| 摘要 |
PURPOSE:To improve an accuracy in detecting a digital synchronous signal by judging an amplitude and the periodic characteristic of the horizontal synchronous signal section of a composite synchronous signal separated from a video signal, recognizing it as the horizontal synchronous signal only when it coincides with a fixed condition and using the horizontal synchronous signal having high accuracy for a digital synchronous detection. CONSTITUTION:From a synchronous separating signal 19, an amplitude detecting pulse 202 is obtained, a succession and a periodic characteristic of this amplitude detecting pulse 202 are measured to obtain a detecting pulse 204 and a cycle measuring data 205 and a difference 211 between an average value 209 of the cycle of the horizontal synchronous signal obtained by integrating the cycle measuring data 205 and the cycle measuring data 205 is obtained. Only when this difference is small, a horizontal synchronous detecting pulse 21 is outputted and the horizontal synchronous signal is detected highly accurately. The horizontal synchronous detecting pulse 21 has its accuracy effectively equal in said cycle corresponding range. In this manner, the horizontal synchronous signal 21 detected highly accurately is supplied to a timing generating circuit 7. Thereby, the timing generating circuit 7 generates a very precise digital synchronous timing pulse 22. |
