Adaptive Linear Prediction in Speech Coding

Adaptive linear prediction is commonly used as a key step in digital coding of speech. This paper discusses some of the techniques that have been developed for adapting and coding the predictor coefficients in speech coders. The linear predictors in high quality speech coding often consist of two stages, a short-time span (formant) filter and a long-time span (pitch) filter. The use of such filters in analysis-by-synthesis coders is examined. In addition, backward adaptive strategies can be used to achieve high quality, low delay coding. The filters in these coders can be high-order (50 or more time lags) filters. Computational complexity and numerical stability of the algorithms is of prime concern for these filters. A number of new directions in the application of adaptive prediction in speech coding are also discussed.