Film-Tech Forum ARCHIVE: stupid video-tech question

This is topic stupid video-tech question in forum Film-Yak at Film-Tech Forum ARCHIVE.

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Posted by Scott Norwood (Member # 30) on 08-12-2003, 07:58 AM:

At a festival, I recently got a Beta SP tape of something that was shot on film. The label on the tape said "Dolby SR." Now, I'm not super-knowledgeable about video stuff like Ian or Joe or others here, but my understanding is that Beta SP sound uses Dolby C-type NR by definition. This can be turned off, of course, but decoding SR would require an outboard decoder, which I didn't have.

I'm guessing that this was a mistake in the label because whatever 35mm prints may exist are probably Dolby SR encoded, and that the tape itself was supposed to be played back without outboard NR and (ideally) decoded through a Dolby-style L/C/R/S matrix. It sounded fine when played back with Dolby C-type NR through L/R channels only, but I'm still confused.

Has anyone ever seen a Beta SP tape with Dolby SR noise reduction?

Posted by Ron Lacheur (Member # 1126) on 08-12-2003, 09:31 AM:

I've seen some VHS tapes released by the big studios with " Dolby SR " on them. Hell, " Dolby Digital " is on my Speed 2 Cassette.

I don't think SR was designed for anything other than optical soundtracks on film.

But I could be wrong.

Posted by Pete Naples (Member # 761) on 08-12-2003, 10:19 AM:

Yup, seen plenty of Umatic SP and Beta SP with the audio tracks encoded with Dolby SR. Not always pro-logic encoded either.

There is no reason you couldn't put SR on cassette tape, VHS or BetaSP for that matter. You'd need to disable the decks on board NR & auto gain, and use external NR modules, having algined the record levels to dolby ref. Of course you'd need compatible NR modules for playback, but if you were replaying through a CP this wouldn't be tricky.

Posted by Bill Gabel (Member # 1105) on 08-12-2003, 01:26 PM:

quote:
I'm guessing that this was a mistake in the label because whatever 35mm prints may exist are probaly Dolby SR encoded, and that the tape itself was supposed to be played back without outboard NR and (Ideally) decoded through a Dolby-style L/C/R/S matrix.

We run a lot of film and video here. Did the tape say anything else about the tracks like stereo, Lt/Rt. A lot times during post and the mastering of video for screenings. They use SR as
a NR for different video formats like Beta/SP. If that label stated SR, they it should have been played back with SR. But thats only if you have the right equipment. A lot of the post houses label tape alittle differently sometimes. Sometimes tapes will be labeled Stereo with no NR or Stereo with NR. If it was labeled Lt/Rt then you would play it back using a Dolby-style matrix. Some Lt/Rt's are labeled to use SR NR and some say use
without SR NR. It all depends on what the tape label says. Because sometimes video tapes are not the final soundtrack like in film. It maybe just a Temp mix of the film. I handle many projects going through Post-Production that use many different sound to video formats.