1. <
application> (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,
run-length encoding replaces strings of repeated characters
(or other units of data) with a single character and a count.
There are many
compression algorithms and utilities.
Compressed data must be decompressed before it can be used.
The standard
Unix compression utilty is called
compress
though
GNU's superior
gzip has largely replaced it. Other
compression utilties include
pack,
zip and
PKZIP.
When compressing several similar files, it is usually better
to join the files together into an
archive of some kind
(using
tar for example) and then
compress them, rather than
to join together individually compressed files. This is
because some common
compression 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
TIFF,
JPEG,
MPEG,
Lempel-Ziv Welch,
"
lossy", "
lossless".
{
compression-faq/">Compression FAQ
(ftp://rtfm.mit.edu/pub/usenet/news.answers/compression-faq/)}.
{
compression/compression.html">Web Content Compression FAQ
(http://perl.apache.org/docs/tutorials/client/compression/compression.html)}.
Usenet newsgroups:
news:comp.compression,
news:comp.compression.research.
2. <
multimedia> 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)