| 摘要 |
PROBLEM TO BE SOLVED: To discriminate the kind of input video signals from a horizontal synchronization width. SOLUTION: A falling edge of horizontal synchronization signals HD is detected by an edge detection section 11. Moreover, the phase of the signals HD is inverted by an inversion section 12. A counter 13 is cleared by the edge detected by the section 11, counts clock signals(CLK) in the interval of the horizontal synchronization signals from the section 12 and outputs the count data to first to third decoders 14, 15 and 16. Setting values D1, D2 and D3 (where D1<D2<D3) are set in these decoders and when input count data exceed respective setting values, these decoders output a high (H) level. These decoder outputs are outputted through flip-flops 17 and 20 as detected signals S1, S2 and S3. These signals yield different combinations corresponding to the horizontal synchronization amplitudes and a signal kind is discriminated from the combinations.
|
