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Topic: How Dolby Digital and SDDS Works?

Louis Bornwasser
Film God

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

posted 09-11-2007 10:21 AM

Bastiaan: One of the problems with audio is that the optical recorder/printer favors one side. In other words, the side with the soundtrack. Note that both dts& Dolby are physically close to the analog track and can be easily processed at the same time. The SDDS recorder is a "penthouse-like" arrangement on top of a normal Westrex camera, which does dts/analog/Dolby Digital internally. Louis

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John Walsh
Film God

Posts: 2490
From: Connecticut, USA, Earth, Milky Way
Registered: Oct 1999

posted 09-11-2007 11:03 AM

I don't think you could 'patent' an area on the film. If I could talk studios into using CDS again, placing it along the edges, who could legally stop it?

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Blaine Young
Master Film Handler

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

posted 09-11-2007 01:55 PM

I'm certainly not a patent attorney, but if someone tried to place a new digital audio track in between the sprocket holes on the same space that Dolby is using, I'm fairly confident that Dolby would have something to say about that.

There are other patents which cover digital storage of other information in between the sprockets or between the film edge and the sprockets, which have nothing to do with Digital Audio storage or playback which (I would think) wouldn't infringe on patents by Dolby or Sony.

All of the patents for the various digital audio systems clearly outline where their data is place upon the 35mm film. And the CDS system clearly outlines their data is placed between the image and sprockets on either the left or right of the image (clearly indicating a 70mm application). Having CDS tracks placed elsewhere on the film isn't covered by their patent (which is due to expire before too much longer anyway), and I suspect they'd have to start over.

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Louis Bornwasser
Film God

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

posted 09-11-2007 02:49 PM

I'm sure the patent specifies where. I'm also sure that the print company will put any track where the film company says. In Dolby's case, there are just too many cinemas equipped to make a change. Same for analog. Louis

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Stephen Furley
Film God

Posts: 3059
From: Coulsdon, Croydon, England
Registered: May 2002

posted 09-11-2007 03:52 PM

quote: Blaine Young
I'm certainly not a patent attorney, but if someone tried to place a new digital audio track in between the sprocket holes on the same space that Dolby is using, I'm fairly confident that Dolby would have something to say about that.

Possibly; I believe that the Dolby patent actually covers the use of the space between the perforations on both edges, in case they ever wanted to use it for some future extension of the system. I doubt they could stop you using it for something quite different however. If I was to buy a roll of print stock, surely nobody could stop me from printing a green triangle between each perforation if I wanted to, could they? What if somebody had proposed an alternative use for this space, at the time that Dolby Digital was being developed, encoding the text for fifty different languages worth of subtitles for example, or even nothing to do with the film, like storing interesting photographs of barbed wire that the projectionist could look at in his spare time if he got bored? No doubt Dolby would want to stop this, as it would be incompatible with their sound format, but could they actually stop it, short of buying up the company promoting the alternative use, and killing it off.

As for what would happen to any system which tried to use this area for some other purpose today, now that Dolby Digital has become so widely used, I would suggest exactly the same as happened to CDS when they tried to take over the analogue track area on 35mm prints.

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Benjamin John Doman
Film Handler

Posts: 35
From: Slough, Berkshire, England
Registered: Jun 2007

posted 09-12-2007 02:19 PM

Hi All,
We have a 6 screen theatre in Malta with SDDS throughout (plus SR-D in one). Someone told them that SDDS was the future when the place was built! They are having big issues with the physical quality of the SDDS track. They have had support direct from Sony for there units. Had a client in the UK recently who picked up a 3000 unit on e-bay for a couple of hundred pounds. It packed up after two weeks! Always thought SDDS sounded the best of the lot, but they never made any effort to be compatible with anyone else. There are very few cinemas in the UK with it fitted.

Incidentally, some prints started coming through with a CYAN coloured Dolby Digital track (as well as the cyan analogue track) recently. Had a lot of complaints that the track was wearing off of the print after the first dozen or so shows. Has any one had this problem in the States or is it just a UK thing?
Regards, Ben

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Blaine Young
Master Film Handler

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

posted 09-12-2007 10:44 PM

I don't recall having seen a cyan SRD track. I have seen sections of SDDS tracks peel off when removing splicing tape.

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John Hawkinson
Film God

Posts: 2273
From: Cambridge, MA, USA
Registered: Feb 2002

posted 09-12-2007 11:00 PM

Anything Else, the first domestic US cyan release, printed by Technicolor lab in Rome, had a cyan dye SRD track. Apparently this was not the way it was supposed to have been, and every subsequent US release I'm aware of fixed it.

But it seems like something that could happen if a lab were confused. So please make sure they find out and fix it!

--jhawk

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Tim Reed
Better Projection Pays

Posts: 5246
From: Northampton, PA
Registered: Sep 1999

posted 09-12-2007 11:39 PM

quote: Bastiaan Fleerkate
Is it because of the patents of Dolby, that nobody can have their soundtrack between the sprocket holes?

We've had this discussion before. No one can actually lay claim to the film "real estate," it's either recommended practice or convention.

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Tim Asten
Film Handler

Posts: 98
From: Brighton, United Kingdom
Registered: Nov 2006

posted 09-13-2007 06:35 AM

Talking of digital soundtracks, I'm sure I heard of a system that used transparent digital information actually recorded on the picture emulsion which was read by an ultra-violet reader and would therefore mean that the soundtrack would be invisible on screen. I don't know whether this system worked or even existed. Tim.

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Richard Fowler
Film God

Posts: 2392
From: Ft. Lauderdale, FL, USA
Registered: Jun 2001

posted 09-13-2007 11:53 AM

The UltraViolet coating was a Kodak project which was talked about for sound and data information; I remember this being discussed during the late 1980's at some SMPTE meetings. The early 1990's barcode based Kodak KeyCode for data and Dolby and others took care of the sound issues [Wink]

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Bernie Anderson Jr
Master Film Handler

Posts: 435
From: Woodbridge, New Jersey
Registered: Apr 2000

posted 09-13-2007 03:24 PM

From my understanding, the DD logo in the film is there as a source of pride. Correct me if I'm wrong, but the square is made up of a grid, 67 by 67 blocks. When the process was being developed, alot of engineers, said that it would be impossible to scan that small of an area at such a rate of speed with that much accuracy. Dolby not only got the block to scan, but the Dolby Techs threw in the DD logo to thumb their noses at the naysayers. That's the folklore that I heard. Don't know how true it is. But I've heard that story twice now.

Bernie

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Michael Schaffer
"Where is the
Boardwalk Hotel?"

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

posted 09-13-2007 09:17 PM

It's 76x76, not 67x67 "fixels" per block. And the story behind the logo has been addressed in this very thread by people who have the actual inside knowledge (e.g. Sam), just a few posts ago. You know, Bernie, it sometimes makes sense to actually read the discussion before "contributing"...

quote: Steve Guttag
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.

Thanks for clarifying that!

quote: Steve Guttag
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.

That's true, I had almost forgotten about the -10dB limit. I have seen the clipping lights on the units come on many, many times, obviously the result of overEQing with a lot of boosting rather than cutting. That, plus installers wanting to match the standard X curve at all costs even in very large auditoriums (and the SDDS systems were, at least initially, perceived as a "high end bonus system" and so typically found in the larger auditoriums) plus the PN deficiency noted by you led to sometimes extremely harsh sound which even -10dB did not take care of in the eyes (ears) of operators and audience...

quote: Louis Bornwasser
The SDDS recorder is a "penthouse-like" arrangement on top of a normal Westrex camera, which does dts/analog/Dolby Digital internally.

And one of the biggest problems I have seen time and time again with SDDS tracks is that they were not correctly printed, meaning, centered on the film. I don't recall what the typical offset was, but I think they were often "pushed over" too far in the direction of the picture side, sometimes so much so that the P side edge marking was unuseable - resulting in total mistracking of the P side and constant DCMs (Digital Concealment Mode), falling back to the backup info on the other side.

The DCM actually worked pretty well in general, but a problem was that even with 6-channel titles, the processor would put the backup mono sum of the dropped out channels from the other side on *all* channels on the affected side, including the LE or RE channels, so that resulted in a weird "pumping" effect as that channel only came on when DCMs occurred. The only solution for that was to switch the system to 6-channel output (provided all 8 were actually installed, which wasn't even the case in all screens in the Sony Center in Berlin...) whenever you had a 6-channel release (in other words, most of the time), or simply switch those amps off.

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Mark Gulbrandsen
Resident Trollmaster

Posts: 16657
From: Music City
Registered: Jun 99

posted 09-14-2007 11:12 AM

FWIW: Sony also had to license many of Dolby's patent's to be able to place and scan the digital track onto and back off the film. Bobby Pinktson once told me that Dolby had patented many aspects of that stuff a number of years before SRD was ever generally made avaialble and that is why Sony first demoed SDDS off a hard drive at Showest. This may also be that part of why Sony wants to see SDDS go bye bye... renew and keep paying those hefty license fees to Dolby. Kinda like RCA paying Farnsworth the patent royalties....

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Louis Bornwasser
Film God

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

posted 09-14-2007 12:52 PM

I once had a conversation with a former Dolby employee where we determined that Dolby made more money from SDDS per unit sold than they did on their own processorsz. Louis

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