| 摘要 |
PURPOSE:To discriminate a field with simple constitution, by separating a horizontal and a vertical synchronizing signals from an input composite video signal, detecting a phase difference between the horizontal synchronizing signal and the vertical synchronizing signal, and discriminating the field. CONSTITUTION:A composite synchronizing signal A separated from the composite video signal is added on a monostable multivibrator 12 and a D flip-flop(D- FF) circuit 15. The monostable multivibrator 12 is held with a monostable multivibrator 13, and furthermore, the Q outputs and Q outputs of both monostable multivibrators are added on an AND circuit 14, and the horizontal synchronizing signal is taken cut from the AND circuit 14. Meanwhile, the Q output of the monostable multivibrator 12 is added on the clock terminal of the D-FF circuit 15, and the vertical synchronizing signal can be obtained from the Q output. The vertical synchronizing signal and the horizontal synchronizing signal are inputted to a NAND circuit 18, and a field discriminating signal can be obtained from the NAND circuit 18. The field discriminating output is sent to a J-K-FF circuit 17, and the field discriminating output is outputted from the circuit 17.
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