Patent ID: 6061398
Filing Date: 2000-05-09
Classification: G06T,H03M

Abstract:
A data compression apparatus comprising:storage means for storing contexts and code trees according to a Huffman code rule, each of the code trees is related to a context;input means for inputting a character string to be compressed;character obtaining means for obtaining a character to be encoded from the inputted character string;context specifying means for specifying a context occurred just preceding to the character obtained by said character obtaining means;code outputting means for outputting a code corresponding to the character obtained by said character obtaining means in the code tree with respect to the context specified by said context specifying means;updating means for updating the code tree used by said code outputting means in accordance with the Huffman code rule,whereineach of the code trees contains a special code `escape` which is transmitted to signal a decoder to shorten the context,if the data relative to the character obtained by said character obtaining means does not exist in the code tree stored in said storage means with respect to the context specified by said context specifying means, said code outputting means outputs the special code `escape` within the code tree and repeats the outputting of the special code `escape` while shortening the context until the code for the character related to the context is found, and outputs the code of the character; andadding means for adding data about unregistered combinations of character and contexts to said storage means when said code outputting means outputs the special code `escape`.