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Topic: "Cinema Digital" sound

Aaron Sisemore
Flaming Ribs beat Reeses Peanut Butter Cups any day!

Posts: 3061
From: Rockwall TX USA
Registered: Sep 1999

posted 04-01-2002 01:15 AM

Laurie Anderson's 'Home Of The Brave' was also done via a VHS-recorded digital track synced to a 35mm print.

-Aaron

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John Pytlak
Film God

Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000

posted 04-01-2002 12:35 PM

Bobby Henderson said: "I've never been able to find out for sure just what the bitrate was for CDS"

The details were given in the SMPTE papers "Cinema Digital Sound -- The Technology" and "Cinema Digital Sound -- System Overview", by Howard J. Flemming and Ronald E. Uhlig, presented at the 132nd SMPTE Technical Conference in October 1990. For 35mm prints, the raw bit rate was 5,850,000 bits per second. Each bit was 14 x 14 micrometres in size, with 180 columns of bits across the track, and 32,500 rows of bits in each second (24 frames) of film.

------------------
John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Research Labs, Building 69, Room 7525A
Rochester, New York, 14650-1922 USA
Tel: +1 585 477 5325 Cell: +1 585 781 4036 Fax: +1 585 722 7243
E-Mail: john.pytlak@kodak.com
Web site: http://www.kodak.com/go/motion

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Bobby Henderson
"Ask me about Trajan."

Posts: 10973
From: Lawton, OK, USA
Registered: Apr 2001

posted 04-01-2002 09:20 PM

Holy Moly! 5.8 million bits per second!? That's a lot more data than the loose "4:1" claims on data compression ratio I had heard. That kind of bandwidth is more than double the 2.2 million spots total per second used by SDDS (and only 1.2 million are used in the primary soundtrack for SDDS). CDS' 5.8Mb/s is actually more than the 4.6Mb/s needed for a 16-bit/44.1kHz audio track featuring 6 full bandwidth channels. But I am assuming all the extra data is needed for error correction.

Those fellows at ORC sure had some guts by printing digital audio tracks with that much data. Limits on film printing certainly introduced problems, but CCD imagers back in 1990 were nowhere near the level of sophistication and speed we see today. It kind of makes me wonder how reliability would be improved with a new CDS reader designed with current CCD electronics.

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John Pytlak
Film God

Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000

posted 04-02-2002 07:18 AM

I recall that Kodak's Ron Uhlig worked closely with film laboratories to assure that the CDS tracks could be printed reliably. Putting the bits in the analog soundtrack area minimized any wear during projection. The lack of analog backup and the dual print inventory issues were problematic. Yet CDS paved the way for today's digital sound systems.

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Steve Kraus
Film God

Posts: 4094
From: Chicago, IL, USA
Registered: May 2000

posted 04-02-2002 06:55 PM

The raw bit rate (180 x 32,494 = 5,848,920 b/s) includes Reed-Solomon error correcting codes which adds quite a bit of overhead. The CDS specs claimed the main channels were the equivalent of 16-bits/sample, 44.1K samples/sec. That works out to 3,528,000 bits per second. I'm not sure about the sub channel but let's say it's half the sampling rate and half the bits per sample. That brings us up to 3,704,800. Add some auxilary data bits and the error correcting code makes up the balance.

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Joe Redifer
You need a beating today

Posts: 12859
From: Denver, Colorado
Registered: May 99

posted 04-02-2002 08:25 PM

Here is a picture of the HUGE CDS reader. This thing weighs more than you do.

And below is the only picture I could dig up of the massive "rack mounted" decoder (the grey unit). It bears many similarities to SDDS, actually.

One time Brad and I actually got this thing to boot up. It was an amazing moment! Nowadays this same technology could be built to be 1u high! Maybe 2u if you really need all those buttons.

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Brad Miller
Administrator

Posts: 17775
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99

posted 04-02-2002 10:42 PM

Huge is hardly the word for CDS. Joe isn't kidding about how unnecessarily heavy that reader is. I'll try and remember to take some pictures of the guts of the processor and reader and post them soon.

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Steve Kraus
Film God

Posts: 4094
From: Chicago, IL, USA
Registered: May 2000

posted 04-03-2002 08:49 AM

THE Actual Joe Redifer said:
>It bears many similarities to SDDS, actually.

I believe Howard Fleming of CDS was the primary designer of SDDS. As for the reader, they designed it they way they thought a projector penthouse ought to be designed starting with a cast metal housing just like a 6 or 4 track magnetic penthouse.

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