Patent ID: 6697529
Filing Date: 2004-02-24
Classification: H04N

Abstract:
A data compression method comprising:a quantization trial step in which input data is quantized using an initial quantization table set in advance; a coding trial step in which a code volume achieved when the data that has undergone quantization in the quantization trial step is coded is determined; a relationship ascertaining step in which a scale factor in the initial quantization table and the code volume are substituted in a relational expression representing a relationship between a code volume and a scale factor containing two undetermined parameters a and b and the undetermined parameters in the relational expression are ascertained based upon the relational expression after substitution and a statistical relationship between the undetermined parameters a and b determined through a previous quantization operation; a scale factor determining step in which a target scale factor corresponding to a target code volume is determined by using the relational expression having the undetermined parameters ascertained in the relationship ascertaining step substituted therein; a quantization step in which the input data is quantized by using a quantization table corresponding to the target scale factor determined in the scale factor determining step; and a coding step in which the data that has undergone quantization in the quantization step is coded, wherein the relationship ascertaining step further includes: (1) an area selection step in which, with a statistical relationship between the two undetermined parameters a and b ascertained in advance for each of a plurality of areas achieved by dividing a coordinate space whose axes are a scale factor and a code volume, one of the plurality of areas is selected based upon the scale factor in the initial quantization table and the code volume obtained in the coding trial step; and (2) an individual area relationship ascertaining step in which the scale factor in the initial quantization table and the code volume obtained in the coding trial step are substituted in the relational expression and the undetermined parameters in the relational expression are ascertained based upon the relational expression after substitution and the statistical relationship in the area selected in the area selection step.