| 摘要 |
A decoder that provides simultaneous horizontal scanning lines for digital color video, and then band splits each line into high and low frequency signals using low pass filters and subtractors to subtract the low frequency signals from the source video. The high and low frequency signals and the source video for each line is fed to a three tap comb filter, and the high and low frequency signal inputs to the comb filter are also fed to a vertical transition detector that demodulates the high frequency signals, and then provides differences between pairs of lines for luma, chroma magnitude, and chroma phase. The difference signals are used to provide a control signal that automatically switches the comb filter from a three line weighted comb to a two line comb when large vertical transitions are detected in luma, chroma magnitude, or chroma phase. The difference signals are also used to address a programmable RAM which provides a multiplier term for the comb filter output which is then mixed with a selected one of the high and low frequency signals. Thus, the multiplier term determines the degree of cross fade between a simple filtered and a comb filtered output.
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