A vector ADPCM analysis-by-synthesis configuration for 16 kbit/s speech coding

A speech-coding algorithm based on the introduction of a vector quantizer into an ADPCM (adaptive differential pulse code modulation) configuration is presented. This vector ADPCM (VADPCM) algorithm is directed toward low-complexity, low-delay (0-5 ms), 16-kb/s applications. An analysis-by-synthesis configuration is used to allow the vector quantizer to operate with the usual scalar linear predictor. Performance/complexity tradeoffs are described. Methods for reducing the implementation complexity to the level of the standard 32-kb/s CCITT algorithm are indicated. Noise feedback, postfiltering, and gain-adaptive vector quantization are used to improve the performance while maintaining low complexity.<
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