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From: roy@esp.ics.uci.edu (John Roy)
Newsgroups: comp.dcom.modems
Subject: Re: Data Compression
Message-ID: <269DE3BD.28935@ics.uci.edu>
Date: 13 Jul 90 15:07:42 GMT
References: <3505@hsfmsh.UUCP>
Lines: 28

In <3505@hsfmsh.UUCP> tnixon@hsfmsh.UUCP (Toby Nixon) writes:
>I can go into this in more detail if you like.  But remember this
>essential difference:  MNP5 takes FIXED-LENGTH objects and sends
>them using a VARIABLE-LENGTH code; V.42bis takes VARIABLE-LENGTH
>objects and sends them using a FIXED-LENGTH code.

>The actual throughput you see is dependent on the redundancy
>(compressibility) of the data.  The 2-to-1 and 4-to-1 are for
>English text (like this; lower-case, lots of spaces, fairly normal
>vocabulary, etc.)  If you're sending binary files or
>previously-compressed data (like news feeds), you won't see that
>level of compression (if any).  But for interactive work, the
>compression definitely is an advantage.

>	-- Toby

So if I'm sending ASCII digits would I do better with MNP5 or V.42bis?
I would guess MNP5, but...

Yes, I know this could be done by translating into binary or even BCD
and then compressing.  But if I can get similar results by just
purchasing the right modem, I'd be happy.

jmar
--
John M.A. Roy 714/856-5039			TRINTECH USA 714/757-7757
ICS Dept., Univ. Calif., Irvine CA 92714	18500 Von Karman, #410
Internet: roy@ics.uci.edu  			Irvine, CA 92715