A STUDY ON ESTIMATING CODING GAIN OF PYRAMID-TYPE NONORTHOGONAL SUBBAND FILTERS

In coding intended for nonreciprocal information compression, it is re quired to attain a high compression rate and minimized error of the re stored signal. The coding gain is the rate of error reduction when the bit error rate is kept constant before and after applying orthonormal transform, such as the discrete cosine transform or orthogonal wavele t transform. This has been used as a quantitative measure of coding pe rformance. On the other hand, the coding gain has been similarly formu lated even in non-orthogonal subband coding such as is used for the de sign of subband filters and for the determination of the optimum distr ibution of quantization error in each subband. In this paper, we point out that an approximation is included in the coding gain estimation e quation for the pyramidal non-orthogonal subband filters used to date. By comparing the estimated coding gains with and without the approxim ation, the coding gain estimation error produced by the approximation is evaluated. For the pyramidal subband filter based on SSKF, the esti mated error of the coding gain produced by the approximation is about 0.1 dB. (C) 1998 Scripta Technica.