Entropy-constrained spike modulus quantization in a bio-inspired universal audio coder

We propose an optimal quantizer for the moduli (spike am-plitudes) of the matching pursuit on gammatone/gammachirp kernels that have been shown previously to be very efficient for audio coding. The quantizer optimization is performed by Genetic Algorithm (GA). We show that the optimal quanti-zation values found by GA can be approximated by a ”piece-wise uniform ” quantizer. The latter approximation is faster and has less overhead (i.e., there is no need for codebook transmission). Based on perceptual evaluation of audio qual-ity, transparent quality is obtained for both the optimal and piecewise uniform quantization approaches. We also stud-ied the performance of in-loop quantization vs. out-of-loop quantization when computational cost can be afforded. 1