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Lexikon

compression

1. (Or "compaction") The coding of data to save storage space or transmission time. Although data is already coded in digital form for computer processing, it can often be coded more efficiently (using fewer bits). For example, ef="module.php?name=Lexikon&file=search&eid=1&query=run-length encoding">run-length encoding replaces strings of repeated characters (or other units of data) with a single character and a count. There are many compression ef="module.php?name=Lexikon&file=search&eid=1&query=algorithms">algorithms and utilities. Compressed data must be decompressed before it can be used. The standard ef="module.php?name=Lexikon&file=search&eid=1&query=Unix">Unix compression utilty is called ef="module.php?name=Lexikon&file=search&eid=1&query=compress">compress though ef="module.php?name=Lexikon&file=search&eid=1&query=GNU">GNU' s superior ef="module.php?name=Lexikon&file=search&eid=1&query=gzip">gzip has largely replaced it. Other compression utilties include ef="module.php?name=Lexikon&file=search&eid=1&query=pack">pack, ef="module.php?name=Lexikon&file=search&eid=1&query=zip">zip and ef="module.php?name=Lexikon&file=search&eid=1&query=PKZIP">PKZIP. When compressing several similar files, it is usually better to join the files together into an ef="module.php?name=Lexikon&file=search&eid=1&query=archive">archive of some kind (using ef="module.php?name=Lexikon&file=search&eid=1&query=tar">tar for example) and then compress them, rather than to join together individually compressed files. This is because some common compression ef="module.php?name=Lexikon&file=search&eid=1&query=algorithm">algorithms build up tables based on the data from their current input which they have already compressed. They then use this table to compress subsequent data more efficiently. See also ef="module.php?name=Lexikon&file=search&eid=1&query=TIFF">TIFF, ef="module.php?name=Lexikon&file=search&eid=1&query=JPeG">JPeG, ef="module.php?name=Lexikon&file=search&eid=1&query=MPeG">MPeG, ef="module.php?name=Lexikon&file=search&eid=1&query=Lempel-Ziv Welch">Lempel-Ziv Welch, "ef="module.php?name=Lexikon&file=search&eid=1&query=lossy">lossy", "ef="module.php?name=Lexikon&file=search&eid=1&query=lossless">lossless". {Compression FAQ (ftp://rtfm.mit.edu/pub/usenet/news.answers/compression-faq/)}. {Web Inhalt Compression FAQ (http://perl.apache.org/docs/tutorials/client/compression/compression.html)}. ef="module.php?name=Lexikon&file=search&eid=1&query=Usenet">Usenet newsgroups: ef="module.php?name=Lexikon&file=search&eid=1&query=news:comp.compression">news:comp.compression, ef="module.php?name=Lexikon&file=search&eid=1&query=news:comp.compression.research">news:comp.compression.research. 2. edia> Reducing the dynamic range of an audio signal, making quiet sounds louder and loud sounds quieter. Thus, when discussing digital audio, the preferred term for reducing the total amount of data is "compaction". Some advocate this term in all contexts. (2004-04-26)

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