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 Title: |
US4558302:
High speed data compression and decompression apparatus and method
[ Derwent Title ]
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| Country: |
US United States of America
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| Inventor: |
Welch, Terry A.; Concord, MA
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| Assignee: |
Sperry Corporation, New York, NY
other patents from UNISYS CORPORATION (596125) (approx. 6,717)
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| Published / Filed: |
1985-12-10
/ 1983-06-20
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| Application Number: |
US1983000505638
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| IPC Code: |
Advanced:
G06F 5/00;
G06T 9/00;
G11B 20/10;
H03M 7/30;
H03M 7/40;
H03M 7/46;
H04B 14/04;
H04L 23/00;
Core:
more...
IPC-7:
G06F 5/00;
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| U.S. Class: |
Current:
341/051;
341/095;
Original:
340/347.DD;
235/310;
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| Field of Search: |
340/347 DD
235/310,311
364/200,900
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| Priority Number: |
| 1983-06-20 |
US1983000505638 |
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| Abstract: |
A data compressor compresses an input stream of data character signals by storing in a string table strings of data character signals encountered in the input stream. The compressor searches the input stream to determine the longest match to a stored string. Each stored string comprises a prefix string and an extension character where the extension character is the last character in the string and the prefix string comprises all but the extension character. Each string has a code signal associated therewith and a string is stored in the string table by, at least implicitly, storing the code signal for the string, the code signal for the string prefix and the extension character. When the longest match between the input data character stream and the stored strings is determined, the code signal for the longest match is transmitted as the compressed code signal for the encountered string of characters and an extension string is stored in the string table. The prefix of the extended string is the longest match and the extension character of the extended string is the next input data character signal following the longest match. Searching through the string table and entering extended strings therein is effected by a limited search hashing procedure. Decompression is effected by a decompressor that receives the compressed code signals and generates a string table similar to that constructed by the compressor to effect lookup of received code signals so as to recover the data character signals comprising a stored string. The decompressor string table is updated by storing a string having a prefix in accordance with a prior received code signal and an extension character in accordance with the first character of the currently recovered string.
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| Attorney, Agent or Firm: |
Terry, Howard P. ;
Cooper, Albert B. ;
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| Primary / Asst. Examiners: |
Miller, Charles D.;
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| Maintenance Status: |
CC Certificate of Correction issued
B1 Re-examined
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| INPADOC Legal Status: |
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| Designated Country: |
DE FR GB IT
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| Family: |
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First Claim:
Show all 181 claims |
I claim:
1. In a data compression and data decompression system, compression apparatus for compressing a stream of data character signals into a compressed stream of code signals, said compression apparatus comprising
- storage means for storing strings of data character signals encountered in said stream of data character signals, said stored strings having code signals associated therewith, respectively,
- means for searching said stream of data character signals by comparing said stream to said stored strings to determine the longest match therewith,
- means for inserting into said storage means, for storage therein, an extended string comprising said longest match with said stream of data character signals extended by the next data character signal following said longest match,
- means for assigning a code signal corresponding to said stored extended string, and
- means for providing the code signal associated with said longest match so as to provide said compressed stream of code signals.
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| Background / Summary: |
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| Drawing Descriptions: |
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| Description: |
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| Forward References: |
Show 236 U.S. patent(s) that reference this one
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