| 摘要 |
PURPOSE:To prevent the deterioration in characteristic from being accumulated by outputting a representative residual signal and both high and low limit residual signals to an output of an inverse adaptive quantizing circuit and correcting a representative decoding signal by the values so as to form a nonlinear PCM decoding signal. CONSTITUTION:When an ADPC code nj is inputted to a terminal 8, the inverse adaptive quantizing circuit 91 outputs a value multiplying the representative value in response to the code nj and a threshold value by a present quantizing width DELTAj. This output signal has a value of a representative residual signal ej corresponding to a residual signal ej of the decoder and a value representing both limits of a section of a signal value represented by the representative residual signal ej, and the larger value is taken as THU and the smaller value is taken as THL. Since an adaptive filter 111 and a fixed filter 112 output a forecast value at present time, a representative decoding signal xj is obtained by adding an output forecast value of the filters 111, 112 by adders 101 and 102 respectively to the representative residual signal ej. The deterioration in characteristic is not accumulated by correcting this signal xj so as to form a nonlinear PCM decoding signal. |
