Noise reduction system for video signals
First Claim
1. A noise reduction system for reducing noise in a video signal which consists of a plurality of successive frames occuring at frame intervals, comprising:
- means for storing at least one frame of said video signal for an integral multiple of said frame intervals;
means for mixing corresponding elements of a new frame of said video signal with said video signal stored in said means for storing to produce a frame difference signal;
means for transforming said frame difference signal into a plurality of video signal components;
means for respectively controlling the plurality of video signal components whereby a predetermined characteristic of at least one of said plurality of video signal components is modified;
means for recombining said plurality of video signal components including said at least one modified component into a corrected frame difference signal; and
means for combining said corrected frame difference signal with said new frame of said video signal to obtain a noise-reduced video signal.
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Abstract
A recursive noise reduction system for a television system uses the spatial correlation in a frame difference signal derived by element-by-element subtraction of an incoming video signal from corresponding picture elements of a relatively noise-free stored video signal to redue noise in a video signal. The spatial correlation is used to suppress the components of the frame difference signal which are due to frame-to-frame changes in the video resulting from motion in the scene, thus producing a signal which contains substantially only the noise in the incoming video. The noise signal thus derived is subtracted from the incoming video signal to produce a noise-reduced output signal for display or recording. The noise-reduced output signal and the incoming video are added together in varying proportions according to the amount of scene-to-scene motion detected and the sum is stored for use in subsequent treatment of new incoming video.
53 Citations
28 Claims
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1. A noise reduction system for reducing noise in a video signal which consists of a plurality of successive frames occuring at frame intervals, comprising:
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means for storing at least one frame of said video signal for an integral multiple of said frame intervals; means for mixing corresponding elements of a new frame of said video signal with said video signal stored in said means for storing to produce a frame difference signal; means for transforming said frame difference signal into a plurality of video signal components; means for respectively controlling the plurality of video signal components whereby a predetermined characteristic of at least one of said plurality of video signal components is modified; means for recombining said plurality of video signal components including said at least one modified component into a corrected frame difference signal; and means for combining said corrected frame difference signal with said new frame of said video signal to obtain a noise-reduced video signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
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26. A noise reduction system for reducing noise in a video signal which consists of a plurality of successive frames occurring at frame intervals, comprising:
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a frame memory operative to store at least one of said frames; a means for producing a frame difference signal responsive to element-by-element difference between corresponding elements of a new frame and a frame stored in said frame memory; an area change detector responsive to said frame difference signal for producing a change signal responsive to frame-to-frame change in an area of said video signal near said elements to which said means for producing a frame difference signal are responsive; a video suppression circuit including a signal transform circuit, a non-linear circuit assembly and a signal recombination circuit; said signal transform circuit including means for producing a parallel plurality of orthogonally transformed signal components of said frame difference signal; said non-linear circuit assembly including a plurality of non-linear circuits, each of said plurality of non-linear circuits being responsive to said change signal to control the passage therethrough of one of said parallel plurality of orthogonally transformed signal components whereby change-induced components are removed therefrom; said signal recombination circuit including means for orthogonally retransforming said parallel plurality of orthogonally transformed signal components from said non-linear circuit assembly into a serial corrected frame difference signal corresponding to said frame difference signal with said change-induced components removed; a subtractor for subtracting said correct frame difference signal from said new frame whereby a noise-reduced video signal is produced; and proportioning means responsive to said change signal for feeding a proportional mixture of said new frame and said noise reduced video signal to said frame memory for storage therein.
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27. A noise reduction system for reducing noise in a video signal which consists of a plurality of successive frames occurring at frame intervals, comprising:
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a frame memory operative to store at least one of said frames; means for producing a frame difference signal responsive to element-by-element differences between corresponding elements of a new frame and a frame stored in said frame memory; a video suppression circuit including a signal transform circuit, a plurality of gain control amplifiers and a signal recombination circuit; said signal transform circuit including means for producing a parallel plurality of orthogonally transformed signal components of said frame difference signal; each of said plurality of gain control amplifiers being operative to control the passage therethrough of one of said parallel plurality of orthogonally transformed signal components whereby change-induced components are removed therefrom; said signal recombination circuit including means for orthogonally retransforming said parallel plurality of orthogonally transformed signal components from said plurality of gain control amplifiers into a serial corrected frame difference signal corresponding to said frame difference signal with said change-induced components removed; mixing means for mixing said corrected frame difference signal with said new frame whereby a noise-reduced video signal is produced; and said frame memory being operative to store said noise-reduced video signal. - View Dependent Claims (28)
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Specification