| 摘要 |
The comb filter (13.1) in the chrominance signal transmission channel (6) on the playback side of a videorecorder contains-in parallel with its retarder circuit (14)-an adder circuit (15) and a subtracter circuit (25) that have their signal outputs connected to a comparator circuit (30). Comparing the enveloping curves of the output signals (Sc and Sd) of the adder and subtracter circuits, the comparator then produces a switching signal (Sf) to reverse an electronic switcher (31) whenever the level of the enveloping curve of the subtraction signal is greater than the level of the enveloping curve of the addition signal. To this end, the level conditions of the two signals are set in such a manner that the level of the enveloping curve of the subtraction signal associated with a transition from a white background to a chrominance signal of a given intensity is greater than the level of the enveloping curve of the addition signal associated with the same color transition. Consequently, line-parallel color transitions that become color-disturbed due to the action of the comb filter are readily recognized and can be replaced by switching to an undisturbed chrominance signal (Sa).
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