| 摘要 |
An apparatus for fully reducing quantization distortion of a digital signal, which includes at least one digital low-pass filter, a counter, a selector and a corrector. Each of the digital low-pass filter(s) operates to pick up predetermined low frequency components from an input digital signal while expanding downward its bit length so as to obtain an output digital signal having the expanded bit length. The counter counts the number of consecutive samples having a same quantized level before and after each sample point of the input digital signal. And, in accordance with the count value of this counter, the selector selects and outputs either the input digital signal whose bit length was expanded downward or a digital signal passed through any one of the digital low-pass filters. Further, the corrector operates to make a discontinuous point (contained in the output of the selector) continuous. Thus, the apparatus allows its output signal to smoothly vary without unnecessarily attenuating the high frequency components.
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