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From: hal@cco.caltech.edu (Hal Finney)
Newsgroups: sci.crypt
Subject: Re: Let's build software cryptophones for over the internet...
Date: 25 Apr 1993 17:12:32 GMT
Organization: California Institute of Technology, Pasadena
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Message-ID: <1regq0INNn7u@gap.caltech.edu>
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gtoal@gtoal.com (Graham Toal) writes:

>I forwarded an old posting about CELP speech compression:
>[...]
>I've since been told that the source of this is on cygnus.com
>in /pub/celp.speech.tar.Z

>I'm not in a position to; any Sun tcp/ip gurus out there who think they
>can marry this with netfone by the end of the week? ;-)  Seriously.  I
>think someone with real net access and two sparcs could have this running
>by the end of the week.  Then we ask the pgp guys to add a bytestream
>crypto filter.  Two weeks at the most.  [Damn, I wish I had my sparc
>back... I'm stuck on a 25mhz 386sx]

I tried this code yesterday.  On my Sparcstation ELC it takes over
300 seconds to compress 22 seconds' worth of speech.  This means that it
needs to be "optimized" by over a factor of 10 before it will be usable
in even a half-duplex mode.

I question whether CELP is the best approach for this application.  It produces
great compression but at the expense of tremendous CPU loads.  We want
something that can be run on ordinary workstations or even high-end PC's
without DSP cards.  My guess is that some other algorithm is going to be
a better starting point.

Hal Finney
