| 摘要 |
PURPOSE:To improve the instability of framing discrimination due to temperature change, by processing digitally a composite synchronizing signal. CONSTITUTION:In discriminating an even and an odd number field forming one frame of a video signal, a non-retriggerable monostable multivibrator 23 which is triggered at a tail ridge of a horizontal synchronizing signal and generates an output longer than a 1/2 period and shorter than one period is operated. The even and the odd number field is discriminated by sampling this output with a clock formed with the vertical synchronizing signal. Further, in Figure, 1 is a composite synchronizing signal separating circuit, 21 is a monostable multivibrator having a metastable state time longer than the width of the horizontal synchronizing signal and shorter than the equivalent signal width of the vertical synchronizing signal, 22, 24, 25 are D flip-flops, 26 is a differentiation circuit and 6 is a frequency divider. |
