  In this paper we propose a Non-Linear Predictive Vector quantizer (PVQ) for
speech coding, based on Multi-Layer Perceptrons. We also propose a method to
evaluate if a quantizer is well designed, and if it exploits the correlation
between consecutive outputs. Although the results of the Non-linear PVQ do not
improve the results of the non-linear scalar predictor, we check that there is
some room for the PVQ improvement.
