| 摘要 |
PURPOSE:To obtain accurately a vertical synchronizing signal even when it is not detected due to drop-out, etc., by measuring for the certain scanning period with a digital counter. CONSTITUTION:After measuring 245 pulses for the NTSC method, or 294 pulses for the PAL/SECAM method, the counter 3 or 6 counts the period till the following vertical synchronizing signal is detected. Depending upon whether the counter 3 or 6 is an even number or odd number, respectively, the switching device 11 is switched. After the mean value of the values which were measured by the counter 3 or 6 is calculated by the mean value calculators 4 and 7, this mean value is stored in the memory 5 and 8. When the vertical synchronizing signal cannot be detected due to drop-out, etc., the vertical synchronizing signal is accurately generated based upon the data which are stored in the memory 5 and 8. |
