| |||||||||||||
|
| |||||||||||||
LZW and gzipLZW and gzipPosted Jun 16, 2003 20:31 UTC (Mon) by roelofs (subscriber, #2599)Parent article: LZW is Free! (Almost) For example, LZW is used in the Unix "compress" utility, which led to the creation of the widely-used gzip as a replacement. "Led to" principally in the sense that any inferior technology leads to the creation of better technologies. gzip ultimately owes its development to PKWARE in the sense that they replaced LZW ("shrinking") with some Shannon-Fano thing ("implosion") in PKZIP 1.1 and then with an LZ77 derivative ("deflation") sometime around March 1991, IIRC (whenever PKZIP 1.93a came out). PKZIP's documentation of the format in appnote.txt opened the door for Info-ZIP's free implementations of inflate() and deflate(), and those in turn became the basis for gzip (and later zlib). Whether the LZW patent had anything to do with PKWARE's switch, I don't know. But I do know that they had at least four compression methods in use by that time, not counting whatever was used in PKARC/PKPAK, and all of this happened long before Unisys started asserting its patent. That said, Jean-loup was paying attention to patents by then, but they were mostly those related to deflation, such as one by Fiala and Green[e]. Btw, in response to another poster, Unisys was the merger of Sperry-Rand and Burroughs, as I recall ("the power of 2" or something). The Sperry half brought the LZW patent. Greg Roelofs
(Log in to post comments)
|
|
||||||||||||