Including zeros in the backward adaptive predictor of AVPC coders

The inclusion of a pole-zero vector predictor in the backward loop of an AVPC coder[1] is approached . We hope to reach the same profit shown by the pole-zero predictor in the ADPCM-CCITT standard. By using a VLMS transversal algorithm the obtained behaviour does not outperform the all-pole scheme. We argue it is due to the dependence on the eigenvalues spread of the LMS perfomance. By using an orthogonalized-lattice structure this problern can be overcame. The zeros term shows an aditional advantage consisting in the removal of the artificial correlation introduced by the pole term of the predictor. This Ieads to a better profit of the VQ ability and a good coding perfomance of the whole system.