Principles of Speech Coding

Abstract

Speech coding is the art of reducing the bit rate required to describe a speech signal. In this chapter, we discuss the attributes of speech coders as well as the underlying principles that determine their behavior and their architecture. The ubiquitous class of linear-prediction-based coders is used as an illustration. Speech is generally modeled as a sequence of stationary signal segments, each having unique statistics. Segments are encoded using a two-step procedure: (1) find a model describing the speech segment, (2) encode the segment assuming it is generated by the model. We show that the bit allocation for the model (the predictor parameters) is independent of overall rate and of perception, which is consistent with existing experimental results. The modeling of perception is an important aspect of efficient coding and we discuss how various perceptual distortion measures can be integrated into speech coders.