Efficient coding of speech spectral envelope using a non-linear two-dimensional predictive method in the index domain

Line spectral frequencies (LSFs) are the most popular parameters for spectrum quantization in speech coders using linear prediction. A new method for the quantization of the LSFs is proposed in this paper. This method is a scalar quantization scheme based on a nonlinear two-dimensional prediction in the index domain, and hereafter will be referred to as predictive delta adaptive scalar quantization (PDASQ). It is shown that it can be implemented efficiently with negligible computational overhead and memory requirements compared to the simple scalar quantization method. Although PDASQ needs lower bit rates, its quantization distortion is of the same order as that of the conventional scalar quantization. Satisfactory performance of the new method is verified through experimental tests using computer simulation