In typical Dolby Surround mixing, the material is mixed to 4 discrete
channels - Left/Center/Right/Surround. This 4 channel mix is fed to the
Dolby Surround Encoder which does the matrixing. I do not know the exact
nature of the phase shifting. BTW, Dolby Surround is a trademark, and, at
least some of the technology is proprietary. Much more information available
at http://www.dolby.com

Hope this helps.

David M. Boothe
 Audio Director
  Lyrick Studios
   Dallas, Texas USA


> -----Original Message-----
> From: Anders Andersson [mailto:pipe@algonet.se]
> Sent: Wednesday, September 16, 1998 12:52 PM
> To: -
> Subject: Dolby surround encode
> 
> 
> Hi, has anyone tried to encode dolby-surround sounds using 
> csound, or in any
> other ways?
> I have 3 questions regarding this:
> 
> When encoding the surround channel, do you HAVE to 
> phase-shift (+90/-90), or
> is it equal to doing (0/-180)?
> And do you have to use the Band pass filter when encoding the surround
> channel? I guess every decent dolby-decoder uses a LP-filter 
> for that channel
> anyway.
> Do you HAVE to use some dolby noise-reduction for the 
> surround channel? When
> using 100% digitally generated music (noise? ;), to deliver 
> 100% digitally,
> this would be obsolete, i guess.
> 
> 
> 
> .--- -- -  -
> | Anders "Pipe/Nature" Andersson, pipe@algonet.se
> :

A while back I was deep in studying Dolby Surround and AC3.  Here's a few
texts I found at Creative/Europe's site of all places, on AC-3 (which we
all know is far better than Dolby Surround anyway).  

http://www.cle.creaf.com/techknow/technology/dolby/ac-3mult.htm
**Has a great little graph at the bottom 

http://www.cle.creaf.com/techknow/technology/dolby/dolby.htm

Granted, these are basic documents, but give a good overview, history and a
little bit on the technical side.  I'm sure there are some better resources
out there, but I thought I might give a little input anyway.

I would LOVE to see CSound sucessfully implement this!

Christian Guirreri
cguirrer@runet.edu

At 05:44 PM 9/17/98 -0500, you wrote:
>In typical Dolby Surround mixing, the material is mixed to 4 discrete