Subband coding of prediction error images using constrained-storage VQ
Christoph Stiller, Olaf Hirsch · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 1993
A subband coding scheme for the prediction error in a hybrid coder at a rate of 8 kbit/s is presented. In order to achieve small adress overhead we propose intraband encoding of rectangular shaped regions. An iterative procedure of relaxation type which jointly considers all subbands determines number, size and position oi update rectangles. It is driven by optimization of the coding-gain per bit ratio. The prediction error amplitudes within the selected rectangles compose vectors of different dimensions. They are quantized by a multi codebook vector quantizer which contains one codebook per vector dimension. The problem of large storage requirement of multi codebook vector quantizers is circumvented by a codebook sharing approach. A training procedure for the constrained-storage VQ is presented. In terms of SNR it performs less than 0.5 dB worse than a common multi codebook VQ while saving 90% storage.