🚀 go-pugleaf

 MSG:FROM: SPGDCM  --UCBCMSA  TO: NETWORK --NETWORK           11/16/88 20:03:18
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 From: Doug Mosher
 Subject: more than 2 channels encoded into 2.

 To: sci-electronics@ucbvax

 I was suprprised to see the extended discussion about how to get a center
 channel in this group, where ever so many people talked in terms of
 algebra and the impossibility of expressing more than two variables with
 only two channels.

 It's a regular thing to do this in, for example, Dolby Surround.
 I quote another contributor:
 jay@ncspm.ncsu.edu (Jay C. Smith) wrote, in rec.video:
 >Dolby Stereo encodes four channels into two.
 >The two channels are Left and Right, with encoded channels Center (or Dialog,
 >L+R) and Surround (or Rear, L-R).  There's some other processing going on,
 >too, but that's basically it.  The only films I know of that use left and
 >right rear channels are the 70mm six-track "Apocalypse Now" (1979, the
 >first film to use directional rear channels) and Lucasfilm's THX six-track
 >process.  Neither of these are available in two-track form with encoded
 >rear channels (accent on the plural), to my knowledge.
 >
 >There may be processors available that synthesize such channels from Dolby
 >Stereo, but they aren't Dolby Stereo, and it's questionable what effect
 >they have on the originally intended sound.  We already have enough
 >problems with Dolby's loose licensing of "official" home Dolby equipment
 >that are of wide-ranging degrees of quality.

 Now, this type of encoding must have been done on the original; there isn't
 a way to "decode" such things as a center channel from a recording that wasn't
 encoded, at least not using this method.

 But it points out a sort of logical blind spot. The rec.video and rec.audio
 people are familiar with these facts, but it somehow isn't as well known
 in sci.electronics.

 (                                                            )
 (          Doug Mosher <SPGDCM@CMSA.Berkeley.edu>            )
 (                      ...!ucbvax!cmsa!spgdcm                )
 ( 257 Evans, Univ. of California, Berkeley, CA, 415/642-5823 )
   ;  more than 2 channels encoded into 2.