R/E/P Community

Please login or register.

Login with username, password and session length
Advanced search  

Pages: [1]   Go Down

Author Topic: Software decoding of Dolby NR recordings???  (Read 3755 times)

breathe

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1104
Software decoding of Dolby NR recordings???
« on: January 21, 2011, 08:27:55 am »

Here's one for ya!  1/2" 16-track tape encoded Dolby C or S, transferred to digital with NR turned off.  How do you decode this recording?

Nicholas




Logged

ssltech

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 4780
Re: Software decoding of Dolby NR recordings???
« Reply #1 on: January 21, 2011, 10:53:47 am »

Pay someone to write a plug, or transfer to a SECOND DAW (or whatever) while transfering the analog through a decoder.

Hope you copied the tones over, or your Dolby Level is lost.

Keith
Logged
MDM (maxdimario) wrote on Fri, 16 November 2007 21:36

I have the feeling that I have more experience in my little finger than you do in your whole body about audio electronics..

DarinK

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 410
Re: Software decoding of Dolby NR recordings???
« Reply #2 on: January 21, 2011, 01:49:44 pm »

ssltech wrote on Fri, 21 January 2011 07:53

Pay someone to write a plug, or transfer to a SECOND DAW (or whatever) while transfering the analog through a decoder.

Hope you copied the tones over, or your Dolby Level is lost.

Keith


I did a lot of work with a Fostex 1/2" 16 track back in the 90s.  No tones or adjustments without opening the whole thing up. (It was not meant to be aligned by the user.)  It may have had some sort of Dolby but I don't remember if it was C or S.  It may have been globally defeatable with a switch on the back.

Your best bet, which is probably not an option, is to have the transfer re-done using whatever specific machine was used to record it in the first place.

Logged

breathe

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1104
Re: Software decoding of Dolby NR recordings???
« Reply #3 on: January 21, 2011, 04:48:14 pm »

It's hard enough having one 1/2" 16-track machine, it's pathetic to have to have ones for Dolby C, Dolby S, and DBX decoding!  The worst part about tapes encoded with "prosumer" NR is they didn't really make outboard decoders for these formats.  Dolby makes (I think the 422) which can decode Dolby C and S but it's a 2-channel unit and it costs a fortune.  I wonder if you could hack a Fostex 1/2" 16-track and make the Dolby part a separate unit.  DBX I'm also unclear about.  Is the DBX in Tascam and Yamaha cassette 4/8-tracks the same as in the Tascam 388 and Tascam 1/2" 16-tracks and 8-tracks, as well as the ATR-60 1" 16-track?  The same as the DBX 911 module?

Nicholas
Logged

Galil

  • Full Member
  • ***
  • Offline Offline
  • Posts: 122
Re: Software decoding of Dolby NR recordings???
« Reply #4 on: January 21, 2011, 05:42:44 pm »

There were two types of DBX noise reduction. Type I was used on pro tape recorders while type II was used on broadcast cart machines, cassette decks, etc. Like the Dolby systems (or even more so), they were fairly picky about alignment issues on tape decks.

Porta-studios used type II while Tascam open reel recorders used type I.  I believe that both type I and type II cards were made for DBX 900 racks and they should be fairly cheap now since there is very little call for them.

Galil
Logged

Dominick

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 580
Re: Software decoding of Dolby NR recordings???
« Reply #5 on: January 21, 2011, 06:21:39 pm »

 re dbx alignment, (at least for dbx type I)

dbx type I is a 2 to 1 compander that adds pre emphasis to the record signal before the compressor and de emphasis on the playback signal after expansion.

Calibration of the tape machine was critical. Any error in the tape machine's record to play alignment was doubled. Because of the pre emphasis, you had to be very conservative with the level going to tape. The more you slammed level to tape, the murkier it would sound after decoding.  In their operation manuals, dbx cautioned users that the loudest program peaks should never exceed 0VU record levels.

Unlike Dolby NR, dbx NR works the same on the quietest to loudest signals.
The only reason the dbx units had cal pots was for unity gain.
You could use a dbx decode unit that is many dB out of alignment.
Unless it's input is being clipped, aside from level matching being off, there would be no error in the decoding of the signal.
Logged
Dominick Costanzo
Pages: [1]   Go Up