ON THE CODING GAIN OF DYNAMIC HUFFMAN CODING APPLIED TO A WAVELET-BASED PERCEPTUAL AUDIO CODER

Abstract

This paper evaluates the coding gain of using a dynamic Huffman entropy coder in an audio coder that uses a wavelet-packet decomposition that is close to the subband decomposition made by the human ear. The subband audio signals are modeled as samples of a stationary random process with laplacian probability density function because experimental results indicate that the highest coding efficiency is obtained in that case. We have also studied how the entropy coding gain varies with the band index. The proposed adaptive Huffman coding method gives rise to an average coding gain of approximately 0.25 bits per sample compared to binary coding. A further coding gain can be achieved if timevarying filter banks are used. Experimental results tell us that using a suitable method to translate the psychoacoustic information to the wavelet domain, combined with our adaptive Huffman coding scheme, binary rates of about 64 kbps can be obtained for transparent coding of CD quality monophonic audio signals. 1