| 摘要 |
PURPOSE:To stabilize a discriminating operation by allowing a count control circuit to identify whether a PAL ident signal has a positive phase of a negative phase, controlling a counter circuit depending on the result of identification and giving a threshold value. CONSTITUTION:An analog video signal to an input terminal 21 is converted into a digital video signal by an A/D converter 22 and fed to a sampling phase circuit 24. Then the sample of a color burst signal is extracted by using a timing signal from a timing generator 25 to obtain a burst phase detection signal BPD. The signal BPD is fed to a system detection section 100 and a phase locked loop (PLL) control circuit 26. The system detection section 100 uses a burst detection signal BPD and timing signals T2-Tn to obtain a PAL/ NTSC detection signal P/N and a PAL ident signal PID. The signals are fed to a video processing circuit 27 to switch the digital video signal processing mode of the processing circuit.
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