SPGDCM@CMSA.BERKELEY.EDU (11/17/88)
MSG:FROM: SPGDCM --UCBCMSA TO: NETWORK --NETWORK 11/16/88 20:03:18 To: NETWORK --NETWORK Network Address 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.