Cell-conditioned multistage vector quantization

Two-stage vector quantization (2VQ) reduces the complexity of single-stage VQ at the cost of reduced performance. Cell-conditioned (CC) 2VQ is proposed to improve the performance of 2VQ, while retaining the advantage of reduced complexity. In CC2VQ, the error vector from the first stage is transformed prior to its quantization by second stage. The effect of transformation is to cause the size and orientation of different first-stage cells to be as similar as possible. It is shown theoretically that CC2VQ performs as well as single-stage VQ under asymptotic conditions. Some experimental results for the vector quantization of speech waveforms are presented to support these theoretical results