Patent ID: 6799164
Filing Date: 2004-09-28
Classification: G10L

Abstract:
A digital acoustic signal coding apparatus in which a digital acoustic signal is inputted along a time axis and divided into blocks therealong, processes of at least sub-band division or conversion from time to frequency area are practiced per each of the respective blocks said acoustic signal is divided into plural band widths, coded bits are allocated to each of said respective band widths, a normalized coefficient is obtained corresponding to the coded bit number of the allocated bits, and said digital acoustic signal is compressed and coded by quantizing said acoustic signal with said normalized coefficient,wherein, when the conversion to said frequency area is performed, said acoustic signal divided into the blocks is converted to either one of a long conversion block or plural short conversion blocks; wherein, when said short conversion blocks are employed, said plural short conversion blocks are divided into groups of plural blocks respectively including one or plural short conversion blocks; wherein said acoustic signal is quantized by a quantizing medium configured to cause one or plural short conversion blocks included in the same group to correspond to a common normalized coefficient; and wherein said digital acoustic signal coding apparatus comprises: a perceptual entropy calculation medium configured to calculate perceptual entropy of an input acoustic signal per each of said respective short conversion blocks; a perceptual entropy total sum calculation medium configured to obtain a total sum in a frame of said perceptual entropy calculated by said perceptual entropy calculation medium; a comparison medium configured to compare the absolute value of a difference between respective total sums of two frames of perceptual entropy that are successive in relation to the an elapsed time with a previously determined threshold value; and a long/short blocks judgment medium configured to judge whether long block conversion or short blocks conversion should be used to convert a block of said input acoustic signal blocks on the basis of the comparison result obtained by said comparison medium.