Provided by: djvulibre-bin_184.108.40.206-5_amd64
bzz - DjVu general purpose compression utility.
Encoding: bzz -e[blocksize] inputfile outputfile Decoding: bzz -d inputfile outputfile
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.
-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 decoder. It is useless to specify a block size that is larger than the input file.
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.
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 average ahead of much more sophisticated compressors such as fsmx. ┌─────────────────────────────────────────────────────────────────────────────────────────────────────────────┐ ├─────────────────────────────────────────────────────────────────────────────────────────────────────────────┤ │ 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. Program compress was written some time ago by Joe Orost. Program ppmd is an improvement of the PPM-C method invented by Paul Howard.
Program bzz was written by Léon Bottou <firstname.lastname@example.org> and was then improved by Andrei Erofeev <email@example.com>, Bill Riemers <firstname.lastname@example.org> and many others.