Patent ID: 6661839
Filing Date: 2003-12-09
Classification: G01R,H03M

Abstract:
A data compressing and expanding method for compressing an inputted data to a compressed data and for expanding the compressed data to an expanded data, wherein the inputted data has a uniform data type and is composed of a plurality of unit data sequences and the respective unit data sequences are different at least either in their data structures or statistical characteristics of data, said method including the steps of:counting a number of data changes of each said divided unit data sequence as a factor of difference in the data structure; measuring an appearing probability of each symbol in each said divided unit data sequence and calculating an entropy of the data as a factor of difference in the statistical characteristics of data based on measured result of the appearing probabilities of the symbols; comparing the number of data changes with a threshold value of the number of data changes and also comparing the entropy of the data with the threshold value of entropy; dividing the inputted data to the respective unit data sequences and distributing the respective divided unit data sequences in accordance with the comparison results to a plurality of compressing blocks; compressing the respective divided unit data sequences distributed to said plurality of compressing blocks using different compressing methods which are each suitable for each block to thereby obtain a compressed data; dividing the compressed data to respective compressed unit data sequences and distributing the thus divided respective compressed unit data sequences in accordance with their compressing methods used to a plurality of expanding blocks in accordance with difference in the compressing methods used; and expanding the respective compressed unit data sequences contained in each of said plurality of the expanding blocks by using a suitable one expanding method which is selected for each said expanding block from different expanding methods so as to correspond to the compressing method used to the compressed unit data sequence.