ADAPTIVE DIFFERENTIAL PCM SYSTEM WITH RESIDUAL-DRIVEN ADAPTATION OF FEEDBACK PREDICTOR

摘要

An adaptive differential pulse code modulation system (ADPCM), with adaptive prediction, has a transmitter (10A), which substracts the output of its predictor (18) from the original input signal and transmits a numeric representation of the quantized difference, and a receiver (12A) which reconstructs the original input signal by the reverse process. Mistracking, whereby the receiver fails to faithfully reproduce the original input signal because its predictor coefficients differ from those of the transmitter predictor, which can result from transmission errors when the original signal comprises two pure tones, is avoided by eliminating the dependence of the adaptation process upon the predictor output. This is achieved by deriving the coefficients using the difference signal but not the reconstructed signal at the output of the predictor.