Path: utzoo!utgpu!watmath!xenitec!zswamp!p0.f171.n221.z1.fidonet.org!Geoffrey.Welsh
From: Geoffrey.Welsh@p0.f171.n221.z1.fidonet.org (Geoffrey Welsh)
Newsgroups: comp.dcom.modems
Subject: Re: Request for information (again)
Message-ID: <998.251E4CDB@zswamp.fidonet.org>
Date: 25 Sep 89 15:40:55 GMT
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 > From: carr@gandalf.UUCP (Dave Carr)
 > Message-ID: <2608@gandalf.UUCP>
 
 > ACT CommPressor software (rights to reproduce) go for about $3,000 US.
 >
 > Now the funny part.  CCITT called for papers to standardize modem
 > compression (V.42 bis).  Microcom leapt up and said "Pick me. Pick me".
 > ACT and most other modem manufacturers said "Pick us".  But alas, CCITT
 > picked a modified Limpel-Ziv (Unix compress,etc) from British Telecom.
 
   Not funny at all. The CCITT V.42bis committee cited problems with MNP5 (may 
EXPAND the data if it's already been compressed), MNP7, and ACT (they're 
proprietary; the CCITT won't adopt anything that won't become PD).
 
 > So, expect the new breed of modems to get about 4:1 compression!
 
   I'm not sure it will be that high. I know that it's possible (the latest 
version of PKZIP will compress a text file to 15-20% of its original size), 
but compression "on the fly" is less powerful, especially if you don't want 
to incurr big delays by keeping enough data in memory to make powerful 
analyses on them before sending them off.
 
 > I'll bet the Telebit uses ACT CommPressor software.
 
   Quite possible, but I don't think the TB+ compression algorithm gets 
significantly better ratios than MNP5.



--  
Geoffrey Welsh - via FidoNet node 1:221/171
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