Detection of onset of ghost image cancellation reference signal - discriminates against video signal pedestal by threshold comparison of duration of excess of difference between successive inputs.

摘要

The method involves using a differential value detector (10) for securing the differential values of a ghost cancellation reference signal and the pedestal signal of the video input by subtraction (12) of delayed (1) and undelayed signals. The difference is compared (20) with a set threshold and if this is exceeded a counter (30) records the duration of the excess for further comparison (40) with another set threshold. A ghost cancellation reference signal (GCR) is produced when the min. duration is exceeded. USE/ADVANTAGE - With TV signals distorted by multipath interference and reflections. Continuous eight field ghost cancellation reference signal can be distinguished unambiguously from pedestal signal.