From: Timothy Newsham <newsham@wiliki.eng.hawaii.edu>
Date: Fri, 10 Dec 93 19:54:18 PST
To: mg5n+@andrew.cmu.edu (Matthew J Ghio)
Subject: Re: LPC for speech (fwd)
In-Reply-To: <oh2G43C00awT41wlM9@andrew.cmu.edu>
Message-ID: <9312110351.AA08586@toad.com>
MIME-Version: 1.0
Content-Type: text/plain


> 
> <jp12745@coewl.cen.uiuc.edu>jerry@terminus.us.dell.com> wrote:
> 
> > Did you know that using LPC (linear predictive coding) on
> > speech can near-telephone quality at only 8 k BITs/second?
> > With a signficant decrease in quality (but still very
> > understandable... probably better than radio) you can get
> > the rate down to 2kbps.  If you don't mind sounding like
> > a speak&spell, you can go to 600bps or less.
> 
[...]
> 600bps is not realistic.  Most people can READ text faster than 600 bps
> (okay it's a little above average, but not if you were skimming; to give
> you a rough estimate, it's a little slower than reading one line per
> second)  You just can't expect to cram all the intricacies and
> inflections of speech into a 600bps channel and be understood.  But why
> sacrifice quality when you can use a 14400bps modem?  They aren't all
> too expensive these days.

600 bps is not realistic?  Voice has been gotten down to 400 to 600bps
by doing some coding on the output of a LPC (pitch + gain + filter
parameters) and transmitting that.  The remote decodes to recover
LPC parameters and uses that to synth speech.  The quality is supposed
to be the same as 2400 bps LPC (slightly synthetic sounding,  definitely
not 'toll quality').