| 摘要 |
In a composite video signal that contains an image field having vertical synchronization (V-Sync) pulses, The V-sync pulses include first equalization pulses of E1 waveforms followed by a serration pulses of S waveforms, TS-long each, followed by a second equalization pulse of E2 waveforms, TE-long each. The transition from a last waveform of the E1 waveforms to a first waveform of the S waveforms constitutes a vertical synchronization (V-sync) signal. The system a reference event occurring at a first time interval DELTA T 1+/-Er after said V-sync signal, wherein Er stands for time shift error. The system includes filter for filtering the composite video signal so as to obtain a filtered signal. Clamper for clamping the filtered signal so as to obtain a clamped signal. First detector for detecting N (N</=S) waveforms in the serration pulses thereby indicating first event occurrence. Second detector for detecting M (M</=E2) waveforms in the second equalization pulses, thereby determining the reference event occurrence, such that the DELTA T 1 equals M*TE+S*TS.
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