Film-Tech Forum ARCHIVE: Most common digital format(s) question

This is topic Most common digital format(s) question in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Rick Long (Member # 213) on 12-20-1999, 01:42 AM:

This question is asked of projectionists who are running first-run prints on an almost daily basis.

What percentage of the prints you receive have:

(a) D.T.S., S.R.D., AND S.D.D.S. tracks all on one print?

(b) D.T.S. and S.R.D. on one print?

(d) S.R.D. and S.D.D.S. on one print?

(e) Optical SVA or SR only?

(I am assuming that mono is very rare, nowadays.)

I appreciate the information. Thank you

Posted by Joe Redifer (Member # 3) on 12-20-1999, 04:02 AM:

Most everything I get has SRD. It is very rare if there there isn't any Dolby Digital on there. But most prints are quad format (all 3 digital formats plus SR optical). DTS seems to be on a lot of prints as well, more than SDDS.

Posted by Ken Layton (Member # 133) on 12-20-1999, 09:39 AM:

I remember Men In Black had the first reel with all formats, but every reel afterwards had the Dolby Digital track blacked out!

Posted by Joe Redifer (Member # 3) on 12-20-1999, 05:09 PM:

The best movie ever made in the history of mankind, I Still Know What You Did Last Summer, had reels 2 and 3 in Dolby Digital and SDDS and the rest in SDDS and SR. We just played the entire thing in SR.

Posted by Aaron Mehocic (Member # 15) on 12-20-1999, 05:13 PM:

Almost everything we get has the quad format that Joe spoke of. Last September or October we did get a film with a missing SRD track. It sucked so much, I don't even remember its name.

Posted by Stephen Jones (Member # 16) on 12-20-1999, 07:20 PM:

Most of the prints of late that I come across have all formats somtimes you get one that has only one format or another but thats getting rare these days.As for S.D.D.S there only a very small amount of cinemas here in Australia that use it (THANKFULLY)as the rest use Dolby Digital or D.T.S or both.

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Posted by John Walsh (Member # 168) on 12-20-1999, 08:16 PM:

Most of the films we get are the "the quad format" type; a term I still can't get used to. I keep thing of 4 channel.

On "Air Force One," only the first 2 reels were in SR-D. I would have been nice if there was a note in the can saying that.

Posted by Wallace Logan (Member # 225) on 12-20-1999, 10:03 PM:

I now know why everybody does not have a kind word for SDDS because more often than not
when making prints they miss a few reels
thats frustrating.
Most are all formats I have 3 prints that are
only SRD right now.

Posted by Bruce McGee (Member # 131) on 12-20-1999, 11:48 PM:

Does anybody know off hand what a print from around 1992 with THX in the credits uses for its digital system?

Now, I am going to find a FG thread and talk there.

If you need more info, I can run the last reel again and see if there is anything else on the credits.

Posted by Christopher Seo (Member # 7) on 12-20-1999, 11:54 PM:

I think most of our movies are "quad-track", but some more low-budget fare may dispense with a couple (or in a few cases, all) the digital formats. I noticed MGM seems to be releasing their lower-budget movies with SR and DTS only ("Stigmata", "Flawless").

BTW, what's the difference between SVA and SR? Are there any stereo optical tracks made today which do *not* use some Dolby (or Dolby-clone) process?

Posted by Scott Ribbens (Member # 180) on 12-21-1999, 02:18 AM:

Chris, if I may call you that, I think that Rick may have been reffering to Dolby "A" type noise reduction as some of the older DTS movies had a DTS digital track with a Dolby "A" optical track.

SVA or Stereo Variable Area is the type of sound track that you see on all of the movies that are put out today. Before that there was the Variable Density soundtrack that was mono. Instead of having an area of the soundtrack that is clear, a variable density track was shades of grey over the entire soundtrack area. I'm sure that someone else can do a better job of describing this than I am doing in the sleep state that I am in at the moment.

Most, 99.99% I would think, stereo films that are produced today use some kind of noise reduction. I'm sure if you looked REALLY HARD, you MIGHT find a film out there with a stereo track that has no noise reduction of any kind on it. I saw one once about 4 years ago. Even Woody Allen is using SR, just with no surround. Formats 02, and 03 are the only Dolby formats that use noise reduction, but no surround decoding.

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Scott

Posted by Christopher Seo (Member # 7) on 12-22-1999, 01:47 AM:

Sure, Chris is fine.

Thanks for the information, it clears some issues up. I've just been confused as of late, since I've been working with ancient Kintek processors (I'm used to the CP500...). The Kintek model KT-1005, for example, has sound format options of mono, SVA, and Spec Rec. I know what mono is, and I'm assuming that Spec Rec means that the Kintek can process Dolby SR, but I don't quite know where to place SVA in the scheme of things. Is this feature simply equivalent to Dolby format 02 or 03? Or Dolby A? The Kintek manuals assume that I know what all of these abbreviations mean.

Posted by Scott Ribbens (Member # 180) on 12-22-1999, 03:26 AM:

Chris, not being familiar with that Kintek processor of yours, I looked in the manual downloads section, (very handy, thanks for the work Brad!) and since your model was not in there I looked at the 800 Series manual, in that one they are using SVA to refer to Dolby "A" noise reduction/with surrounds (Format 04). Spec. Rec. Was refering to Spectral Recording (Format 05).

Kintek and some others used to refer to format 04 as SVA, as opposed to mono (01). This is a holdover from before the time of Dolby SR. They could not call it Dolby Stereo because it is not Dolby equipment. I think it was easier to use the "SVA" in the manuals, than to say: "Stereo / A-type noise reduction". On the Strong CPA-10 they had a sound format that was labled SVA. I hope that kind of clears things up.

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Scott

Posted by Scott Norwood (Member # 30) on 12-22-1999, 08:39 AM:

If we wanted to be pedantic about such things, SVA would refer to any stereo-variable-area track (which could have no NR [rare], A-type NR, or SR-type NR). Dolby A and Dolby SR are just noise reduction processes in and of themselves; they are used for some audio-only recording-studio work. "Dolby Stereo SR" is, of course, SVA with SR noise reduction. "Dolby Stereo" usually refers to any type of SVA track with Dolby NR (either A or SR). There's no clear way that I can think of to identify what would be a Dolby Stereo print with type A NR (I've never heard the term "Dolby Stereo A").

Posted by Bill Purdy (Member # 202) on 12-22-1999, 10:55 AM:

Back in 1978-79 there was quite a battle going on between Dolby and mostly Eprad. Eprad has since changed hands and so my comments apply only to the old regime. Eprad maintained that if the film was recorded in "Dolby Stereo" it made no difference whose equipment was used to play it back, and therefore, a theatre could advertise it as being "Dolby Stereo". During that period I was doing a lot of road work for Dolby, but because I was a free-lancer Eprad kept calling me to get me to say that there was no difference, which I, of course would not do. It even got the the point that I was recording those phone calls in order to protect my backside. At any rate, the whole thing went to court and Dolby won and it stands today that you cannot advertise a film as being in "Dolby XXXXX" unless you are reproducing it through genuine Dolby equipment. (This is one of the reasons for some folks buying the CP-45s.)

So, "Stereo Variable Area" (SVA) emerged as the generic term. This became more important when Ultra Stereo developed their own encoder and some low-budget SVA tracks were produced without any involvement from Dolby. As you know, this effort never went very far.

Posted by Ken Layton (Member # 133) on 12-22-1999, 11:07 AM:

Smart also had an advertising ploy----"wide screen stereo" you could say instead of Dolby Stereo. Some theaters would simply say "we have the capability to reproduce film soundtracks recorded in Dolby stereo" without actually saying they were "in Dolby Stereo".

Posted by Tim Reed (Member # 137) on 12-23-1999, 12:05 PM:

Bill, Norm Schneider is in a similar situation today. He's been anti-Dolby for ages.

Only he strutted around, proud as a peacock, when Dolby filed a suit against him for infringing on SR technology. I guess being 'recognized' in this manner provided its own approval, by bestowing the status of 'legitimate contender'!

Posted by Brad Miller (Member # 2) on 12-23-1999, 03:18 PM:

Bill, yet up until everything went "digital", everyone was still advertising "Dolby Stereo" regardless of the sound processor! I see THX falsly advertised this way as well. I always go to the manager and make a nice big argument in the lobby during a rush! If they don't care enough to get their ads right, then I don't care enough to let them do their jobs for a nice stretch of time.

Nowadays the common thing is to advertise "every movie in digital sound", even though in many circumstances this is simply impossible. It's always amazed me how the local 20-something-plex has all SDDS and NOTHING ELSE is suddely capable to play those non-SDDS releases in digital.

Posted by Christopher Seo (Member # 7) on 12-23-1999, 10:04 PM:

Ah, this clears everything up. So the Kintek manual merely used different terms for the equivalent Dolby formats. One more question though... I understand that the idea of stereo variable area tracks is separate from the idea of noise reduction, but what about matrixing? When did the Dolby matrix make its appearance, and what formats was it associated with? Did it always have the 4 channels?

Posted by John Walsh (Member # 168) on 12-24-1999, 01:13 AM:

Dolby SVA came out in about 1975, but it was "Star Wars" (1976) that pushed it to the forefront. At first, you could buy a single (mono) unit called the 364 that had one "A" NR channel. You then fed that to a "E2"; a one channel equalizer. There was no matrix in that product. It was for small, mono theaters.

Then the CP50 came out. The "standard" CP50 only decoded the 3 screen channels. It had two (single channel) Cat.22 NR cards, an "QS" matrix card and three Cat.64 eq cards. Surround decoding was an extra cost option. Later, there was an automation interface to operate it remotely. The sub-woofer option was added later, all for extra cost.

Actually, the concept and equipment to create SVA was developed in (I think) the late 1930's by Western Electric. Being part of the phone company, WE was interested in all kinds of sound-type technology, but didn't seem to pursue the SVA concept and dropped it. So, years later, Dolby bought a few of those old optical sound recorders, and modified them with modern electronics. The WE patents had expired, so Dolby did'nt have to pay any roylties/rights.

So, now Dolby had a noise reduction process ("A"); a device to get two channels of optical sound on film (WE SVA), now they needed to get 4 channels. They wanted 4 channels, because they knew there were still many Cinemascope (4 channel magnetic striped film) installations around. So, they made their complete system as a replacement to the mag tracks, and to match the "3 speakers behind the screen and mono surround) setup. If you had a Cinemascope theater (and there were many of them, not being used) you could rather cheaply get back the 4 channel sound, with out the problems of magnetic striped film (EQ'ing, demagnitizing head, heads wearing out-they only lasted 5-6 features.)

At that time we were in the middle of the 4 channel home stereo "Quadraphonic" era. The idea of this home system was the same, (2 channels matrixed to 4) except the speakers were to be placed in the 4 corners of the room- you sat in the center- unlike the theaters. "Quadraphonic" was only for listening to records. There were video tape recorders, but no one released movies (in fact, then, the studios hated the idea of VCR's, thinking it would lead to piracy) so there was no thought of "Quadraphonic" being used as way to watch films. Several companies made a simlar 2 to 4 decoders for this home market, but Dolby liked Sanyo's "QS" decoder the best and licenced it from them to complete their theater package.

There was a posting at r.a.m.t. where a guy explained very nicely the history of Dolby's use of the old WE optical sound equipment. It might be worth a "Deja-News" look-up. This was about 2-3 months ago.

Posted by Erich Loepke (Member # 166) on 12-24-1999, 01:50 AM:

I'll give a very simplified version of how 4-channel surround works:

You have two sound channels on the film: left and right. Adding left and right gives you the center channel. Subtracting right from left (L-R) gives you the mono surrounds. This only works with sound material encoded in this way. It wouldn't work with a normal CD, for example. The circuitry for doing what I described is very simple and could be built entirely with Radio Shack parts. When someone advertises a "passive surround decoder", it's based on the principle above. This simple solution has problems with signal separation from the different channels, so Dolby added some of its own improvements. This is compatible with two-channel stereo. The center channel information is split evenly between the two stereo speakers, and the surround is out of phase and results in a sound which appears not to come from the center. If you've ever hooked up a stereo receiver at home out of phase, you'll know what I mean. If you were to mix that down to mono, the surround would cancel out and not be heard at all.

Quadraphonic sound of the 70s uses four discrete channels matrixed down to two. One system called CD-4 was developed by JVC and used a record with an ultrasonic carrier that contained the other two channels. The other was called SQ, I believe, and was developed by Motorola and CBS/Columbia Records. This used a complex matrixing scheme involving 90 degree phase shifts. The advantage with this is it was compatible with cheap record players whereas CD-4 required a special stylus and cartridge to play back the ultrasonic portion without wiping it clean off the record.

Posted by Bill Purdy (Member # 202) on 12-24-1999, 05:06 PM:

There is room here for more clarification. first of all, Brad, a lot of people have advertised as showing "Dolby Stereo" when they weren't, and a lot of them have been sternly spoken to by Dolby. I think that by now the matter is too big and too confusing for Dolby to police it properly, but in many communities you will see ads which differentiate between "Dolby" and just "Stereo".

As to how many channels, yes it all started with just Dolby "A" noise reduction for mono tracks, but soon there after the three channel version came out when the Dolby CP-100 was still the only processor. To be sure, the concept went way back, but the problem was the noise level. Dividing the track into two doubled the background noise which was already not too good. By applying Dolby "A" NR the noise level could be reduced enough to allow for the two separate tracks. It seems to me that Ioan Allen (the daddy of the whole project) once told me that the resultant noise is about 1 dB below that of a well made old style mono track. In the meantime, both negative and positive film stocks have improved and when today's SR is added to the mix, we have some pretty damn fine optical tracks.

Back to the CP-100, but the decoder card in the original allowed for only the L,C,and R, which is why most of them eventually sprouted the "SA" (Surround Adapter) series of outboard chassis which housed the early surround cards which were separate from the front channel decoders. I still remember installing the very first hand wired Cat. No. 150 into the Century 21 Theatre in Denver, which must have been sometime in late '78 of '79. (I remember it well because of the truly professional projectionist who could not even run a sound-only reel without full lights down, curtain open. A real showman.)

To expand a bit on the how-it-works description above, after the two tracks (Lt and Rt, for "Left total" and "Right total") are read and been through the appropriate noise reduction, they go into the decoder where the L and the R go straight through almost to the end where they are presented to VCA's, or "Voltage Controlled Amplifiers". At the sametime, through a side channel they are summed and presented to the Center VCA. Also at the same time the two signals go to the steering circuit which analyzes them and if they are alike in both phase and amplitude commands are sent to the VCA's to raise the level for the C channel and reduce the level for the L and R channels. If the Lt and Rt are different, the reverse happens so that they VCA's steer the signals to the L and R channels as a stereo signal. When the steering circuit sees the two incoming signals as the same in level but with one of them leading 90 degrees in phase and the other lagging 90 degrees, these are identified as Surround, passed through a Dolby "B" NR circuit and passed on through the Sur VCA to the amplifiers. Thanks to today's technology they are now able to achieve a whole lot better separation than the 6 dB they started out with. The last I heard, it is now somewhere around 25 dB. No, I don't think that you are going to do this with Radio Shack parts.

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Bill Purdy
Comonent Engineering

Posted by Steve Guttag (Member # 268) on 12-24-1999, 05:29 PM:

Bill is most correct in his description on the events.

In particular, the CP-100 is the original Dolby Stereo processor.

The CP-50 was the "economy" processor designed to be retrofitted into existing 4-track magnetic theatres. It stripped away the "flexibility" the CP-100 had (the CP-100 had 3 format slots so one could "program" it by installing the appropiate format into one of the three slots. The CP-50 on the other hand just did the basics...that it it just handled optical sound formats (magnetic was a pass through since the theatre was expected to already have it's 4-track magnetic system in place).

The first Cat. 150 should have come out around 1978-79 or thereabouts. The CP-200 came out in May of 1980 with the release of EMPIRE and the Cat. 150 was standard for CP-200.

Merry Christmas to all!

Steve

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"Old projectionists never die, they just changeover!"

Posted by Erich Loepke (Member # 166) on 12-25-1999, 09:51 PM:

What I had described in my earlier post was a VERY simplified explanation of how surround sound works. You'd get very little in the way of channel separation with such a setup. It's all the "extras" Bill described that provide for the necessary channel separation and make the system complex. And no, Radio Shack parts wouldn't do for a professional surround decoder when you start talking about steering circuits and Dolby B noise reduction. You have to have the Dolby license to even be able to buy the custom ICs that do these things. I have seen "passive decoders" advertised in audiophile magazines that are based on these simple principles, and do not have the Dolby name associated with them. The drawback with "passive decoders" is they don't do such a good job at channel separation and may not have true Dolby B noise reduction since they are not using the Dolby parts.