Method and apparatus using multi-path multi-stage vector quantizer

In a multistage, multipath, split vector quantizer, the quantizer including a plurality of split vector quantization codebook stages, each split vector quantization codebook stage having at least two sub-codebooks, there being one sub-codebook for each split of a given split vector quantization codebook stage, wherein a set of best candidate codevectors is selected for each split and from each split vector quantization codebook stage;

• and a trellis-coded, multipath, backward tracking mechanism for selecting a final codevector from the sets of best candidate codevectors, a method of training codevectors for each sub-codebook of each split vector quantization codebook stage, the method comprising the steps of:
• obtaining an initial set of sub-codebooks, there being at least two sub-codebooks available in each split vector quantization codebook stage;
• training one sub-codebook while fixing the remaining sub-codebooks of the initial set of sub-codebooks;
• comparing an input training vector for the one sub-codebook with a final codevector to derive a distortion measure;
• forming a partition for each current sub-codebook entry of the sub-codebook being trained, the partition comprising a set of training data that minimizes the distortion measure for the sub-codebook entry;
• updating each partition with a centroid partition;
• and
• performing the training, comparing, forming, and updating steps for each sub-codebook to achieve an overall distortion measure.