| 摘要 |
PURPOSE:To prevent deterioration of characteristics from being accumulated even with the titled circuits connected in cascade by outputting a representative residual value signal and a high/low both-limit residual value signal to an output of an adaptive inverse quantizing circuit and forming a nonlinear PCM decoding signal by these values. CONSTITUTION:When an ADPCM code nj is inputted to a terminal 8, an inverse adaptive quantizing circuit 91 outputs a representative residual signal corresponding to a residual signal ej at a coder side and ThU and ThL representing both limits of a section. A representative decoding signal, a lower-limit decoding signal XLj and a higher-limit decoding signal XUj are obtained by passing these values through adders 105, 106, an adaptive filter 111 and a fixed filter 112. The representative decoding signal is converted into a PCM quantizing signal X by a linear-nonlinear PCM converter 120, and the X is converted into a PCM quantizing signal XRj by a nonlinear-linear PCM converter 121. When the XRj exists in sections XLj, XUj, the XRj is used for a linear input to an ADPCM code circuit of the next stage. If the XR exists at the outside of the said sections, an output adding 1 to the XRj or subtracting 1 therefrom is obtained at a selecting circuit 124. |
