DATA COMPACTION AND DECOMPACTION SYSTEM WITH DIRECT CATALOG UPDATING ALTERNATING WITH STRING SEARCH Russian patent published in 2002 - IPC

FIELD: data compaction and decompaction using catalogs. SUBSTANCE: catalog based data compaction and decompaction system functions as follows: when incomplete string W in compaction device and catalog character C coincide, new string in which character C functions as incomplete string expansion character PW, where P is string corresponding to last compacted-code output signal, is entered in catalog. Update string is entered in compaction catalog for each read-out and coinciding input character. Catalog is directly updated and this procedure is alternating with search for character-by-character coincidence for current string. Update process goes on until greatest-length coincidence is found in catalog. Output of string code of greatest-length coincidence is effected in string coincidence search cycle. If catalog has single character or string A is composed of many characters, then string AAA A is encoded by means of two compacted-code signals irrespective of string length. Such encoding brings unidentified code in signal decompaction device. In response to undefined code signal the update string decompaction device enters update strings in decompaction device catalog, this string being consistent with signal of preceding code obtained, signal of unidentified code, existing code of decompaction device, and number of characters in preceding recovered string. EFFECT: enhanced precision of data transmission. 38 cl, 31 dwg