| 摘要 |
A method and circuit for recovering from a video signal a digital Vertical Interval Time and Control Code (VITC) signal which has been distorted in the recording process. The video signal is passed through an appropriate high pass (differentiating) filter to remove all but the narrow spectrum associated with the rising and falling edges of the NRZ modulated VITC signal. Optionally, the signal may be low-pass filtered to improve noise immunity and remove any chroma or burst frequency components. The resulting output signal is a separate series of positive and negative pulses with an average DC value of zero. These pulses correspond to the rising and falling edges of the original VITC signal, are detected and used to reconstruct the original VITC signal. The positive pulses are delayed and then used to set a flip-flop while the negative pulses are used to reset the flip-flop. The output of the flip-flop will substantially correspond to the original VITC signal.
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