Circuit for and method of detecting a color field sequence of a color video signal
First Claim
1. A method for digitally detecting a color field in a color field sequence of a color video signal having a horizontal sync and a color burst which have a given phase relationship with a color subcarrier, comprising:
- determining the location in time of at least one cycle within the color burst of a video line relative to the leading edge of the same video line'"'"'s horizontal sync;
supplying at least one sample pulse during said at least one cycle;
generating in response to said at least one sample pulse at least one selected value within said cycle of the color burst which value is indicative of the phase relationship of the color burst relative to the horizontal sync in the same video line; and
detecting the sequence of occurrence of successive selected values to determine said color field in the color field sequence.
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Accused Products
Abstract
A color field 1 detector includes analog and digital processor sections, wherein the analog processor section receives a video signal input and provides the digital signals necessary to drive the digital processor section. A timing generator receives a free-running reference clock and supplies an internal reference signal of subcarrier frequency starting at the falling edge of composite sync. A burst phase comparator compares the incoming color burst phase to the internal reference signal phase and generates logic signals indicative of the phase relationships therebetween to thus indicate whether the color burst is in phase, 180° out of phase, or if any phase error exists. A state machine receives the logic signals and detects the sequence of occurrence of the states of the color burst relative to the internal reference signal. The sequence is indicative of the subcarrier-to-composite sync phase of the video signal input for the particular color television standard. The state machine provides a field reference signal in the form of a selected logic level which identifies the color field 1 of the color field sequence for the standard.
17 Citations
23 Claims
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1. A method for digitally detecting a color field in a color field sequence of a color video signal having a horizontal sync and a color burst which have a given phase relationship with a color subcarrier, comprising:
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determining the location in time of at least one cycle within the color burst of a video line relative to the leading edge of the same video line'"'"'s horizontal sync; supplying at least one sample pulse during said at least one cycle; generating in response to said at least one sample pulse at least one selected value within said cycle of the color burst which value is indicative of the phase relationship of the color burst relative to the horizontal sync in the same video line; and detecting the sequence of occurrence of successive selected values to determine said color field in the color field sequence. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A circuit for detecting a color field in a color field sequence of a color video signal having a horizontal sync and a color burst which have a given phase relationship with a color subcarrier, comprising:
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means responsive to the horizontal sync for determining the occurrence of a selected cycle within the color burst duration relative to horizontal sync; means responsive to the determining means for comparing the phase of the color burst with the phase of the previous horizontal sync, and for generating state signals indicative of states of the color burst when it is in phase, or on the order of 180°
out of phase; andmeans responsive to the state signals for detecting the sequence of occurrence of the states to identify said color field in the color field sequence. - View Dependent Claims (12, 13, 14, 15, 16)
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17. A circuit for detecting color field 1 in a color video signal having a horizontal sync and a color burst which have a given phase relationship with a color subcarrier, comprising:
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means for generating internally a reference signal at subcarrier frequency starting at a selected phase relationship with a leading edge of said horizontal sync in a selected video line; means responsive to said generating means for supplying multiple sample pulses during selected cycles of the color burst; means coupled to the generating means and responsive to the supplying means, for comparing the color burst with the reference signal during said selected cycles, and for providing state signals indicative of the phase relationship between the color burst and the reference signal; and means responsive to the state signals for detecting a sequence of successive selected phase relationships to identify the color field 1. - View Dependent Claims (18, 19, 20)
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21. A circuit for detecting a color field sequence of a color video signal, comprising:
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means responsive to the color video signal for producing therefrom an odd field digital signal, and horizontal sync and color burst digital signals which have a selected phase relationship with a color subcarrier; means for supplying a free-running reference clock having a preselected frequency commensurate with a given color television standard; means receiving the reference clock and responsive to the horizontal sync for generating an internal reference signal at the color subcarrier frequency starting at a selected phase relationship with a leading edge of the horizontal sync, a state clock signal, and selected sample pulses occurring during corresponding half-cycles of the color burst signal; means responsive to the selected sample pulses for phase comparing the color burst signal with the internal reference signal to provide selected state signals indicative of phase relationships therebetween; and means receiving the selected state signals and responsive to the state clock signal for detecting the sequence of occurrence of said phase relationships, to identify the color field sequence. - View Dependent Claims (22, 23)
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Specification