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compression

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compression


  3  definitions  found 
 
  From  Webster's  Revised  Unabridged  Dictionary  (1913)  [web1913]: 
 
  Compression  \Com*pres"sion\,  n.  [L.  compressio:  cf  F. 
  compression.] 
  The  act  of  compressing,  or  state  of  being  compressed. 
  ``Compression  of  thought.''  --Johnson. 
 
  From  WordNet  r  1.6  [wn]: 
 
  compression 
  n  1:  an  increase  in  the  density  of  something  [syn:  {compaction}, 
  {concretion},  {densification}] 
  2:  the  process  or  result  of  becoming  smaller  or  pressed 
  together:  "the  contraction  of  a  gas  on  cooling"  [syn:  {condensation}, 
  {contraction}] 
  3:  encoding  information  while  reducing  the  bandwidth  or  bits 
  required  [ant:  {decompression}] 
  4:  applying  pressure  [syn:  {compressing}]  [ant:  {decompression}] 
 
  From  The  Free  On-line  Dictionary  of  Computing  (13  Mar  01)  [foldoc]: 
 
  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, 
  {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  {algorithm}s  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 
  (ftp://rtfm.mit.edu/pub/usenet/news.answers/compression-faq/)}. 
 
  {Usenet}  newsgroups:  {news:comp.compression}, 
  {news:comp.compression.research}. 
 
  2.    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. 
 
  (2001-01-30) 
 
 




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