From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: * X-Spam-Status: No, score=1.4 required=5.0 tests=BAYES_50,INVALID_MSGID autolearn=no autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 103376,b37ee187e035b961 X-Google-Attributes: gid103376,public From: jm59@prism.gatech.edu (John M. Mills) Subject: Re: LZW Date: 1998/02/18 Message-ID: <6cf4j0$fng@acmex.gatech.edu>#1/1 X-Deja-AN: 326276577 References: <6ca326$f0g$1@news4.isdnet.net> <34ea2f93.1444559@news.onramp.net> Organization: Georgia Institute of Technology Newsgroups: comp.lang.ada Date: 1998-02-18T00:00:00+00:00 List-Id: haseltine@onramp.net (Doug Haseltine) writes: >"Vicious" wrote: >>Anyone can tell me where I can find LZW ada source? >Sir: >We did a search a couple years ago when we had a such a need >and could not found any public source. ... >It worked fine for our purposes >(compressing some boot code into non-volatile memory, and >transferring compressed downloadable images when upgrading >embedded software), but perhaps you'll have better luck >finding a clean port. I would be cautious about incorporating LZW into a current development, due to patent considerations. The following paragraphs are excerpted from ftp://rtfm.mit.edu/pub/usenet/comp.answers/graphics/fileformats-faq/part1: *** ...(much material elided)... "Subject: 1. Is it now illegal to use CompuServe's GIF format? "It is not illegal to own, transmit, or receive GIF files (provided that no unlicensed compression and/or decompression of the files occurs). You must realize, however, that GIF files are not the issue. The issue is, in fact, the LZW data compression algorithm. "In 1984, while working for Sperry Corporation, Terry Welch modified the Lempel-Ziv 78 (LZ78) compression algorithm for greater efficiency for implementation in high-performance disk controllers. The result was the LZW algorithm. The world was informed of the existence of LZW by the following journal article, published by Mr. Welch after he left the employment of Sperry: Welch, T. A., "A Technique for High Performance Data Compression," IEEE Computer, Volume 17, Number 6, June 1984. "In 1985, Sperry Corporation was granted a patent (4,558,302) for the Welch invention and implementation of the LZW data compression algorithm. Since that time, this LZW patent has been publicly available for all to see in the US Patent Office and many public libraries, and is available through many on-line services." ...(balance of FAQ elided)... *** I am sorry to contribute 'FUD' (Fear-Uncertainty-Doubt) here, but the issue of the LWZ patent is widely mentioned. I would _certainly_ seek legal advice before incorporating it into any application where I was unsure of Sperry's patent and license applicability. I'm surprised no one else mentioned this, and would be happy to receive more current and/or authoritative information on the subject. In any case, I would be cautious. Thanks -- john mills -- John M. Mills, Senior Research Engineer -- john.mills@gtri.gatech.edu Georgia Tech Research Institute, Georgia Tech, Atlanta, GA 30332-0834 Phone contacts: 404.894.0151 (voice), 404.894.6258 (FAX) "Lies, Damned Lies, Statistics, and Simulations."