| 摘要 |
PURPOSE:To set the control of a noise removal circuit to be satisfactory with simple circuit constitution by executing control in accordance with the error flag of an error correction circuit so as to return a signal to a correct PCM sound signal. CONSTITUTION:The pulse of the error flag in the error correction circuit of a PCM decoder 2 is supplied to an integrating circuit 16. It obtains a pulse as a DC detection signal corresponding to a duty ratio and supplies it to the variable gain amplifier circuit 1e of the noise removal circuit 1 as a gain control signal. When a C/N value is deteriorated, the duty ratio in the high level of the error flag becomes large, and a DC detection signal becomes large. Since the circuit 1 is controlled in accordance with the error flag of the error correction circuit provided for the PCM decoder 2, the DC detection signal obtained through the circuit 16 is proportional to the C/N value of an input signal. Thus, the circuit 1 is controlled by the C/N value and noise removal quantity increases in accordance with the deterioration of the C/N value. Then, the detection circuit of the detection value of the C/N value becomes unnecessary, and the circuit 1 can satisfactorily be controlled with simple constitution.
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