Ghost cancelling system that cancels ghosts from video signals with a transversal filter
First Claim
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1. A ghost canceling system comprising:
- a transversal filter having a plurality of taps which coefficients are adjustable;
a subtractor which subtracts an output signal of said transversal filter from an input video signal, including a ghost signal and a vertical synchronization cyclic reference signal, and outputs the result of the subtraction operation to said transversal filter;
a memory means for maintaining the waveform of an output from said subtractor;
an error detection means for comparing said output waveform from said subtractor maintained in said memory means and a reference signal; and
control means for controlling the correction of said tap coefficients in response to an output from said error detection means;
wherein said control means judges whether an equilibrium condition exists wherein said ghost signal has been substantially canceled from said video signal, corrects each tap coefficient in response to a detected result of said error detection means until the equilibrium condition is reached, but corrects only said tap coefficients which have absolute values equal to or greater than a specified value after the equilibrium condition is reached.
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Abstract
A ghost cancelling system which distinguishes whether ghosts have been substantially cancelled from a video signal for finding an equilibrium condition. The system calculates a specified value which depends on the noise signal contained in the video signal. The tap coefficients which are equal or greater than the specified value are then detected, and the system corrects only those tap coefficients after the equilibrium condition exists.
17 Citations
15 Claims
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1. A ghost canceling system comprising:
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a transversal filter having a plurality of taps which coefficients are adjustable; a subtractor which subtracts an output signal of said transversal filter from an input video signal, including a ghost signal and a vertical synchronization cyclic reference signal, and outputs the result of the subtraction operation to said transversal filter; a memory means for maintaining the waveform of an output from said subtractor; an error detection means for comparing said output waveform from said subtractor maintained in said memory means and a reference signal; and control means for controlling the correction of said tap coefficients in response to an output from said error detection means; wherein said control means judges whether an equilibrium condition exists wherein said ghost signal has been substantially canceled from said video signal, corrects each tap coefficient in response to a detected result of said error detection means until the equilibrium condition is reached, but corrects only said tap coefficients which have absolute values equal to or greater than a specified value after the equilibrium condition is reached. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method for controlling a ghost canceling system including a transversal filter connected to receive an input video signal including ghost signals and a vertical synchronization cyclic reference signal, the method including the steps of:
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canceling said ghost signal from said input video signal using said transversal filter; detecting an error signal between said reference signal included in said canceled signal and pre-stored reference signal; distinguishing whether an equilibrium condition exists wherein ghost signals have been substantially eliminated from a signal passed through said transversal filter; calculating a specified value which depends on a noise signal contained in said video signal; detecting the tap coefficients which have absolute values equal to or greater than said specified value; and correcting said each tap coefficient in response to said detected error signal until said equilibrium condition is reached, but correcting only said detected tap coefficients.
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Specification