Path: utzoo!utgpu!water!watmath!clyde!rutgers!mit-eddie!husc6!bbn!uwmcsd1!csd4.milw.wisc.edu!devilbis
From: devilbis@csd4.milw.wisc.edu (Vilbiss Warren C De)
Newsgroups: comp.sys.amiga
Subject: Re: zoo enhancements solicited
Summary: But PKAX is here now too!
Keywords: arc zoo compression fast! Katz
Message-ID: <4341@uwmcsd1.UUCP>
Date: 24 Jan 88 01:21:15 GMT
References: <2562@gryphon.CTS.COM> <607X@esunix.UUCP>
Sender: daemon@uwmcsd1.UUCP
Reply-To: devilbis@csd4.milw.wisc.edu (Vilbiss Warren C De)
Organization: University of Wisconsin-Milwaukee
Lines: 33

Just a note in regards to the differences between ARC and ZOO compression,
as well as the new PKAX ARC extractor for the Amiga...  First of all, the reason
that ZOO does better on some files, while it does MUCH poorer on others (i.e.,
no compression at all!) is because ZOO only uses Ziv-Lempel 13-bit compression,
while the ARC programs will dynamically choose between 8 different compression 
algorythms.  Well, I should be fair, ZOO *does* have two alternatives; 13 bit
"crunch", or nothing at all!  For some reason, IFF pictures & sound files seem
to ARC more efficiently if they're Squeezed (Huffman compression), which is why ARC wins this one over ZOO.  But, the real answer to the question lies in the
newly-released PKAX ARC extractor for the Amiga, offered by none other than Phil
Katz hisself, of IBM PC fame (and, if I may add, a close personal friend of
mine...).  Anyways, the PKAX program is the extract-only part of the package,
analogous to PKXARC for the PC; he is currently preparing to port the other
half of his PC offering to the Amiga, depending on the fate of PKAX as regards
to "shareware" receipts (actually, in his case, it's more like User Supported 
Software than "shareware", since he had to pay someone to complete the Amiga 
port, and wants to recoup his investment like any other businessperson).

Anyways again, besides being another ARC extraction utility, this program is 
FAST!, which, of course, is one of Phil's trademarks in the PC arena.  Also,
the program is relatively small in size, 18652 bytes long, AND (the finale I've
been leading up to for the last dozen lines or so), it supports Squashing, 
which is the ARC extension that Phil implemented for PKXARC/PC, which is the 
same Ziv-Lempel varient that ZOO uses to get better compression.  Except, in
PKARC/PKXARC/PKAX's case, it's even better, because those programs are able
to more intelligently determine which varient to use on compression to save more
space.  As an example, for a PC, PKARC will make files smaller than ARC will, 
even when Crunching or Squeezing is being used, because the algorithm is more
intelligent.  And, the files can still be unARC'ed by either program (except
for Squashing, which is PK-exclusive for now.)

Well, that's enough for now from me.

  - Mike Shawaluk