JP2853824B

PURPOSE:To evade the propagation of a code error, maintain a relatively short update period, and to reduce quantization distortion by utilizing the time continuity of parameters when spectrum information and power are encoded with a small amount of information. CONSTITUTION:A multiplier 1 multiplies a past code vector Vj which is one frame before by a coefficient (1-g) and supplies the result to one input terminal of an adder 2. A code (g) is the constant of the rate of a weighted mean. Further, a multiplier 3 multiplies a current regenerated vector Wk by the constant (g) of the rate of the weighted mean and supplies the result to the other input terminal of the adder 2. The adder 2 adds the vectors supplied to the respective input terminals and supplies the result as a quantized value Yn to a distortion calculator 4. The distortion calculator 4 is supplied with an ideal parameter Xn, selects and supplies a regenerated vector Wk, minimizing the distortion between the quantized value Yn and input parameter Xn, to the multiplier, and also sends its number.