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BZZ(1)				 DjVuLibre-3.5				BZZ(1)

NAME
       bzz - DjVu general purpose compression utility.

SYNOPSIS
   Encoding:
       bzz -e[blocksize] inputfile outputfile

   Decoding:
       bzz -d inputfile	outputfile

DESCRIPTION
       The first form of the command line (option -e) compresses the data from
       file inputfile and writes the compressed	 data  into  outputfile.   The
       second form of the command line (option -d) decompressed	file inputfile
       and writes the output to	outputfile.

OPTIONS
       -d     Decoding mode.

       -e[blocksize]
	      Encoding mode.  The optional argument  blocksize	specifies  the
	      size  of	the input file blocks processed	by the Burrows-Wheeler
	      transform	expressed in kilobytes.	 The default  block  sizes  is
	      2048  KB.	  The  maximal	block  size  is	4096 KB.  Specifying a
	      larger block size	usually	produces higher	compression ratios and
	      increases	 the  memory  requirements of both the encoder and de-
	      coder.  It is useless to specify a block	size  that  is	larger
	      than the input file.

ALGORITHMS
       The  Burrows-Wheeler  transform is performed using a combination	of the
       Karp-Miller-Rosenberg and the  Bentley-Sedgewick	 algorithms.  This  is
       comparable  to (Sadakane, DCC 98) with a	slightly more flexible ranking
       scheme. Symbols are then	ordered	according to  a	 running  estimate  of
       their  occurrence frequencies.  The symbol ranks	are then coded using a
       simple fixed tree and the ZP binary adaptive coder (Bottou, DCC 98).

       The Burrows-Wheeler transform is	also used in the well known compressor
       bzip2.	The  originality  of  bzz is the use of	the ZP adaptive	coder.
       The adaptation noise can	cost up	to 5 percent in	file  size,  but  this
       penalty is usually offset by the	benefits of adaptation.

PERFORMANCE
       The  following  table shows comparative results (in bits	per character)
       on the Canterbury Corpus	( http://corpus.canterbury.ac.nz ).  The  very
       good bzz	performance on the spreadsheet file excl puts the weighted av-
       erage ahead of much more	sophisticated compressors such as fsmx.

+-------------------------------------------------------------------------------------------------------------+
|					   Compression performance					      |
|	      text   fax    csrc   excl	  sprc	 tech	poem   html   lisp   man    play   Weighted   Average |
+-------------------------------------------------------------------------------------------------------------+
| compress    3.27   0.97   3.56   2.41	  4.21	 3.06	3.38   3.68   3.90   4.43   3.51     2.55      3.31   |
| gzip -9     2.85   0.82   2.24   1.63	  2.67	 2.71	3.23   2.59   2.65   3.31   3.12     2.08      2.53   |
| bzip2	-9    2.27   0.78   2.18   1.01	  2.70	 2.02	2.42   2.48   2.79   3.33   2.53     1.54      2.23   |
| ppmd	      2.31   0.99   2.11   1.08	  2.68	 2.19	2.48   2.38   2.43   3.00   2.53     1.65      2.20   |
| fsmx	      2.10   0.79   1.89   1.48	  2.52	 1.84	2.21   2.24   2.29   2.91   2.35     1.63      2.06   |
| bzz	      2.25   0.76   2.13   0.78	  2.67	 2.00	2.40   2.52   2.60   3.19   2.52     1.44      2.16   |
+-------------------------------------------------------------------------------------------------------------+

       Note that DjVu contributors have	several	entries	in this	 table.	  Pro-
       gram  compress was written some time ago	by Joe Orost.  Program ppmd is
       an improvement of the PPM-C method invented by Paul Howard.

CREDITS
       Program bzz was written by  Leon	 Bottou	 <leonb@users.sourceforge.net>
       and  was	 then  improved	 by Andrei Erofeev <andrew_erofeev@yahoo.com>,
       Bill Riemers <docbill@sourceforge.net> and many others.

SEE ALSO
       djvu(1),	compress(1), gzip(1), bzip2(1)

DjVuLibre-3.5			  10/11/2001				BZZ(1)

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | ALGORITHMS | PERFORMANCE | CREDITS | SEE ALSO

Want to link to this manual page? Use this URL:
<https://www.freebsd.org/cgi/man.cgi?query=bzz&manpath=FreeBSD+12.1-RELEASE+and+Ports>

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