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Topic: Help! no sound from cyan track with Kelmar IR reverse scan
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Scott Norwood
Film God
Posts: 8146
From: Boston, MA. USA (1774.21 miles northeast of Dallas)
Registered: Jun 99
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posted 05-29-2005 10:16 AM
The problem with digital is the failure mode. Few theatres have optical systems which are perfectly aligned, but the system fails gracefully and the result is acceptable unless the alignment is way off (i.e. excessive dialogue audible in the surround channel, etc.). Further, even without test films and equipment, pretty much anyone can get an optical system to reproduce sound, even if the alignment isn't perfect. By contrast, digital either works or it doesn't, and it is difficult or impossible to tell why it isn't working without test equipment.
I still say that any print with an unplayable soundtrack is defective and should be reported to the distributor as such. Unless it is a single-inventory release (which hasn't been done yet for a major title, as far as I know), he should get a silver-track replacement. If no one complains, film distributors will assume that there are no problems.
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John Hawkinson
Film God
Posts: 2273
From: Cambridge, MA, USA
Registered: Feb 2002
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posted 05-29-2005 11:24 AM
The real reason that the digital sound we have today is not as reliable as analog sound is because it was not engineered for that level of reliability--it was engineered to do more (5.1 discrete) than the analog soundtrack, but in less physical space.
So, because SRD is in much less area than the analog track, and in a location that is easier to damage, it is not as robust. If it were blown up larger and took up more area, the SNR would be that much better and damage would be tougher.
SDDS seems to have its own special sets of problems (is it printing? Is it wear on the edges? Is it dirt migration?).
I guess you should be able to argue that DTS ought to be capable of matching the reliability of the analog track, at least where the discs are undamaged and present. I don't really have a good explanation for why that doesn't seem to be the case [ok, ok, moving parts?].
All in all, though, I don't think the wrong engineering choices were made. It's simply the case that rock-solid robustness was not a design goal for SRD and SDDS. One vaguely wonders how reliable a modern-day CDS reader might be ![[Smile]](smile.gif)
--jhawk
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Frank Angel
Film God
Posts: 5305
From: Brooklyn NY USA
Registered: Dec 1999
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posted 05-30-2005 02:16 AM
quote: Steve Guttag
Digital audio is working rather well for DVDs and a slew of broadcast equipment. AES/EBU is pretty darn reliable.
It is, for the most part, Steve, but in the recording studio right upstairs from me one of the top engineers in the country has a saying....In digital, if you don't have it down three times, you don't have it at all. He always has multiple machines runnning on ever session.
And John raises a really good point....how much better than any of the current digital on film systems would the original Kodak CDS system be in terms of reliability, given that it had the entire space of the analog track. It wasn't using left-over geography -- it had plenty of uninterrupted space. Reliability might have been quite as high as analog. Anyone ever work with that system in a regular theatre situation? In theory it had to be as reliable as analog because there was no backup whatsoever. I wonder if it was, especially over splices & the like.
I think Dolby really did their homework in R&D on where to put their track. They went to something like 30 regular theatres and gave them 20 feet of black film and had it spliced into their trailer pack. They had the theatres run it for 3 months and then they took them back and inspected them for wear. They compiled the data and discovered that the least wear was exactly where they decided to put the track. In fact, they were toying with the place they first were looking at, i.e., the film edges (ala SDDS) as it seemed like a natural place to consider. But the wear patterns told them this area was very problematic. Sony attempted to compensate for the wear problems in this area by redundency on the each side, but from what we keep hearing, when prints get older, even doubling the tracks doesn't seem to be enough.
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