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Topic: How Dolby Digital and SDDS Works?

Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999

posted 09-10-2007 09:35 AM

Note, the Dolby logo has ZERO functionality on scanning the Dolby digital track. If they made it functional, it would endager their use of the trademark. Louis is correct, there are four unique corner bits that allow the video aquisition to align itself with the data.

Steve

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Lyle Romer
Phenomenal Film Handler

Posts: 1400
From: Davie, FL, USA
Registered: May 2002

posted 09-10-2007 09:58 AM

quote: Monte L Fullmer
..and the dolby symbol in the middle of the square acts like a center point (target) for the reader.

As Steve said, the Dolby symbol serves absolutely no purpose. The four identical patterns in each corner are the reference points. The only reason the Dolby symbol was there is that they ended up with extra space in the data block pattern and decided to put in the logo instead of a black or white block.

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Sam D. Chavez
Film God

Posts: 2153
From: Martinez, CA USA
Registered: Aug 2003

posted 09-10-2007 10:30 AM

Further on the logo in the middle.

Film wear research before going forward with SR.D showed the center of the area between the sprocket holes has a slight scuff or sanding effect in every test. As such, it was deemed the least reliable place to put fine data so someone decided to put a logo there, kind of a show off kind of thing to do with surplus space. That's all there was to it.

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Monte L Fullmer
Film God

Posts: 8367
From: Nampa, Idaho, USA
Registered: Nov 2004

posted 09-10-2007 02:40 PM

That'll work then-(knew I'd get the right answers when I posted that original comment..which I've only heard from others) ... prob why, when running that WinDRAS program, why that one cel goes green when the corner count is at it's highest...and how it's explained in the WinDRAS program manual of the need for high numbers for corner counts.

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Michael Schaffer
"Where is the
Boardwalk Hotel?"

Posts: 4143
From: Boston, MA
Registered: Apr 2002

posted 09-10-2007 03:43 PM

Has anybody heard from Robbie Hidalgo recently?

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Frank Angel
Film God

Posts: 5305
From: Brooklyn NY USA
Registered: Dec 1999

posted 09-10-2007 05:32 PM

I always wondered how they wound up divvying up what little unused geography existed on the film frame. I mean, I always thought Dolby's approach was quite brilliant -- testing filmstrips for months in real life theatre situations. Did Sony do this, and if they did, how did they wind up choosing the worst area for transport wear? Or were the two of them working without knowledge of each other's digital research and Dolby just beat Sony to the punch and claimed the much better territory?

And can a company "own" a particular area on the film? Suppose the Acme Company invents a holographic sound recording process next year and convinces a few studios to use it, but it needs, let's say, the Dolby area and one of the Sony edges; do either Dolby or Sony get to say, no, those areas belong to us? Someone had to referee the placement of the DTS, SRD and SDDS spaces, no? SMPTE perhaps? And how come Kodak didn't say, sorry boys, that's ours....that's where we put our codes and ID stuff.

Sam, any insight as to how this evolved?

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Louis Bornwasser
Film God

Posts: 4441
From: prospect ky usa
Registered: Mar 2005

posted 09-10-2007 06:55 PM

Dolby was 8-10 years ahead in testing and "staked out" the best area. SDDS tried to use the same area as Dolby; then went for a 100% redesign, in effect modernizing the CDS (defunct) system. Louis

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Sam D. Chavez
Film God

Posts: 2153
From: Martinez, CA USA
Registered: Aug 2003

posted 09-10-2007 11:20 PM

I'd have to disagree that Dolby had that much of a head start (more like a year or two) as a number of the engineers in the middle of the SR.D project were quite fearful of what Sony might come up with, and of course, of their abundant resources. There was also the matter of Sony being one of Dolby's biggest licensing customers at that time.

There were casual talks with Sony to co-op with Dolby on a joint venture but Sony wanted the their name on the box.

Anyway, these were not Sony's top people and as I remember it was a new group formed in the LA area for this project.

One of the little clues to the fact that they did not spend much time looking at either Dolby or DTS conventions is that even the optical preamp d-sub pinout was different from that Dolby and DTS used. No big deal but kind of conceited.

Also the idea of insisting on making all the other processors go upstream and thru the SDDS to get to the power amps.

Basically, they got stuck with the worst part of the film as they started last and thought they could overcome the disadvantage through engineering. I guess they never heard of dirt, scratches or static for that matter.

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Blaine Young
Master Film Handler

Posts: 477
From: Kirkland, WA, USA
Registered: Sep 2006

posted 09-11-2007 12:24 AM

I believe the Dolby Digital patent actually lays claim to the outboard inter-sprocket area. Just as the DTS patent covers the space between the analog soundtrack and the image, and Sony's patent covers both edges outside the sprockets. It would seem that the inboard inter-sprocket area is "free" for future development.

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Steven Gorsky
Expert Film Handler

Posts: 146
From: Frederick, MD, USA
Registered: Sep 2000

posted 09-11-2007 01:58 AM

quote: Mark Gulbrandsen
Sony's present support is nearing zero!

I'm curious now - how has this affected AMC? Having worked for them a few years ago, I remember that they were exclusively using SDDS, but I've been out of the loop for a bit - have they changed their position?

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Frank Angel
Film God

Posts: 5305
From: Brooklyn NY USA
Registered: Dec 1999

posted 09-11-2007 03:03 AM

I would really be surprised if any of them can patent the area on the film as belonging to them. If anything, Kodak was using that space since the big bang. No doubt the patents indicate where they put their unique digital image, or code in the case of DTS, but the area itself, I doubt it is patentable as it's existed for a century, I wouldn't think.

Like in my example, if some other company came up with a system totally different than any of the three but wants to use those areas and this company convinces a couple of the studios and a few of the chains that this system is so much better than the existing systems -- like it can carry 12 channels like DCinema or whatever, and the studios and the chains agree they go ahead and make these prints, can either Dolby or Sony now say no one else can now do whatever they want on undeveloped film? Seems a stretch. Then that's just me.....I have an instinctual aversion to corporations wanting to own the world. Like "Just do it." How can that BELONG to a company? People have been saying that long before those snotty execs were even a gleam in their daddy's eye.

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Michael Schaffer
"Where is the
Boardwalk Hotel?"

Posts: 4143
From: Boston, MA
Registered: Apr 2002

posted 09-11-2007 03:28 AM

quote:
Note, the Dolby logo has ZERO functionality on scanning the Dolby digital track. If they made it functional, it would endanger their use of the trademark.

Why?

quote: Sam D. Chavez
Also the idea of insisting on making all the other processors go upstream and thru the SDDS to get to the power amps.

That was a necessity simply because of the 8 channels which would have been difficult to feed through conventional 6-channel processors. Plus they wanted to have their own EQing and all that. Which I know a lot of people found "too harsh", but however good or bad that was, it made sense as a concept. Plus it was the first cinema processor which actually had balanced outputs (or was it?).
And, of course, we all loved the idea of bringing 5 front channels back, didn't we?

quote: Sam D. Chavez

Basically, they got stuck with the worst part of the film as they started last and thought they could overcome the disadvantage through engineering. I guess they never heard of dirt, scratches or static for that matter.

I know we have been over this many times here in these pages, and it doesn't really matter anymore since Sony, whatever they say about whatever support is allegedly still existing, effectively dropped the format, so it is really only a historical footnote now.

But I have to say we had a lot of SDDS in theaters I worked for in Germany, and we had very little problems with the format, plus it was the only one that people could reliably pick out as sounding "better" than the other ones (and yes, we had a number of auditoriums in which all 3 were installed, so direct comparisons were possible).

That may have had something to do with that we had mostly Kinoton projectors which are nicer to the film (including and particularly the edges) because of the smooth Delrin runners. Plus the handling and cleanliness standards in these booths were generally higher than most of what I have seen on these shores. So that may all have played into that, I guess.

On the other hand, I have also seen a few prints which were totally trashed but on which the SDDS track still worked stably.

SDDS claimed that superficial dirt and scratches shouldn't matter too much since the track was (actually, is) in the cyan layer and the camera was optimized for just the wavelength produced by the red LED illumination going through the layer, so it should not "see" too much of these scratches.

One could argue that all that doesn't matter since a technology has to be "rugged" enough to "survive" all the abuse and bad handling and being run on badly aligned and maintained projectors the films take these days in 16-plex booths operated by undertrained and undermotivated kids.

But that would mean accepting the "lowest common denominator" and "as long as it still somehow runs, there is no reason to fix or improve it" standards which are all too common today. That wouldn't appear to me to make sense, especially not in this context in which people still argue for the return of 70mm...

Another problem was that a lot of "technicians" simply did not understand how the equipment worked and was supposed to be aligned. I have come across processors more than once which had obviously been set up with the fader set to 6.9dB or 7.2dB... In fact, I remember bumping into "technicians" which complained about the processor not having a "7.0" setting...

[Roll Eyes]

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999

posted 09-11-2007 06:49 AM

Michael...it is merely one of the rules of a registered trademark that it be "non-functional." Functional things are patentable, I guess. I'm getting this from a patent and trademark attorney.

As to patenting an area of the film...no...but the method of encoding the digital audio on a place of the film, yes. That is, you could claim an area of the film for the purpose of encoding bits as square blocks for the purposes of encoding audio or data and the method of recovering that information. For instance, DTS' dashes don't resemble Dolby's square blocks at all so regardless of where they put those dashes, there wouldn't be any enforcable patent infringement by either party. SDDS and Dolby are the most similar in that they have "bits" of data encoded on the film but their method of recoverey is different with SDDS strobing the film while Dolby used the perforations to separate the bits and there are no doubt many other difference in how the digital data is encoded. Note, Kodak went to magenta edge coding to avoid interference with SDDS' track. Kodak would want film the be as accessible to as many people as possible...it sells more film that way.

As to Sony's choice to not conform to the established 0-10 scale on the volume control...that was THEIR stupidity and probably arrogance. There simply was no need to try to force/establish a 0.0dB reference in the cinema exhibition industry. That train had left the station long ago.

Note too, the 2000 series only had a +/-10dB range...as many people set their volume below reference...by continuing to target the magic number "7"...one would effectively have a +3/-17dB range on a 2000 series system which would work...if they don't internally clip the signal. Sony at least made it a +10/-30dB range on the 2500 and 3000 series systems.

Steve

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Bastiaan Fleerkate
Film Handler

Posts: 85
From: Linschoten, Utrecht, The Netherlands
Registered: Jun 2006

posted 09-11-2007 08:50 AM

quote: Frank Angel
And can a company "own" a particular area on the film? Suppose the Acme Company invents a holographic sound recording process next year and convinces a few studios to use it, but it needs, let's say, the Dolby area and one of the Sony edges; do either Dolby or Sony get to say, no, those areas belong to us? Someone had to referee the placement of the DTS, SRD and SDDS spaces, no? SMPTE perhaps? And how come Kodak didn't say, sorry boys, that's ours....that's where we put our codes and ID stuff.

If I'm correct, on the other side of the film (were there is no SR-D track between the perforations). Is an empty place for another SR-D-like soundtrack...
Why is this space not used for alternative soundtracks? Is it because of the patents of Dolby, that nobody can have their soundtrack between the sprocket holes?

I also think DTS could upgrade their soundsystem to play 12-track DVD-discs... the timecode is already there. Or another company could make use of the timecode to play multi-track sound with a file you can download from the internet...

The only thing is... if you have 12-track sound. The post-production would have to make 12-track effects. It's more cost-effective to make 6-track sound. It uses less data and is quicker to mix...

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Mark Gulbrandsen
Resident Trollmaster

Posts: 16657
From: Music City
Registered: Jun 99

posted 09-11-2007 09:20 AM

quote: Michael Schaffer
Has anybody heard from Robbie Hidalgo recently?

First I heard from Carl that he was working for Shure Brothers but then I heard from pretty reliable sources he kicked the bucket as a result of his heart attack. Who do you believe? We sent him a 3000 penthouse for repair over two years ago... never saw it again.

Mark

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