| 摘要 |
PURPOSE:To attain noise elimination with higher accuracy by detecting the noise level of a synchronizing part of a video signal through a circuit containing a cyclic filter and controlling the parameter of a noise eliminating filter based on said noise level. CONSTITUTION:A video signal SV is supplied to an input terminal 1 as well as to a cyclic filter 200 consisting of mixture ratio circuits 19 and 22, an adder 20 and a delay line 21 to a subtractor 23 respectively. At the same time, the output of the adder 20 is supplied to the subtractor 23 ad the output of the subtractor 23 is supplied to a D value control circuit 24. A setting circuit 24A controls the value of K of the filter 200 based on the output SB of the subtractor 23. Therefore, the value of K is set closer to 1 as the change is reduced less toward the vertical direction. Here the filter 200 is approximated to such characteristics that are shown by a solid line (a). While the value of K is set closer to 0 and the change is increased toward the vertical direction. Then the filter 200 is approximated to the characteristics shown by a solid line (b). Thus the noise component can be eliminated more effectively as the change is reduced toward the vertical direction for an output video signal SVO which is obtained from an output terminal 6.
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