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From: wlrc@neoucom.UUCP (William Cruce)
Newsgroups: net.video,net.audio
Subject: Re: MTS stereo decoders ?
Message-ID: <309@neoucom.UUCP>
Date: Mon, 27-Oct-86 12:25:26 EST
Article-I.D.: neoucom.309
Posted: Mon Oct 27 12:25:26 1986
Date-Received: Tue, 28-Oct-86 01:50:50 EST
References: <368@cord.UUCP> <1372@uwmcsd1.UUCP> <587@rdin.UUCP> <307@neoucom.UUCP>
Organization: Northeastern Ohio Universities College of Medicine
Lines: 45
Xref: watmath net.video:3551 net.audio:9838
Summary: Noise reduction degrades Hi Fi VCRs There are two kinds of Dolbys on Videotape


There are several reasons why noise reduction is needed for
the audio FM (Hi Fi) signal in both Beta and VHS VCRs, not
the least of which is to reduce the switching noise which
occurs at the end of each video frame (a recent issue of 
Stereophile magazine has a pretty good discussion of the
subject).  Unfortunately both Sony (Beta) and JVC (VHS) 
developed their own noise reduction systems instead of
licensing from someone like DBX or Dolby who know what they're
doing.  The noise reduction systems do terrible things to the
sound, especially evident on sounds with high frequency
transients - cymbals, tamborines, wood blocks - but generally
pretty nasty to lots of musical sounds.

Dolby noise reduction is used on the linear track of some VHS
VCRs - those that split the linear track in two in order to
get stereo (the track becomes so small that noise reduction
was mandatory even when listening over a TV set).  Beta never
marketed a VCR with stereo linear tracks in the USA, although
I understand they did in Japan and/or Europe.

Dolby also has a system or systems for creating "surround
sound" in movie theaters (the system incorporates dolby noise
reduction for the rear channels).  Any movie which has the
Dolby logo in the credits at the end  probably has the
surround sound information encoded in the stereo tracks
exactly as it is for 35mm theatre films (70mm uses a different
Dolby surround sound system with discrete tracks for the extra
channels).  I don't think any VCRs are available which will
decode the surround sound signal directly.  But if you have a
HI FI VCR (possibly it would work with a VHS Stereo Linear
track) and add on a Surround Sound Decoder (ones with the
Dolby logo will adhere to certain standards which probably
assure a better decoding of the signal - though there are
non-proprietary ways of extracting the information) you can
get surrround sound (extra speakers required, some decoders
have built in rear channel amps).

THE QUESTION:  Does anyone out there have hands on experience
with the various decoders?  Which has cleanest sound?  Which
does the best job of creating "surround sound".

Bill Cruce, N.E. Ohio Univs. College of Medicine
:
:wq