Comprehensive improvement in low bit rate speech coding

Abstract

A comprehensive improved LPC (linear prediction coding) vocoder scheme is suggested. Many effective techniques are used in the scheme, such as vector quantization (VQ), line-spectrum pair parameters, and the just-noticeable-difference error criterion. By using these techniques it is possible to increase the linear prediction order from 10 to 14, and the sampling rate from 8 to 10 kHz without increasing the transmission bit rate. The design principles and the specifications of the scheme are introduced. Computer simulation shows that it gives very good synthetic speech quality at 2400 b/s. The sonograms of the original and synthesized speeches are also given for comparison.<>