1BZZ(1) DjVuLibre-3.5 BZZ(1)
2
6 bzz - DjVu general purpose compression utility.
7
10 Encoding:
11 bzz -e[blocksize] inputfile outputfile
12 Decoding:
14 bzz -d inputfile outputfile
15
17 The first form of the command line (option -e ) compresses the data
18 from file inputfile and writes the compressed data into outputfile.
19 The second form of the command line (option -d ) decompressed file
20 inputfile and writes the output to outputfile.
21
24 -d Decoding mode.
25 -e[blocksize]
27 Encoding mode. The optional argument blocksize specifies the
28 size of the input file blocks processed by the Burrows-Wheeler
29 transform expressed in kilobytes. The default block sizes is
30 2048 KB. The maximal block size is 4096 KB. Specifying a
31 larger block size usually produces higher compression ratios and
32 increases the memory requirements of both the encoder and
33 decoder. It is useless to specify a block size that is larger
34 than the input file.
35
38 The Burrows-Wheeler transform is performed using a combination of the
39 Karp-Miller-Rosenberg and the Bentley-Sedgewick algorithms. This is
40 comparable to (Sadakane, DCC 98) with a slightly more flexible ranking
41 scheme. Symbols are then ordered according to a running estimate of
42 their occurrence frequencies. The symbol ranks are then coded using a
43 simple fixed tree and the ZP binary adaptive coder (Bottou, DCC 98).
44 The Burrows-Wheeler transform is also used in the well known compressor
46 bzip2. The originality of bzz is the use of the ZP adaptive coder.
47 The adaptation noise can cost up to 5 percent in file size, but this
48 penalty is usually offset by the benefits of adaptation.
49
52 The following table shows comparative results (in bits per character)
53 on the Canterbury Corpus ( http://corpus.canterbury.ac.nz ). The very
54 good bzz performance on the spreadsheet file excl puts the weighted
55 average ahead of much more sophisticated compressors such as fsmx.
56┌─────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
59│ Compression performance │
60│ text fax csrc excl sprc tech poem html lisp man play Weighted Average │
61├─────────────────────────────────────────────────────────────────────────────────────────────────────────────┤
62│ 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 │
63│ 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 │
64│ 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 │
65│ 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 │
66│ 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 │
67│ 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 │
68└─────────────────────────────────────────────────────────────────────────────────────────────────────────────┘
69 Note that DjVu contributors have several entries in this table. Pro‐
71 gram compress was written some time ago by Joe Orost. Program ppmd is
72 an improvement of the PPM-C method invented by Paul Howard.
73
76 Program bzz was written by Léon Bottou <leonb@users.sourceforge.net>
77 and was then improved by Andrei Erofeev <andrew_erofeev@yahoo.com>,
78 Bill Riemers <docbill@sourceforge.net> and many others.
79
82 djvu(1), compress(1), gzip(1), bzip2(1)
83DjVuLibre-3.5 10/11/2001 BZZ(1)