JPH0480593B

PURPOSE:To offset diffused signals without the information of horizontal cycle so as to obtain excellent pictures, by finding the voltage difference between fields of a reference voltage inserted into a vertical blanking period and changing the time of the flat section of a staircase wave in accordance with the found voltage difference. CONSTITUTION:FM-demodulated high-definition TV signals are inputted from an input terminal 1 and supplied to the 1st AD converter 5. Signals sampled and quantized at the AD converter 5 are supplied to the 1st gate circuit 6 and the digital value of a reference voltage period is gated by a gate pulse inputted from another input terminal 2. The digital value is supplied to a change-over switch 8 after it is subjected to addition and averaging operation and a mean value in the vicinity of the rise of a diffused signal and another mean value in the vicinity of the fall of the diffused signal are separated from the digital value and outputted by the switch 8. By detecting the maximum and minimum values of the diffused signal from the two mean values and finding the difference between them at a subtractor circuit 11, the counting value of a counter 13 is controlled with the output of the subtractor circuit 11 and the time of the flat section of a staircase wave for correction is changed.