On encoding pitch and LPC parameters for low‐rate speech coders

Abstract

This paper describes the development of efficient methods to encode the parameters of long‐term (pitch) and short‐term (LPC all‐pole) prediction filters with a limited bit‐rate, such that the design of high quality speech coders in the 3–4 kbit/s range becomes easier. Our results indicate that good performance can be reached with about 800 bit/s to represent both the pitch lags and the coefficients of a three‐tap pitch filter, thus achieving a significant 36% bit‐rate reduction in comparison with conventional quantization techniques, and using 24 bit/frame to encode spectral parameters relative to a multilanguage speech database.