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From: jaw@riacs.edu (James A. Woods)
Newsgroups: comp.compression
Subject: arithmetic coding patents (was, Re: A rather naive request.)
Message-ID: <1991Apr2.025746.13749@riacs.edu>
Date: 2 Apr 91 02:57:46 GMT
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>>If you ignore the many patents on arithmetic coding, that is.

>Be more specific. List the "many patents" on arithmetic coding [...]

from the cassis patent cd-rom system, here are the last five patents
containing the keywords "arithmetic" and "coding" in the title:

	#4905297    Arithmetic coding encoder and decoder system

	#4891643    Arithmetic coding data compression/de-compression by
		    selectively employed diverse arithmetic coding encoders
		    and decoders

	#4467317    High-speed artihmetic compression coding

	#4286256    Method and apparatus for arithmetic coding utilizing
		    a reduced number of operations

	#4122440    Method and means for arithmetic string coding

three of the five have glen langdon as an inventor (and assignee ibm corp.)
the latest was granted feb. 27, 1990 and represents much of the adaptive
coding work of langdon, mitchell, pennebaker, and rissanen discussed
in a special issue of the ibm j. r. & d.

i have not read through the claims, but much of q-coding (as they dub
their tuned implementation of arithmetic coding) seems to involve replacement
of multiplications by shifts.

many of us hope that none of these patents would sandbag any efforts
of the joint photographic committee, where arithmetic coding is used
in the lossless mode specification.  as with 'compress', it is too late
to reign in actual public domain code, which tends to be developed
independently of any patents.