A combined quantization-interpolation scheme for very low bit rate coding of speech LSP parameters

A combined quantization-interpolation of speech line spectrum pair (LSP) parameters is proposed. To utilize the linear dependency between successive LSP frames, the proposed algorithm attempts to locate the frames where there is a significant spectral change; these frames are encoded by vector quantization. The remaining frames are reconstructed by linear interpolation between the vector-quantized frames. A two-pass algorithm is used to couple the quantization and interpolation operations. Simulation results for the performance of the combined quantization-interpolation approach indicate that, at rates below 350 bits/s (for coding the spectral parameters), the proposed scheme outperforms the multiframe coding scheme of D. P. Kemp et al. (ICASSP-91, p.609-12). The effect of maximum delay on the overall performance is studied, and the performance of the proposed system over noisy channels is examined.<>