Rca Inc.

Kirk A Law

Leopold A Harwood

Robert F Casey

Danny Chin

A vertical transition processor for a comb filter detects the presence of a complementary-color vertical transition. A detector is provided for detecting if the color subcarrier on adjacent lines has the same phase angle and amplitude. This indicates the presence of a complementary-color vertical transition. If a complementary-color vertical transition is detected, then the comb filtered luminance and chrominance signals are selectively coupled to the luminance and chrominance processing channels so that the chrominance processing channel receives primarily color information and the color information is excluded from the luminance processing channel. This counteracts the adverse effects of the complementary-color vertical transition.

Vertical transition processor for a comb filter

A transition detector is disclosed which compares comb filtered component signals from adjacent image lines. A detector detects signals in the band of frequencies normally occupied by color representative information for a given line and two adjacent lines. A control signal generator generates a control signal in response to the relative levels of the detected signals for the given line, and the lines adjacent the given line. The composition of the comb filtered component signal coupled from the comb filter to the component processing channel is altered in response to the generated control signal.

Image transition detector

One-bit stream of clocked control information is applied to the input of delay means, having a succession of signal takeoff points, with the delay between successive takeoff points being the same (e.g., twice a period at the clocking frequency, f.sub.CL). Each takeoff point is linked to a respectively different input of an 'and' gate. The 'and' gate output is coupled to one input of a succession of two-input 'or' gates, with the other input of each of said 'or' gates coupled to the output of an associated one of a plurality of delay devices, each of the latter imparting the same delay (e.g., corresponding to a period of f.sub.CL). The output of the last of the succession of 'or' gates is coupled to a control signal output terminal. The output of each of the remainder of the succession is coupled to the other input of the next succeeding 'or' gate in the succession. The input of the delay device associated with the first 'or' gate of the succession is coupled to receive the output of an additional two-input 'or' gate. One input of the additional 'or' gate is responsive to the output of the 'and' gate, while the other input thereof is not signal-responsive, being maintained at a '0' level.

Duration-sensitive digital signal gate

In a color TV receiver, a first digital signal of 'm' bits represents high frequency component of combed luminance signal, and a second digital signal of 'm' bits represents combed chrominance component. The 'k' most significant bits of the first signal (where 'k' is less than 'm') are fed to respective inputs of a first 'or' gate, while the 'j' most significant bits of the second signal (where 'j' is less than, or equal to, 'm') are fed to respective inputs of a second 'or' gate. The 'or' gate outputs are fed, without delay difference, to inputs of a first 'and' gate, and are fed, with a delay difference of 90.degree. at color subcarrier frequency, to inputs of a second 'and' gate. Sequence recognition apparatus, responsive to the outputs of both 'and' gates, develops a correlation indication in response to existence of predetermined sequences of outputs from one or both 'and' gates. Control signal former, responsive to correlation indication, forms control signal for actuating high frequency component suppression in receiver's luminance channel to preclude hanging dot display.

Digital correlation indicator and hanging dot reduction system employing

Control signal generator is responsive to the output of a pair of correlation indicators. One correlation indicator provides an indication of the presence or absence of correlation between high frequency components derived without difference in delay from the respective luminance and chrominance outputs of a color TV receiver's comb filter system. The other correlation indicator provides an indication of the presence or absence of correlation between high frequency components derived with a difference in delay from the respective comb filter outputs, the delay difference corresponding to a quarter period at the nominal color subcarrier frequency. Control signal is developed in response to a correlation indication by either or both of the indicators. The luminance output of the comb filter is subjected to high frequency component removal during control signal development.

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East Windsor, NJ, United States of America

Kirk A Law