13.4 Adaptive Prediction
The prediction gain to be had in classical predictive coders is proportional to the ratio of the signal variance to prediction-error variance. This is because for a fixed quantizing noise level, fewer bits are required to describe a signal with smaller energy. The utility of the predictive coder is limited by possible mismatches between the source signal and the predictor filter. The sources of mismatch are related to the time-varying behavior (i.e., nonstationarity) of the amplitude distribution and of the spectral or correlation properties of the signal. Adaptive encoders incorporate (slow-time) auxiliary loops to estimate the parameters required to obtain locally optimal performance. These auxiliary loops periodically ...
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