Optimal wavelet packets for low-delay audio coding

We address the issue of choosing an optimal wavelet packets decomposition for low-delay audio bit-rate reduction. The decomposition tree and the choice of the wavelet filters for each 2-band cell of the tree are optimized. For a given filterbank we measure the entropy of the symbols resulting from a quantization stage ensuring transparent compression. This measure is the criterion to be minimized under a delay constraint. The optimization is carried out with simulated annealing techniques among a large family of filters. We show that there is no loss choosing the wavelet filters among a family of filters that have been optimized with respect to coding gain for AR(1) models. This provides efficient wavelet packets for low bit-rate low delay audio compression