Application of a VLSI Vector Quantization Processor to Real-Time Speech Coding

The major obstacle which has limited the use of Vector Quantization (VQ) for real-time speech coding is the computationally demanding codebook-search algorithm. The essential task of this algorithm, pattern matching, has several properties which make it amenable to VLSI realization using a highly concurrent processor architecture. A VLSI pattern-matching chip provides the essential building-block for a specialpurpose codebook-search processor (CSP). The CSP can serve as a generic architecture for a variety of VQ-based speech coding applications. This paper reports on a working VQ processor for speech coding based on a first generation VLSI chip that efficiently performs the essential pattern-matching operation needed for the codebook-search process. Furthermore, the CSP architecture, using this chip, has been successfully incorporated into a compact single-board Vector PCM implementation which operates at rates between 7 and 18 kbits/s. A real-time Adaptive Vector Predictive Coder system using the CSP and augmented by a TMS-32010 programmable signal processor has been designed and recently implemented. We describe the structure of these two VQ coders and present experimental results obtained using the single-board Vector PCM coder.