Delta coding of LPC parameters

This paper presents an improvement in the quality of the LPC-coded speech at low bit rates (2400 bits/second and below), achieved by reducing the "warbliness" of the steady-state portions of the speech signal. This reduction is made possible by increasing the fineness of quantization of the LPC parameters without increasing the bit rate. The technique used is to transmit the frame-to-frame differences of the encoded parameters whenever the parameters have not changed significantly from one frame to the next.