New algorithm for searching minimum bit rate wavelet representations with application to multiresolution-based perceptual audio coding

Outlines an algorithm for searching minimum bit rate wavelet packet representations in a high quality wavelet-based perceptual audio coder. The algorithm applies wavelet tree and prototype filter adaptation to a perceptual cost function. To achieve such adaptive structure, a periodized wavelet packet transform is performed for each audio frame. After the transform, the encoder employs scalar adaptive quantization, controlled by a psycho-acoustic model in the wavelet domain, followed by entropy coding and bit packing. An adaptive Huffman algorithm that assumes Laplacian distributions for wavelet coefficients is used for entropy coding. A relevant feature of our coder is the method to translate the psycho-acoustic information to the wavelet domain, which allows using orthonormal wavelets of any compact support. Experimental results indicate that our coder ensures `transparent´ coding of monophonic CD audio signals at bit rates lower than 64 kb/s for all the test signals