a signal processing circuit for certainly detecting presence or absence of a change in the vertical direction of amplitude and phase of a chrominance signal by once converting the change in the vertical direction of amplitude and phase of the input chrominance signal into a change in the direction of amplitude by a converter , then comparing the converted output with a signal obtained by passing the converted output through one or a plurality of delay circuits by one or a plurality of comparing circuits in amplitude level , and then making an operation with the output of the comparing circuit by an operational circuit .