Film-Tech Forums: 70mm sound

»	Film-Tech Forums » Film Handler's Forum » 70mm sound

Author

Topic: 70mm sound

Stephen Furley
Film God

Posts: 2488
From: Coulsdon, Croydon, England
Registered: May 2002

posted 11-12-2002 04:19 AM

On the one occasion that I have run 70mm, many years ago now, it was the original Todd-AO format, five screen channels, mono surround, no NR.

I am totally confused about the later formats, much of what I have read seems to be conflicting.

Can someone please give me a list of all magnetic formats which have been used on 70mm, format numbers, noise reduction, channel assignments, and which processors, and/or outboard adapters are needed to play them.

I assume that DTS on 70 is the same format as on 35.

What about CDS, were all CDS readers dual guage, the one I have seen was, or were there any 35 or 70 only versions? Was the sound format the same for both guages? How many channels was it?

Thanks.

| IP: Logged

Thomas Hauerslev
Master Film Handler

Posts: 321
From: Copenhagen, Denmark
Registered: Aug 2000

posted 11-12-2002 05:00 AM

Please find Dolby Stereo format codes here

------------------
Cheers, Thomas
here
here
here

| IP: Logged

Bobby Henderson
"Ask me about Trajan."

Posts: 7416
From: Lawton, OK, USA
Registered: Apr 2001

posted 11-12-2002 07:01 PM

CDS was a 5.1 channel system. The sound format was the same for both systems, however a different sound negative was developed for the 35mm version, which packed the data into a somewhat smaller space than was available on 5-perf 70mm. The level of quality for high speed 35mm film printing and CCD imagers didn't do too well for the demanding, data intensive CDS audio track. Perhaps if the same situation were to play over again today in 2002, CDS might have stood a better chance.

Both 70mm and 35mm versions packed a staggering amount of 1-bit Delta Modulation encoded audio onto the track. Data ran in the neighborhood of 6 million bits per second. That's way above the total data rates of SDDS (2.2Mb/s), Dolby Digital (556kb/s) and DTS (820kb/s).

DTS is the same regardless of film gauge since the separate CDs hold the sound. The only thing that changes is the type of reader and time code depending on film gauge and format.

| IP: Logged

Steve Kraus
Butt God

Posts: 3666
From: Chicago, IL, USA
Registered: May 2000

posted 11-13-2002 01:51 AM

CDS was the same on both 35mm and 70mm except for data bits being 1.25X stretched vertically on the 70mm version due to the greater linear speed. Although the 70mm version was introduced first I think it is fair to say the 70mm dots were stretched as opposed to saying the 35mm dots were compressed since they were square on 35mm (14 x 14 microns) but rectangular on 70mm (17.5 x 14 microns). The CCD reader would "see" both tracks as being exactly the same.

[Hmmm...does this predate and therefore invalidate that Dolby patent that seems to cover any digital sound system whose data simply gets stretched out on 70mm but is otherwise the same?]

I believe the production model penthouse readers were all dual gauge.

A web version of the CDS brochure with specs may be found here

| IP: Logged

Ray Derrick
Master Film Handler

Posts: 298
From: Sydney, Australia
Registered: Sep 2001

posted 11-15-2002 05:24 AM

[Hmmm...does this predate and therefore invalidate that Dolby patent that seems to cover any digital sound system whose data simply gets stretched out on 70mm but is otherwise the same?]

Well Steve, if it does, it wouldn't be the first time. The US Patent Office is littered with patents that have managed re-patent prior art. Obviously they, unlike the Swiss Patent Office, do not employ people of the calibre of Albert Einstein to examine patent applications.

------------------
Ray Derrick
President/Chief Engineer
Panalogic Corporation Sydney, Australia
Phone: 61 (0)2 9894 6655 Fax: 61 (0)2 9894 6935

| IP: Logged

Jeffry L. Johnson
Jedi Master Film Handler

Posts: 704
From: Cleveland, Ohio, USA
Registered: Apr 2000

posted 11-16-2002 11:30 AM

here is a Film Sound Formats table from the Film Sound History Web site.

| IP: Logged

Dick Vaughan
Jedi Master Film Handler

Posts: 963
From: Bradford, West Yorkshire, UK
Registered: Jul 2000

posted 11-18-2002 03:18 AM

The table you linked to is slightly in error as the Cinerama sound format does not show the back wall channel.

| IP: Logged

All times are CT (US)

Printer-friendly view of this topic

Copyright 1999-2010 Film-Tech Cinema Systems, LLC

Powered by Infopop Corporation
UBB.classic^TM 6.3.1.2
The Film-Tech Forums are designed for various members related to the cinema industry to express their opinions, viewpoints and testimonials on various products, services and events based upon speculation, personal knowledge and factual information through use, therefore all views represented here allow no liability upon the publishers of this web site and the owners of said views assume no liability for any ill will resulting from these postings. The posts made here are for educational as well as entertainment purposes and as such anyone viewing this portion of the website must accept these views as statements of the author of that opinion and agrees to release the authors from any and all liability.