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Abstract

A differential encoder for speech encoding, typically in a 16 kHz wide band, has a self adaptive predictive filter, comprising a comparator receiving, on an additive input, successive samples of a signal to be encoded and, on a subtractive input, an estimated signal delivered by a prediction loop which receives the error signal from the output of the comparator, the prediction loop comprising a self-adaptive predictive filter, a gain control circuit and a multiplier which receives the outputs of the predictive filter and of the gain control circuit and whose output is connected to the subtractive input. The predictive filter comprises a plurality of parallel channels assigned to different mutually adjacent spectral bands, each channel comprising an input pass-band filter, a quadratic detector fed by the pass-band filter, and a peak detector whose input is connected to the quadratic detector and whose output is applied to a multiplier which also receives the output signal from the respective pass-band filter, the outputs of all multipliers driving a common summer. A decoder for recovering the speech has a symmetric construction.

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First Claim