An improved modulo-PCM speech encoder with an imbedded vector quantizer

The Modulo-PCM (MPCM) coder works very well at medium and high bit rates, but its performance is poor at 16 kbs or less. The reason for this is the poor quantization of the fractional part and the resulting noise accumulation in the prediction loop at the decoder. In this paper, we suggest a remedy to this problem by imbedding a vector quantizer. Our scheme is simple and efficient.