Film-Tech Forum ARCHIVE: Capturing Dolby A, SR audio on a film scanner

This is topic Capturing Dolby A, SR audio on a film scanner in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Paul Gordon (Member # 3320) on 02-10-2015, 07:37 AM:

Bit of an odd question but maybe you guys can help.

Ok at work we have a film scanner that can also capture audio with a SONDOR soundhead (optical 35mm, 16mm, magtrip 16mm and fullcoat). The reader is redlight.

Most of time we are capturing older mono films, but sometimes we scan a Dolby A or SR title. The problem is the scanner will just create a 24bit stereo WAV file not a 4.1 track.

So how do we easily get the track decoded to 4.1? do we need to fit a dolby processor in the chain? a Cp-650 or something. The sound head is simply 2 balanced XLR's out.

I'll probably have to chat with SONDOR but figured someone here might have an idea.

Thanks!

Posted by Mitchell Dvoskin (Member # 751) on 02-10-2015, 08:28 AM:

Analog Dolby Stereo (both A and SR) only contain discreet left/right on the soundtrack. You will indeed need to feed the left/right on the film into a Dolby 45/65/500/650 processor to break out the center and surround channels.

Posted by Scott Norwood (Member # 30) on 02-10-2015, 08:54 AM:

A Dolby SDU-4 will do it.

Posted by Paul Gordon (Member # 3320) on 02-10-2015, 09:07 AM:

Scott will that also give me noise reduction?

Posted by Scott Norwood (Member # 30) on 02-10-2015, 10:48 AM:

No, it just does the matrix decoding. A 363 with cat 300s would do the NR, though. Or you could use a cinema processor. I believe that the CP650 has a non-sync format with SR NR that would work (or you could use the optical input if there is no preamp in the soundhead).

Posted by Paul Gordon (Member # 3320) on 02-10-2015, 11:21 AM:

Ok well the Sondor head does have a preamp so thats good to know. Does the 363 NR Frame go first in the chain, then the SDU-4?

-paul

Posted by Gordon McLeod (Member # 33) on 02-10-2015, 11:40 AM:

Probably the easiest would be to grab a CP65 with real SR cards and use it to decoded If the sondor has a left/right optical preamp one could go into the terminals on the back for optical preamp output and pull the NR cards
This would give you outputs of L R C S and SW the sub the SDU-4 will not provide Just jumper out the fade and eq stage

Posted by Paul Gordon (Member # 3320) on 02-10-2015, 12:04 PM:

Little confused Gordon. Are you saying you can bypass the preamp card on the Cp65 and still get NR and 4.1 decoding?
In the Cp-65 manual it says the unit may not work if the Cat 241 card is damaged.

-paul

Posted by Scott Norwood (Member # 30) on 02-10-2015, 12:09 PM:

Paul--right: 363 (you will need a Dolby cat. 69 loop to set levels) to SDU4.

But Gordon makes a good point--if you want a separate subwoofer channel, this option will not provide that.

Posted by Gordon McLeod (Member # 33) on 02-10-2015, 12:48 PM:

It should work I have done it with some older processors so i suspect it should work with that or find a Panastereo CSP1200 as it allows for the AUX to go through the NR chain

Posted by Paul Gordon (Member # 3320) on 02-10-2015, 12:59 PM:

Cool thanks. You don't happen to have one we can buy? either a CP65 with 350 SR cards or a Panstereo unit!

-paul

Posted by Mark Gulbrandsen (Member # 72) on 02-11-2015, 07:22 PM:

You will also have much cleaner sound and better SR noise reduction when needed with the CSP-1200!

Mark

Posted by Paul Gordon (Member # 3320) on 02-12-2015, 05:10 AM:

Love to find one but they seem very hard to find these days.

Posted by Carsten Kurz (Member # 5396) on 02-12-2015, 05:38 AM:

Don't stick to any specific device. CP65, CP500, still should be plenty of them around.
What's certainly more important is to find someone who is able to install and adjust it properly with the test-loops, etc. Optical sound is not plug'nplay or set-and-forget, it's delicate to adjust initially and needs some readjustment now and then.

What about Dolby Digital tracks? I know a german company operating their film scanning from an FP30D machine with both optical and SRD reader, into a CP500.

- Carsten

Posted by Paul Gordon (Member # 3320) on 02-12-2015, 08:31 AM:

Yes we have test loops and I've used CP55, 65's and 200's in a cinema setting. Sondor does make a Dolby Digital and DTS reader but currently we only have the analog head (optical and mag). 99.9% of the films we are scanning are pre-digital audio.

Posted by Leo Enticknap (Member # 534) on 02-12-2015, 09:01 AM:

MWA-Nova and Lasergraphics make 35mm digital optical readers for their scanners for everything except SDDS, too.

Posted by Paul Gordon (Member # 3320) on 02-12-2015, 09:42 AM:

Good to know but we are stuck with a DFT Scanity. Two years ago very few scanners (not telecines) had sound head capture options.

Posted by Paul Gordon (Member # 3320) on 03-16-2015, 05:41 AM:

Ok we found a decent CP-65 with Cat 350 SR cards. Our problem is the Sondor head on the scanner has a preamp and the stereo signal is way to hot. Any ideas of an easy solution. Is there a way to bi-pass the Cp-65 preamp card and still get NR and 4.1 out? Pulling the card does not seem to work as nothing flows through the other cards then. I'm going to talk to Sondor but jut though you guys may have a good idea. BTW this will be an issue with all film scanners. They may say they can capture Dolby A, or SR but all they do is give you an un-decoded stereo track with no NR!

Posted by Dave Macaulay (Member # 813) on 03-16-2015, 06:14 AM:

Pad it.
The analog optical track is only L/R, encoded with Dolby SR noise reduction.
It is usable without any decoding, applying A decoding eliminates some of the SR encoding artifacts, and SR decoding is ideal. Reader signal response and EQ is important, level matching is required.

Posted by Paul Gordon (Member # 3320) on 03-16-2015, 08:25 AM:

Yes we could pad the incoming hot signal but a jumper that bi-passes the preamp on the Dolby might be a better option. The difference in signal strength is huge like 50db

Posted by Louis Bornwasser (Member # 3063) on 03-16-2015, 08:52 AM:

Perhaps bypassing the Sondor preamp is the answer. The output of your red LED works directly into the Dolby input. It would look just like any other soundhead.

Posted by Steve Guttag (Member # 268) on 03-16-2015, 12:14 PM:

Unplug the CAT240A and then connect up to the Optical Preamp Outputs...you'll be at a 388mV buss level there. You can also come in on the "Mag" inputs and configure the CAT443 appropriately to get everything switched as you like.

Another handy trick that works with most any Dolby optical preamp is to use 47K resistors to each optical preamp terminal (one on the + and one on the -) to your source. They will knock down the level to approximately consumer level -10dBV. It is important that you use a resistor on each terminal and not just the + ones. Particularly on the CAT240A, which uses non-transformer inputs.