Feature extraction and product codes in vector excited coders

A novel approach to code speech signals at low bit rates, while retaining acceptable subjective quality, is presented in this paper. The system falls into the class of vector excited coders, and exploits benefits stemming from the spectral masking effect of the quantizing noise. Since a main disadvantage of conventional vector excited coders is the huge amount of computation associated with the selection of the optimum excitation signal, our primary goal is the development of an efficient and computationalIy simple codebook search method. We present an original scheme based upon a 3-level hierarchical tree vector quantizer.