| 摘要 |
The video signal processing circuit has a clamp circuit for clamping a composite video signal including a copy guard signal with amplitude of from white to black as well as a pseudo horizontal synchronization signal, a brilliant signal, and a synchronization signal. The circuit also has a synchronization signal separation circuit, which separates the synchronization signal from the composite video signal and a synchronization signal discrimination circuit, which identifies if the synchronization signal coming from the synchronization signal separation circuit has the same cycle as that of a horizontal synchronization signal, and which blocks the signal with the cycle shorter than the cycle of the horizontal synchronization signal, letting only the signal with the cycle of the horizontal synchronization signal pass. The clamping of the composite video signal is performed correctly even during the period when clamp pulse based on the pseudo horizontal synchronization signal with a shorter pulse width in the copy guard signal period is used.
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