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1994-03-06
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SQSH
A LZ based cruncher with special algorithms for 8 bit sample data
Version 1.10
Copyright 1994 by John Hendrikx
License/Disclaimer
------------------
This library may be freely distributed, as long as it is kept in its
original, complete, and unmodified form. It may not be distributed in a
commercial package of any kind without my permission.
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE.
Installation
------------
You'll need to install the XPK package first to use this library. The
XPK package should be available on most Bulletin Board Systems, so try to
get it there.
If you already have the XPK package installed, then to add this library
to your system simply copy the xpkSQSH.library from the 68000 or 68020
subdirectory to your LIBS:Compressors/ dir.
Description
-----------
SQSH is an XPK packer sublibrary which implements an optimized LZ based
algorithm combined with a 8 bit delta compression algorithm.
This packer was especially made for packing 8 bit Samples and ProTracker
style modules. It's NOT a lossy compression library, so NO quality-loss
will occur when packing Samples with this library.
SQSH is pretty fast at decompression (300K/s on A3000) so is very well
suited to compress Modules and Samples since these will typically be packed
once and unpacked many times. It's slow at compression (25K/s on A3000)
mainly because every part of the file has to be checked twice to see what
the better compression method would be.
In order to achieve reasonable compression of other types of files
(Executables, Textfiles) this packer will scan a long range (about 20K) for
identical byte sequences and if it finds any, it outputs offset and length
instead of the bytes themselves. Scanning such a long range for duplicates
is a CPU-intensive process. I have tried to make it as fast as possible
(about 25K/s on A3000) but NUKE proves it can be done faster :-)
In the archive also is included a 68000 version of this library. Sorry
all you 68000 users for the long delay, but I only received one message
asking me for a 68000 version. It was Edmund Vermeulen who eventually
convinced me to program the 68000 version.
Statistics
----------
As I don't own a A3000 and xBench, I cannot give results which you can
compare with the other XPK libraries. But I can offer you some results I
got on my own machine (that is a A2000 with a 22Mhz 68030 GVP with 6 Mb of
60ns 32bit ram)
Frequency Original SQSH = Squash LhA
------------------------------------------------------------
Sample 15 KHz 732984 418144 (43.0%) 510377 (30.4%)
Sample 20 KHz 979990 532512 (45.7%) 664365 (32.2%)
Sample 25 KHz 1219832 634488 (48.0%) 805746 (33.9%)
Sample 30 KHz 1465864 728656 (50.3%) 940955 (35.8%)
Sample 35 KHz 1710140 815652 (52.3%) 1066660 (37.6%)
Sample 40 KHz 1959924 898416 (54.2%) 1186449 (39.5%)
Sample 45 KHz 2208002 976340 (55.8%) 1294084 (41.4%)
Sample 50 KHz 2456810 1048384 (57.3%) 1389138 (43.5%)
Sample 55 KHz 2725502 1144420 (58.0%) 1506860 (44.7%)
--------------------------------------------------------------------------
| ** SQUASH ** | ** LHA **
FileName Original | % Pack Unpack | % Pack Unpack
(in bytes) | K/s K/s | K/s K/s
--------------------------------------------------------------------------
Intuition (AutoDoc) 283460 | 60.9% 18.7 369.1 | 66.7% 31.9 247.2
MUI.guide 80052 | 58.7% 22.9 312.7 | 65.0% 26.3 211.3
AmigaVision 594712 | 42.4% 22.1 276.6 | 48.7% 18.4 206.7
VirusChecker 42380 | 30.2% 26.0 197.1 | 38.0% 20.8 153.3
Mod.February symph 240420 | 27.8% 29.7 335.4 | 24.2% 25.0 166.5
Mod.Infinite finit 180950 | 41.6% 28.5 353.4 | 38.7% 20.7 182.2
Mod.Began in Africa 197038 | 41.5% 31.2 356.3 | 37.1% 21.6 194.3
Mod.Poing 94530 | 35.1% 15.7 329.7 | 33.8% 27.2 171.0
Mod.Resonance 2 188354 | 43.5% 29.2 375.4 | 35.9% 21.9 182.1
Mod.Tranze seven 215872 | 43.5% 28.5 351.4 | 36.3% 22.4 189.1
OnlyWithYou.8SVX 1219832 | 48.0% 30.2 385.5 | 33.9% 29.4 180.2
--------------------------------------------------------------------------
Contact Address
---------------
FIDO: 2:285/813.8 SNAIL: John Hendrikx
AMY: 39:153/201.8 Figarostraat 36
NLA: 14:101/200.8 3208 PD Spijkenisse
The Netherlands