Film-Tech Forum ARCHIVE: Splices on CDS Film

This is topic Splices on CDS Film in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Max Biela (Member # 1919) on 10-19-2003, 01:50 AM:

Hi everyone!

Speaking of SRD dropping out in the 8 perf / 2 perf splicer topic: What about CDS? I've downloaded the manual but I've found nothing on splicing CDS Film. How much data must be covered by the tape to make CDS cut out?

Max

Posted by John Pytlak (Member # 331) on 10-20-2003, 09:20 AM:

The paper "Cinema Digital Sound -- Systems Overview", presented by Kodak's Ronald Uhlig and ORC's Howard Flemming at the 1990 SMPTE Conference in NYC said:

quote:
The CDS system has been designed to be able to play sound with no loss in quality even with a bit error rate as high as 10^-2, or in other words, with one bit in every 100 incorrect....Even if there are occasional bursts of errors over that rate, such as might occur at a splice, an efficient concealment mechanism renders them almost always inaudible.

Details of the system were provided in the paper "Cinema Digital Sound -- The Technology", presented and demonstrated at the same SMPTE technical conference.

Posted by Frank Angel (Member # 248) on 10-20-2003, 11:14 PM:

I seem to recall (and I'll admit, recall these days isn't my best function) that CDS had the ability to replay x number of microseconds of the last readable audio and splice it in so as to cover loss of the data for which error correction couldn't compensate. Since it is only fractions of a second, it was easy to trick the ear into thinking it was normal sound and not a patch to get past a drop-out. Can anyone verify that? Does Dolby D have a similar "replacement" technology?

I guess when you figure CDS had the entire optical track area to fill with digital information -- that's a pretty big chunk of geography -- they were confident that they didn't need the analog track as a backup. After all, CDs and DVDs don't need an analog backup.

And that leads me to another question -- given the relatively huge amount of space that the analog track covers (say 10,000 ft. x 1/8th in. for a typical film), how is it that all this compression is needed? Compared to that amount of area available on a typical print vs. the amount of area that a less than 5in diameter CD covers, a feature film is gargantuan compared to a compact disk. How did that happen?

Frank