Ghost cancelling device with waveform checking circuit

Abstract

A ghost cancelling device including a filtering portion made up of a transversal filter for cancelling a ghost component included in input video signals, a waveform extracting circuit for extracting a part, which corresponds to a predetermined period of time and includes a reference signal for cancelling a ghost, of a signal included in the input video signal, a waveform converting circuit for performing the waveform conversion of the signal corresponding to the predetermined of time and extracted from the input video signal, a subtracter for comparing an output of the waveform converting circuit with a preset reference waveform and outputting a signal in accordance with the result of the comparison, a coefficient setting circuit for setting coefficients having values in accordance with the output signal of the subtracter and a waveform checking circuit interposing between the waveform extracting circuit and the waveform converting circuit. The waveform checking circuit decides whether or not the output of the waveform extracting circuit should be sent to the waveform converting circuit. Thus, the ghost cancelling device can interrupt an operation of cancelling a ghost when the input video signal is abnormal and prevent occurrence of a malfunction and a runaway.