PURPOSE: To attain waveform processing without generating differentiating pulse, by applying a signal at reference point of time and a signal of a half period of a carrier to an amplitude correlation circuit in five comb line filters and correcting the waveform of the mixed signal.

CONSTITUTION: Outputs of amplifiers 22, 24 are added at an adder circuit 27 and a signal Sa is formed after being applied to an amplifier 28 having 1/2 gain. Further, outputs of amplifiers 24, 26 are added at an adder circuit 29, the result is applied to an amplifier 31 having -1/2 gain through a delay circuit 30 having 140nsec to form a signal Sb. The signals Sa, Sb are applied to the amplitude correlating circuit 32 having equation of (Sa>Sb) to form a signal Se. Further, the outputs of the adder circuits 27, 29 are added at an adder circuit 40, applied to an amplifier 41 having 1/4 gain to form a signal Sg. In inputting a step waveform, a pulse waveform and a chroma signal to an input terminal in this circuit, the chroma signal only is outputted from the waveform of each section and no differentiating pulse is outputted. Further, even if a step signal with a slope and a slant line signal are applied, no differentiating pulse appears at the output.