Video signal defect replacement circuitry

• US 4,368,483 A
• Filed: 06/22/1981
• Issued: 01/11/1983
• Est. Priority Date: 06/22/1981
• Status: Expired due to Fees

• Current Assignee: RCA Corporation
• Original Assignee: RCA Corporation
• Inventors: Liu, Frank C.
• Primary Examiner(s): Richardson, Robert L.
• Application Number:
  US06/276,011
• Time in Patent Office: 568 Days
• Field of Search: 358/8, 358/21 R, 358/36, 358/37, 358/160, 358/166, 358/167, 358/213
• US Class Current: 348/617
• CPC Class Codes: H04N 9/646 for image enhancement, e.g. vertical detail restoration, cross-colour elimination, contour correction, chrominance trapping filters
• CPC Class Codes: H04N 9/888 for signals recorded by pulse code modulation

Abstract

A video defect compensator is provided which develops a replacement or substitution video signal for use during a defect in the signal normally being displayed. The substitution signal is generated by averaging four picture points in the vicinity of the displayed picture point, two from the television line preceding the line currently being displayed and two from the television line succeeding the line currently being displayed. The four picture points are made available by utilizing a 2H delay line and wherein the line currently displayed is delayed by one TV line. Two signals temporally displayed by one color subcarrier period and delayed from the current signal by 1H are summed. Two signals temporally displaced by one color subcarrier period and preceding the currently displayed signal by 1H are also summed. The two sets of summed signals are then combined and divided by four to produce a replacement signal which is the average of four picture points.

Claims

1. A video signal processing system for providing defect compensation for a color video signal by substituting a replacement color signal for color video signal during the period of a video signal defect comprising:

a source of video signals;

first delay means for delaying said video signal by substantially one television line to provide a first signal;

second delay means coupled to said first delay means, said first and second delay means delaying said video signals by substantially two television lines to provide a second signal;

first combining means coupled to said source of video signals for combining signal therefrom temporally separated by one color subcarrier period, the combined signal being equal in color subcarrier phasing to said first signal;

second combining means responsive to said second signal for combining signals temporally separated by one color subcarrier period, the combined signal from said second combining means being equal in color subcarrier phasing to said first signal, and wherein the first signal is delayed from the combined signal from said first combining means by one television line and the combined signal from said second combining means is delayed from said first signal by one television line;

third combining means for generating a replacement signal proportional to the combined signals from said first and second combining means; and

switch means responsive to a defect signal for coupling said replacement signal to a video output terminal, and coupling said first signal to said video output terminal otherwise.

2. An improved signal processing circuit for generating a defect substitution signal for replacing portions of color video signals having noise or dropouts therein, said color video signal including a color subcarrier and having the signal segmented into image lines comprising:

a signal input terminal for applying video signal;

a first delay element having an input terminal connected to said signal input terminal and having an output terminal, said first delay element delaying said video signal by a period substantially equal to one image line plus one-half the color subcarrier period;

a second delay element having an input terminal connected to the output terminal of the first delay element and having an output terminal, said second delay element delaying said video signal by a period substantially equal to one image line less one-half the color subcarrier period;

a third delay element having an input terminal connected to said signal input terminal and having an output terminal, said third delay element delaying said video signal by a period equal to one subcarrier period;

a fourth delay element having an input terminal connected to the output terminal of the second delay element and having an output terminal, said fourth delay element delaying said video signal by one color subcarrier period;

first and second adder circuits having respective first input terminals connected to the input terminals of the third and fourth delay elements respectively and having respective second input terminals connected to the output terminals of the third and fourth delay elements respectively and having respective output terminals;

further circuitry having first and second input terminals connected respectively to the output terminals of the first and second adder circuits for generating at an output terminal thereof a signal proportional to the sum of the signals available from said adder output terminals; and

switch means responsive to a defect signal for applying signal from said further circuitry output terminal to a video output terminal, and applying signal from the first delay means output terminal to said video output terminal otherwise.

3. A video signal processing system for providing defect compensation for a color video signal by substituting a replacement color signal for the color video signal during the period of a defect comprising:

a source of video signals;

a tapped delay line having an input terminal coupled to said source of video signals, said delay line delaying video signal by at least two television lines plus one color subcarrier period and having first, second, third, fourth and fifth signal taps for respectively accessing video signal delayed from the first tap nearest the input terminal by one color subcarrier period, one television-line plus one-half color subcarrier period, two television lines, and two television lines plus one color subcarrier period;

first combining means for summing video signal from the first and second taps to produce a first summed signal;

second combining means for summing video signal from the fourth and fifth taps to produce a second summed signal;

third combining means for generating a replacement signal proportional to the sum of the first and second summed signals; and

switch means responsive to a defect signal for coupling said replacement signal to a video output terminal and coupling video signal from said third tap to said video output terminal otherwise.