Patent ID: 6778103
Filing Date: 2004-08-17
Classification: H03M

Abstract:
A data compressing apparatus having an input buffer for holding a string of data to be compressed, said input buffer comprising a Lempel buffer for storing an already compressed portion and a Ziv buffer for storing a portion to be compressed, comprising:an occurrence position holding unit holding a part of all of an occurrence position of an n-character string (n&gE;1) in the Lempel buffer; an occurrence/non-occurrence check unit checking whether or not said occurrence position holding unit holds an occurrence position of a character string matching the n-character string immediately before the Ziv buffer; an occurrence position obtaining unit obtaining the occurrence position of the character string matching the n-character string immediately before the Ziv buffer when the occurrence position is held by said occurrence position holding unit; a matching length detection unit detecting a matching length between a character string after the occurrence position and a character string after a start of the Ziv buffer; a matching length coding unit coding a portion matching the character string after the occurrence position based on the matching length when said occurrence/non-occurrence check unit confirms that the occurrence position of the n-character string immediately before the Ziv buffer is held; an intermediate buffer for holding a matching portion after an occurrence position of a character string matching the n-character string in the lempel buffer, with the matching portion replaced with a code indicating the matching length, and with the other portions held as data to be compressed as is; a character-with-context code holding unit holding a code of a next occurring character using an immediately previous 0 through (mâˆ’1) character string as a context; a character-with-context retrieval unit retrieving a subsequent character from said character-with-context code holding unit using an immediately previous 0 through (mâˆ’1) character string as a context; and a character-with-context coding unit coding a character-with-context retrieved by said character-with-context retrieval unit according to a code held by said character-with-context code holding unit.