Dolby SR, anyone know about it?

farss wrote on 5/1/2005, 3:10 AM

I've got a heap of old 1/4" tapes to transfer and the labels say they're encoded with Dolby SR. A quick Google shows that this was an old Dolby encoding system that is now defunct. I'm wondering if I could simulate what the decoder would have done using some form of multiband dynamics, it'd help if I knew just how the system worked of course.
Overall I'm not too worried about this, the recordings are only of speech and they sound pretty much OK coming off the tape clean.
If anyone can shed some light on this would be much appreciated.
Bob.

Comments

MarkWWW wrote on 5/1/2005, 3:55 AM

Well, DolbySR (Spectral Recording) is old-ish (introduced in 1986 I think) but it's far from defunct - it is still the standard noise reduction scheme used on the analog soundtrack of films for cinematic release and is still alive and well in audio recording studios when using to analog recorders. DolbySR was the successor to original Dolby professional noise-reduction scheme (DolbyA) and the domestic DolbyS scheme (the successor to DolbyB and DolbyC) was based on a simplified version of the principles used in DolbySR.

Dolby publish some very good explanations of the way the systems work on their website in particular you might be interested in http://www.dolby.com/assets/pdf/tech_library/33_SpectralRecordingPaper.pdf which is a description of what's involved in DolbySR and http://www.dolby.com/assets/pdf/1000_kens_corner.pdf which is a general discussion of how noise reduction works in principle and how it is applied by the Dolby schemes.

I suppose in theory this information might be enough for you to simulate the decoding process, but in practice I don't think it's really on. But best of luck.

Mark

farss wrote on 5/1/2005, 6:48 AM

Thanks for that, interesting read!
Now if only I can find a second hand Model 363!

Bob.

Geoff_Wood wrote on 5/1/2005, 3:52 PM

No trouble - got a pair for US$150 complete with SR cards ! And just picked up a pair of A cards on eBay for $44.

SR is not 'old' in the sense is is the most recent/current/best anaolgue tape noise reduction system.

I've been waiting for years for somebody to come up with plugins, but I suspect they've never happened because Dolby is pretty shrewd wrt intellectual property and licencing.

geoff

tazio wrote on 5/1/2005, 7:08 PM

Hi there Bob,

I used to love the sound of Dolby SR, great NR and beautiful warmth. You'll most probably be right doing just voice, if there's any hiss, just roll-off. Bring a tape round if you'd like and we'll check it out for you.

How old are the tapes and are they shedding badly, you may have to get them baked.

I've found another candidate for SVUG

Phil

farss wrote on 5/2/2005, 1:41 AM

Hi Phil,
physically the tapes are in good nick, about 1988 vintage, recorded on good Ampex media. I think I've found a SR decoder we've had for years. Turns out they're built into our vintage 1" VCRs.

The hiss thing is kind of funny, most of what's there was in what was being recorded and not from the tape.

Bob.

fultro wrote on 5/2/2005, 12:10 PM

or it could be an artifact of the SR not being decoded - you might try some of SF noise reduction or WAVS if you have them
I have successfully used even broader band program without the Dolby B that it was encoded with - a bit of expansion I believe helped along with judicious eq - it actually became a pretty hot sounding track - you could still here the compression at work -

newhope wrote on 5/3/2005, 4:01 AM

Farss and Phil
Might be able to source a 363 for temporary SR decode at Aunty.... my son is mixng there these days and I freelance with them regularly. I'll ask next time I'm in.... Memphis Trousers on Saturday....
Now that should confuse the non OZ readers... LOL

Sorry to the rest of you....

Phil apologies for not contacting you this week ... double shifting between my own video and some Disney post at ATN.

farss wrote on 5/3/2005, 4:14 PM

I've got the job in the can but I'm still hoping I can find a 363 to add to my kit. Would have thought there was a few of them around after Aunty flogged off all her analogue gear. I probably saw some at the auctions and didn't realise what they were, damn.
Bob.

farss wrote on 6/21/2005, 7:20 AM

Well I finally got my 363, hooked it up to a deck today and played out a 15ips master tape recorded with SR, someone remind me again why we went digital. Damn it all the tape's gotta be 20 years old and it still sounds as good as anything done today.
Bob.

adowrx wrote on 6/21/2005, 7:27 AM

Tape does Rock,
Good News!!

http://www.quantegy.com/pressrelease.asp

farss wrote on 6/21/2005, 8:24 AM

Now that is good news, I was thinking they might have been gone for good.
Bob.