| 摘要 |
PURPOSE:To provide an excellent quantizing characteristic by providing a polygonal line approximation means to a logarith converter and an inverse polygonal line conversion means to an inverse logarithmic converter so as to reduce quantized noise produced by the logarithmic and inverse logarithmic conversion. CONSTITUTION:The polygonal line approximation means is provided to the logarithmic conversion section of an adaptive quantizer, the mantissa part is approximated by polygonal lines and a polygonal line aprroximation inverting means is provided to the inverse logarithmic conversion section to apply the inversion. An input signal d(K) is converted into a logarithm by the logarithmic converter 1, a scaling constant generated by an adaptive controller 4 is reduced by a subtractor 2 and quantized by a quantizer 3. The quantized output value I(K) is inversely quantized by an inverse quantizer 5, the scaling constant generated by the adaptive controller 4 is added again by an adder 6, the result is subject to inverse logarithmic conversion by an inverse logarithmic converter 7 to obtain an inverse quantized signal dp(K). Thus, the distortion by the logarithmic, inverse logarithmic conversion is reduced and the quantized noise by the adaptive quantization noise.
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