used to use "Pro Logic" for the 2nd-gen (and later) decoders, and even then the logo said "Dolby Surround Pro Logic". As far as I can see, "Dolby Surround" was the label they stuck on matrixed TV programmes. They used to be very consistent about Dolby Surround being the content, and Pro Logic specifically referring to the advanced decoder. But with the advent of 5-channel Pro Logic II (whose logo drops the "Surround"), they started talking about Pro Logic II encoders. But anyway, I don't think Pro Logic is a good name to use for the basic matrixing system itself. But I note that there's a Dolby Pro Logic page too. Another merge candidate. --KJBracey 09:24, 27 March 2007 (UTC)

So, the pickle we're in is that there is no historically accurate term. So we can 1) Fudge a term in use at the time ("Dolby Surround" and variants) 2) Use the term that makes sense now ("Pro-Logic"), 3) choose a generic term ("Cinema sound dematrixing"). I think I'd favor 2 or 3 over 1, but I don't think either of is quibbling about the name...Another problem page is Surround sound. Maybe we could just assert it doesn't cover cinema sound and not worry about it? Bleh... jhawkinson 13:53, 27 March 2007 (UTC)

You can pick your way through Dolby's sites and not be left much the wiser. It's not that any of the technologies have been renamed as such, it's just that each incremental improvement, or consumer version of the same, gets a new name, even if it incorporates a lot of the previous system. Then the corollary is that the old name implies the absence of the new improvement. But they're very bad at naming the underlying components.

I really don't like "Dolby Pro Logic" to describe the technology though. Dolby have never used this naming to refer to encoders or to label content, that I'm aware of. All LCRS-encoded material is Dolby Surround/Stereo/SR, and when pressed to talk about the encoding, they refer to 2-channel content as "Dolby Surround encoded". "Pro Logic" on its own refers specifically to decoders.

However, they have used "Dolby Pro Logic II" to refer to content, encoding and decoding; there's even a "Dolby Pro Logic II" 4-second trailer available. So "Dolby Pro Logic II" is the name which covers the latest version of the entire technology, but it hasn't totally displaced "Dolby Surround". But it feels a little specific for a general article. Ah, and of course "Dolby Pro Logic IIx" is back to just being decoders again. --KJBracey 16:29, 27 March 2007 (UTC)

Ah...semantics. You folks do know that Pro Logic is a term used on the CP500, right? Of course that long post-dates "Dolby Stereo" (meaning A type) but I thought I'd mention it.Filmteknik (talk) 14:42, 18 April 2010 (UTC)

Dolby SR

I changed the date for SR to the 1990's not 1980's. (I didn't notice I wasn't logged in so that was me.) SR noise reduction came in in the early 1990's and it was dual inventory; separate prints for Dolby Stereo SR (Dolby SR for short) and Dolby Stereo (meaning A-type). SR became the standard around the mid 1990's.Filmteknik (talk) 14:42, 18 April 2010 (UTC)

Wiki Education assignment: Reading Culture

This article was the subject of a Wiki Education Foundation-supported course assignment, between 18 January 2022 and 11 May 2022. Further details are available on the course page. Student editor(s): Juuyuau (article contribs). I added a citation to the part that requires a reliable source about the cost of CinemaScope and edited the part on the coworking history of Uhlig with Dolby. Also, a marketing strategy on Dolby Stereo. That's all I got from my readings about the history of Dolby Stereo :^). — Preceding unsigned comment added by Juuyuau (talk • contribs) 00:10, 17 April 2022 (UTC)

@Juuyuau: You are a scholar and a titan in your field, my friend. Well done. I cleaned up some. Technically, the lead section does not have citations, but rather is a standalone summary of the body which is already fully written and cited WP:LEADCITE. But I'm not familiar with the sources, and that stuff is pretty darn technical ;). — Smuckola(talk) 01:02, 17 April 2022 (UTC)