Optimal quantization of LSP parameters [speech coding]

Two nonuniform aspects of the line spectrum pair (LSP) linear predictive coding parameters are investigated, including nonuniform statistical distributions and spectral sensitivities of adjacent LSP frequency differences. Based on these two nonuniform properties, a novel, globally optimal, scalar quantizer is designed for each differential LSP frequency. The design algorithm is based on dynamic programming, and minimization of a nontrivial data dependent spectral distortion is adopted as the optimality criterion. The LSP quantizer can achieve a 1-dB average log spectral distortion, which is the experimental difference limen (DL) for producing perceptually transparent spectral information at 32 bits/frame. The quantization performance is shown to be fairly robust across different speakers and databases