A New Deterministic Codebook Structure for CELP Speech Coding

Low bit rate, high quality speech coding is a vital part in voice telecommunication systems. The introduction of CELP (1984) (Codebook Excited Linear Prediction) speech coding provided a feasible way to compress speech data to 4.8 kbps with high quality, but the formidable computational complexity required for real-time processing has prevented its wide application. Using the new deterministic codebook, we reduce the computational complexity of codebook search, which originally accounted for 2/3 of the computational complexity, to negligible. Based on this reduction, we produce an algorithm with complexity about 5 MIPS. It can be implemented in even inexpensive DSP chips, while maintaining the same high quality. In addition to extremely simple encoding and decoding schemes, this codebook also provides optimal error tolerance and it doesn't require codebook storage. We hope that this contribution can finally make CELP speech coding a widely applicable and practical technology.