| 摘要 |
PURPOSE:To improve the coding efficiency by quantizing only the effective data range of a difference signal while converting it into a characteristic being the object of quantization attended with the fluctuation of a threshold level so as to reduce the quantized error. CONSTITUTION:The change detection circuit of a transmission circuit outputs a difference signal based on the threshold level and a predication difference signal between an input signal and predicate signal calculated by a prediction circuit, a quantization circuit quantizes the difference signal and stores it tentatively in a transmission buffer circuit, and a local decoding circuit decodes the quantization signal locally. Further, a reception circuit is provided with a reception buffer circuit, a local decoding circuit and an adder. Then the quantization circuit consists of an adaptive quantization circuit including a characteristic selection circuit 8 selecting plural quantization characterstics of the circuit depending on the hershold level and a local decoding circuit consists of an adaptive local decoding circuit including a characteristic selection circuit 9 selecting the plural decoding characteristics of the circuit based on the threshold level so as to switch the effective data range of the difference signal into a characteristic being the object of quantization to apply quantization.
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