Differential coder with auto-adaptive predictor filter, with rapid gain adaption, and corresponding decoder

摘要

The invention relates to a differential coder with auto-adaptive predictor filter. The coder comprises a comparator (12) and a prediction loop including an auto-adaptive predictor filter (14) with several channels, an automatic gain circuit (16) and a multiplexer (18). The circuit (16) allows the gain to be adapted on the basis of k+1 successive values DELTA (n-k) to DELTA (n) according to the law: if G(n), current value of gain GC(n-1), previous value of the peak gain, then: GC(n) = f .G(n) if G(n) = GC(n-1), f = dispersion coefficient, or else GC(n) = G(n) if G(n) GC(n-1). For each pair of successive values DELTA (n-(j-1)), DELTA (n-j), a state variable is defined IMAGE with pj = 2k - jJ if DELTA (n-(j-1)) = DELTA (n-j), or otherwise pj = 0, and delta (C DELTA (n)) coefficients are defined with delta C( DELTA n) k - 1 delta C( DELTA n) 1 if 2k - 1 = C DELTA (n) k. The current value of the gain G(n) satisfies the relationship G(n) = delta (C DELTA (n)) x G(n-1) if the calculated value of G(n) is greater than a reference value u x GC(n). Application to speech coding/decoding in telephony. IMAGE