Video signal noise reduction system using time-varying filter coefficients
First Claim
1. Apparatus for reducing noise in an input video signal which includes a plurality of video frames, the apparatus comprising:
- processed frame memory means for storing a noise reduced image;
motion estimator means for selecting a target block of image components in said frame memory to be used in calculating a noise reduced video signal; and
motion compensated noise reduction means for calculating said noise reduced video signal by calculating a set of time-varying weighted filtering coefficients for the target block and for generating a motion block of noise reduced image components by averaging a plurality of image components in a current block selected from the video signal with respective image components of the target block as weighted by the coefficients.
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Abstract
A video signal noise reduction system is disclosed in which corresponding image pixels from a current frame and image pixels from a noise reduced previous frame are averaged to produce respective noise reduced pixel values. In the disclosed exemplary embodiment of the invention, a processed frame memory stores a noise reduced image and a motion estimator identifies a target block of pixels in this processed frame memory to be used in calculating a noise reduced video signal. A motion compensated noise reduction processor combines the block of the noise reduced image pixels stored in the processed frame memory with a current block of pixels generated from the video signal to produce a motion block of noise reduced pixels. The relative weighting applied to the stored pixel and the current pixel depends on the number of pixels that were used to generate the stored pixel. A breakdown detector discards pixels in the motion block if a measure of noise reduction achieved for the one component divided by a measure of noise in the motion block is greater than a threshold value. Sparkle reduction is used to replace any original component of the motion block with its corresponding noise reduced component if all of the components adjacent to the original component have been replaced by their corresponding noise reduced components.
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Citations
13 Claims
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1. Apparatus for reducing noise in an input video signal which includes a plurality of video frames, the apparatus comprising:
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processed frame memory means for storing a noise reduced image; motion estimator means for selecting a target block of image components in said frame memory to be used in calculating a noise reduced video signal; and motion compensated noise reduction means for calculating said noise reduced video signal by calculating a set of time-varying weighted filtering coefficients for the target block and for generating a motion block of noise reduced image components by averaging a plurality of image components in a current block selected from the video signal with respective image components of the target block as weighted by the coefficients.
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2. Apparatus for reducing noise in an input video signal which includes a plurality of video frames, the apparatus comprising:
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processed frame memory means for storing a noise reduced image; motion estimator means for identifying a target block of image components in said frame memory to be used in calculating a noise reduced video signal; motion compensated noise reduction means for calculating said noise reduced video signal by calculating a set of time-varying weighted filtering coefficients for the target block and for generating a motion block of noise reduced image components by averaging a plurality of image components in a current block selected from the video signal with respective image components of the target block as weighted by the coefficients; and breakdown detection means for replacing each one image component of the current block with a corresponding noise-reduced image component of the motion block if a measure of noise reduction achieved for the one image component divided by a reference measure of noise is less than a threshold value. - View Dependent Claims (3, 4)
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5. Apparatus for reducing noise in an input video signal which includes a plurality of video frames, the apparatus comprising:
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processed frame memory means for storing a noise reduced image; motion estimator means for identifying a target block of image components in said frame memory to be used in calculating a noise reduced video signal; motion compensated noise reduction means for calculating said noise reduced video signal by calculating a set of time-varying weighted filtering coefficients for the target block and for generating a motion block of noise reduced image components by averaging a plurality of image components in a current block selected from the video signal with respective image components of the target block as weighted by the coefficients; and classification means for determining a measure of variation which occurs in the current block and for calculating a weighting value and a threshold value to be used by the motion estimator means.
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6. Apparatus for reducing noise in an input video signal which includes a plurality of video frames, the apparatus comprising:
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processed frame memory means for storing a noise reduced image; motion estimator means for identifying a target block of image components in said frame memory to be used in calculating a noise reduced video signal; motion compensated noise reduction means for calculating said noise reduced video signal by calculating a set of time-varying weighted filtering coefficients for the target block and for generating a motion block of noise reduced image components by averaging a plurality of image components in a current block selected from the video signal with respective image components of the target block as weighted by the coefficients; and means for providing a plurality of trial velocity vectors to the motion estimator means for use in identifying the target block.
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7. Apparatus for reducing noise in an input video signal which includes a plurality of video frames, the apparatus comprising:
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processed frame memory means for storing a noise reduced image; motion estimator means for identifying a target block of image components in said frame memory to be used in calculating a noise reduced video signal; motion compensated noise reduction means for calculating said noise reduced video signal by calculating a set of time-varying weighted filtering coefficients for the target block and for generating a motion block of noise reduced image components by averaging a plurality of image components in a current block selected from the video signal with respective image components of the target block as weighted by the coefficients; and future frame memory means for holding image components representing an image which is to be displayed following the current image, wherein the motion estimator means includes means for identifying a further block of image components in said future frame memory means and the motion compensated noise reduction means includes means for generating said motion block of image components by combining the current block of image components with at least one of the target block of image components and the further target block of image components.
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8. A method of reducing noise in a video signal which includes a plurality of video frames, the method comprising the steps of:
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storing a noise reduced image in processed frame memory; selecting a target block of picture elements in said processed frame memory to be used in calculating a noise reduced video signal; and calculating said noise reduced video signal by combining the block of the noise reduced image pixels stored in the processed frame memory with a current block of pixels generated from the video signal and calculating a set of time-varying weighted filtering coefficients for the target block and for generating a motion block of noise reduced pixels by averaging the plurality of pixels in the block of noise reduced image pixels with respective pixels of the current block of pixels as weighted by the coefficients.
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9. A method of reducing noise in a video signal which includes a plurality of video frames, the method comprising the steps of:
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storing a noise reduced image in a processed frame memory; identifying a target block of picture elements in said processed frame memory to be used in calculating a noise reduced video signal; and calculating said noise reduced video signal by combining the block of the noise reduced image pixels stored in the processed frame memory with a current block of pixels generated from the video signal and calculating a set of time-varying weighted filtering coefficients for the target block and for generating a motion block of noise reduced pixels by averaging the plurality of pixels in the block of noise reduced image pixels of the current block of pixels as weighted by the coefficients; and replacing each one of the pixels of the current block with a corresponding noise-reduced pixel from the motion block if a measure of noise reduction achieved for the one pixel divided by a measure of noise in the video signal is less than a threshold value. - View Dependent Claims (10, 11, 12, 13)
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Specification