PURPOSE: To use correlation with a preceding frame and to eliminate the need for solving a polynomial by synthesizing a predicted value from a linear predictive device with a regenerated residual signal from a forward adaptive coder at an adder and generating a regenerative signal.

CONSTITUTION: A difference between a predictive value by a backward adaptive prediction device 1 and an input signal is given to a subtractor 23 and a linear prediction analysis section 21. The analysis section 21 applies linear prediction analysis to the predictive residual signal and sends the result to a transmission line in the form of a code word and given to a predictive device 22 by giving a parameter. A forward predictive value from the predictive device 22 and a backward residual signal from a subtractor 3 are given to a subtractor 23, the residual signal is quantized and coded by a quantization section 24 and the regenerative signal of a forward residual signal is outputted. The signal and the predictive value from the predictive device 22 are added by an adder 26, the backward residual signal is regenerated and the regenerative signal is obtained by an adder 4. Thus, the correlation with a preceding frame is utilized and the solution of the polynomial is not required.