Newsgroups: sci.engr.television.broadcast
Subject: Re: Why no Sony 5.1 sound on VHS?
References: 
From: Tomi Holger Engdahl 
Date: 06 Apr 2000 15:57:24 +0300
Message-ID: 
Organization: Helsinki University of Technology, Finland
Lines: 67
X-Newsreader: Gnus v5.6.45/Emacs 19.34
CJ's Dad  writes:

> Is there a technical reason why a VHS vcr can't reproduce the 5.1
> sound field? 

Yes there is. A normal VHS VCR has only one 1 mono audio track,
which has poower sound quality than C-casette. Hifi VCRs have
in addition to that two channels (=1 stereo) of HIFI quality
audio. When playing back tapes using HIFI VCR, it plays back
only those HIFI sound channels (if they do not exist then it used
that poor old mono sound). 

Because the normal VCR does have only two analogue channels of audio, 
it can't store 6 separate audio channels in any way so that they could
be also spearated back to separate channels on the playback. 
Norma VCR does not have any provision to store that 5.1 audio
format in the original digital format either, because it does not have
any provision to store digitla data to the tape. 

So you have to say goodbuy to the original 5.1 sounds on VCR.

> It sounds so great on Directv, just wondering why the lowly VHS format
> can't do it.

VHS format can't do that. The best it can do is one HIFI quality stereo
track to which you can store a Dolby Surround audio track (it takes
only one stereo track). Dolby surround system has front channels and one 
background channel all coded to one analogue stereo sound track. The
coded audio can be separated using Dolby Surround capble amplifier.
Because of the limitations of that coding, the surround sound is never
as good as with 5.1 system, but something usable better than normal
stereo.  

So to get some thing which somewhat resembles the original 5.1 surround
you would have to convert the 5.1 channel sound to Dolby Surround
before storing it to the audio channels of the VCR and playback
it through a Dolby Surround amplifier. This makes some usable
solby surround, but does not give the clarity and details
of the original 5.1 sound.

how to do that coding from 5.1 siunds to Dilby Surround is another question.
I don't know any separate boxes for doing that. For DVD players I know
that practically all of them have built-in converters such that
the 5.1 sound on the DVD disc can be transcoded to Dolby Surround
sound output from the normal analogue stereo output. For your Directtv
I don't know what would be thr most practical solution to your case.

For more information different surround audio formats take a look at
the links at www.epanorama.net audio section.

-- 
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at 
http://www.epanorama.net/