RedLZSS | SuperCollider 3.13.0 Help

Description

See http://michael.dipperstein.com/lzss/ and http://en.wikipedia.org/wiki/Lempel-Ziv-Storer-Szymanski

A dictionary look-up compressor that performs best with long repeating patterns e.g. [0, 1, 2, 3, 0, 1, 2, 3, 0, 1, 2, 3, 0, 1, 2, 3, 0, 1, 2, 3, 0, 1, 2, 3].

NOTE: Only works with 8bit Integer (0-255) values.

Class Methods

.compress

Expects an array of 8bit integers. Returns a string of binary numbers.

.decompress

Expects a string of binary numbers. Returns an array of 8bit integers.

.binaryStringToBytes

Converts a binary string into 8-bit bytes. Up to 7 zeros might be padded automatically at the end. The number of zeros is stored in *pad. *pad is semi-private and used when converting back to bytes.

.bytesToBinaryString

Converts an array of 8-bit bytes into a binary string.

.pad

Semi-private counter for number of padded zeros. Set by *binaryStringToBytes and read by *bytesToBinaryString.

.window

Maximum sliding window size. The default is 4096.

.length

Maximum length for matching pattern. The default is 32.

Examples

a= [0, 1, 2, 3, 0, 1, 2, 3, 0, 1, 2, 3, 0, 1, 2, 3, 0, 1, 2, 3, 0, 1, 2, 3];
b= RedLZSS.compress(a);
RedLZSS.binaryStringToBytes(b).size/a.size;  //compressed to 29%
c= RedLZSS.decompress(b);
a==c

a= "AABCBBABC".ascii;
b= RedLZSS.compress(a);
c= RedLZSS.decompress(b);
c.collect{|x| x.asAscii}.join;
a==c

a= "abracadabra".ascii;
b= RedLZSS.compress(a);
c= RedLZSS.decompress(b);
a==c

a= "JOEYNJOEYNJOEYJOEYNJOEYNJOEYJOEYNJOEYNJOEYJOEYNJOEYNJOEY".ascii;
b= RedLZSS.compress(a);
c= RedLZSS.binaryStringToBytes(b);
c.size/a.size;  //compressed to 27%
d= RedLZSS.bytesToBinaryString(c);
e= RedLZSS.decompress(d);
e.collect{|x| x.asAscii}.join;
a==e

a= "Man is distinguished, not only by his reason, but by this singular passion from other animals, which is a lust of the mind, that by a perseverance of delight in the continued and indefatigable generation of knowledge, exceeds the short vehemence of any carnal pleasure.".ascii;
b= RedLZSS.compress(a);
RedLZSS.binaryStringToBytes(b).size/a.size;  //compressed to 99%
c= RedLZSS.decompress(b);
c.collect{|x| x.asAscii}.join;
a==c

a= {|i| [0, 0, 0, 1].choose}.dup(5000);
RedLZSS.window= 512;  //decrease window and length to speed up compression
RedLZSS.length= 16;
b= RedLZSS.compress(a);  //very slow to compress large arrays
RedLZSS.binaryStringToBytes(b).size/a.size;  //compressed to around 22% (also 22% with default window and length values)
c= RedLZSS.decompress(b);  //fast to decompress
a==c

helpfile source: HelpSource/Classes/RedLZSS.schelp
link::redSys/Classes/RedLZSS::

RedLZSSExtension