A METHOD FOR ESTIMATING CODING GAIN OF AN ORTHOGONAL WAVELET TRANSFORM CONSIDERING HIGHER-ORDER STATISTICS

In applications such as subband coding, the coding gain is a useful ev aluation measure for representing the bit-rate reduction performance o f the subband filter for the object of coding. It is widely used in th e estimation of coding performance and the design of subband filters. To estimate the coding gain requires knowledge of the probability dens ity distribution of the object of coding and the decomposed subband se ries. Identification of the probability density function, however, is in general difficult. Consequently an approximation is often used in t he estimation of the coding gain, where it is assumed that the probabi lity density distributions of the object of coding and all subband ser ies are the same. Thus, estimation of the coding gain contains an erro r for data, such as images, where this assumption is not satisfied. Th is paper notes that the probability density distribution of the subban d decomposed image can be well approximated by a generalized Gaussian distribution and proposes a method for a more accurate estimation of t he coding gain in the orthogonal wavelet transform attained by a varie ty of subband filter, using the higher-order statistics of the object of coding. The coding gain is estimated for several objects of coding. Comparing the result to the actually measured value, it is shown that the accuracy of estimation is greatly improved in the proposed method , compared to the method based on an approximation. (C) 1998 Scripta T echnica.