Best wavelet-packet bases for audio coding using perceptual and rate-distortion criteria

This paper presents a new approach to the adaptation of a wavelet filterbank based on perceptual and rate-distortion criteria. The system makes use of a wavelet-packet transform where each subband can have an individual time-segmentation. Boundary effects can be avoided by using overlapping blocks of samples and therefore switching bases is possible at every tree-level without affecting other subbands. A modified psychoacoustic model using perceptual entropy can control the switching of the wavelet filterbank and the individual time-segmentation of every subband allows one to take advantage of temporal masking. Additionally a rate-distortion measure can control the filterbank for lossless audio coding applications or in cases where large coding gains can be achieved without using perceptual criteria. The weight of the perceptual measure as well as the weight of the rate-distortion measure can be selected individually, enabling to trade lossless coding versus perceptual coding.