| 摘要 |
<p>PURPOSE:To improve the average efficiency of data compression by quantizing a differential signal by a nonlinear characteristic whose center is a differential reference value, and allocating a variable length code to the quantized differential signal centering on the area corresponding to a predicted value which is predicted from the differential reference value. CONSTITUTION:An predicated value xi' outputted from a predictor 18 is supplied to the pulse side of an adder-subtractor 25. An output from the adder-subtractor 25 xi'-xi-1 is quantized by a nonlinear quantizer 26 having the same characteristic as that of the quantizer 14 from which a representative value corresponding to the differential value xi'-xi-1. In this case, the difference of the current value with the preceding value xi-1 is nonlinearly quantized centering on the preceding value xi-1, and such one as of short work length among the variable length codes is allocated to the result of the quantization centering on the representative value corresponding to the predicted value xi'. Therefore, a two-bit code is allcated to a value in the approximation to the predicted value xi'. The farther the predicted value xi' is away from the preceding value xi-1, the wider the area of said two bits is. Since the xi is in the close approximation to the predicted value xi' with an extremely high probability, the two-bit code is selected with a high probability, hence an extremely high data compression ratio can be accomplished.</p> |
