| 摘要 |
PROBLEM TO BE SOLVED: To provide a video signal detection circuit capable of generating a vertical synchronizing signal at appropriate timing even though a video signal in which the number of pixels per screen is not a specified value is inputted. SOLUTION: A vertical synchronizing signal is detected from an input video signal Y, and a pixel counter 20 starts to count pixel clocks with the vertical synchronizing signal 32 and keeps counting until its counted value reaches a prescribed number. The prescribed number is set to be equal to the number of pixels per screen defined in a standard method. Meanwhile, a comparator circuit 30 compares the detected vertical synchronizing signal 32 with the counted value 26 and outputs their difference 34 to a differential register 36. The differential register 36 and an averaging circuit 42 average the difference with respect to n screens of the input video signal Y and output its average value 24 to an addition circuit 22. The addition circuit 22 delays the vertical synchronizing signal 32 in accordance with the average value 24 and outputs the signal adjusted in this way as a vertical synchronizing signal VD from a device output 14. COPYRIGHT: (C)2003,JPO
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