Patent ID: 7295248

Claim:
A circuit that generates an external synchronous signal, the circuit comprising: means for inputting an external frame synchronous signal (FRM_SYNC) as well as a frame synchronous signal (FRM) and a horizontal synchronous signal (HBK) of a digital video signal; means for measuring a phase difference between the external frame synchronous signal (FRM_SYNC) and the frame synchronous signal (FRM) of the digital video signal; means for generating a signal (EXT_H) having the same period as that of the horizontal synchronous signal (HBK) of the digital video signal, the signal (EXT_H) having the measured phase difference with reference to the frame synchronous signal (FRM) of the digital video; and means for generating a signal (EXT_F) having the same period as that of the frame synchronous signal (FRM) of the digital video signal, the signal (EXT_F) having the measured phase difference with reference to the frame synchronous signal (FRM) of the digital video, wherein the generated signals (EXT_F) and (EXT_H) are outputted as an external frame timing signal and an external horizontal timing signal of the external synchronous signal.