VERTICAL SYNCHRONIZING SIGNAL GENERATION DEVICE AND VIDEO SIGNAL PROCESSOR

摘要

PROBLEM TO BE SOLVED: To provide a vertical synchronizing signal whose period is stable and to provide a signal synchronized with the vertical synchronizing signal of an input signal even if the vertical synchronizing signal included in the input signal alternately repeats the two periods. SOLUTION: A device is provided with a vertical synchronizing signal separating circuit separating the vertical synchronizing signal of an input luminance signal and outputs it as a first vertical synchronizing signal, an automatic frequency control circuit generating and outputting a second vertical synchronizing signal having a repetition frequency equivalent to the average repetition frequency of the first vertical synchronizing signal, a vertical synchronizing signal phase detection circuit detecting whether the first vertical synchronizing signal alternately repeats the two periods and outputting the detection result as a discrimination signal and a selector receiving the first and the second vertical synchronizing signals and selecting and outputting the first vertical synchronizing signal when the discrimination signals shows that the first vertical synchronizing signal alternately repeats the two periods and the second vertical synchronizing signal in the other cases.