Article View: comp.compression.research
Article #108Re: arithmetic coding
From: Urban Koistinen
Date: Mon, 16 Nov 1992 11:27
Date: Mon, 16 Nov 1992 11:27
27 lines
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1553 bytes
In article <Nov.15.22.54.42.1992.14006@pepper.rutgers.edu> phalke@pepper.rutgers.edu (V. Phalke) writes:
Supposing SIGMA = { 0, 1}
If the probability P(0) is very high and P(1) is close to ZERO arithmetic
coding doesn't seem to work !!
I mean supposing the string is pure ZEROES then arithmetic coding interval
will decrease very slowly. This would result in a very long encoding. On
the other hand the entropy of this data is very low!!
Any help ??
If the interval doesn't decrease much, few bits need to be sent
giving good compression.
Many bits in, few bits out.
phalke@paul.rutgers.edu (908) 878-1602(h) (908) 932-4635(o)
The great thing about arithmetic coding is that if you know how to
calculate the probabilities for the next character, you get a code
that is very near optimum.
The bandwith wasted by the encoding scheme is only about exp(-N*log(2))
per bit encoded.
(N is the number of bits used by the coder)
This mean, the quality of compression depend only on the statistical
model.
--
Urban Koistinen - md85-epi@nada.kth.se
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Newsgroups: comp.compression.research Path: arc1-ca.pugleaf.net!sparky!uunet!mcsun!sunic!kth.se!hemul.nada.kth.se!md85-epi From: md85-epi@hemul.nada.kth.se (Urban Koistinen) Subject: Re: arithmetic coding Message-ID: <1992Nov16.112726.4493@kth.se> Keywords: when does it work ? Sender: usenet@kth.se (Usenet) Nntp-Posting-Host: hemul.nada.kth.se Organization: Royal Institute of Technology, Stockholm, Sweden Date: Mon, 16 Nov 1992 11:27:26 GMT Lines: 27