Motion stabilization
First Claim
Patent Images
1. A method of digital image stabilization, comprising the steps of:
- providing a low-resolution version of an input digital picture;
partitioning said low-resolution version into reliable blocks and unreliable blocks according to motion prediction errors;
aggregating said reliable blocks into candidate motion regions according to block motion vectors for said reliable blocks;
finding a segmentation of said low-resolution version from said candidate motion regions, wherein said finding a segmentation includes comparing scores for said candidate motion regions where said score for a region includes a difference of an average relative block motion from a maximum, a measure of the number of said reliable blocks in a region, and a measure of the number of said reliable blocks in a region which are also in a segmentation for a low-resolution version of a prior picture;
updating said segmentation to a segmentation of said input picture;
finding a global motion vector for said input picture from said segmentation of said input picture; and
compensating for jitter motion in said input picture using said global motion vector.
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Abstract
Stabilization for devices such as hand-held camcorders segments a low-resolution frame into a region of reliable estimation, refines the motion vectors of that region hierarchically while at the same time updating the segmentation, finds a global motion vector for the region at high resolution, and uses the global motion vector to compensate for jitter.
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Citations
7 Claims
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1. A method of digital image stabilization, comprising the steps of:
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providing a low-resolution version of an input digital picture; partitioning said low-resolution version into reliable blocks and unreliable blocks according to motion prediction errors; aggregating said reliable blocks into candidate motion regions according to block motion vectors for said reliable blocks; finding a segmentation of said low-resolution version from said candidate motion regions, wherein said finding a segmentation includes comparing scores for said candidate motion regions where said score for a region includes a difference of an average relative block motion from a maximum, a measure of the number of said reliable blocks in a region, and a measure of the number of said reliable blocks in a region which are also in a segmentation for a low-resolution version of a prior picture; updating said segmentation to a segmentation of said input picture; finding a global motion vector for said input picture from said segmentation of said input picture; and compensating for jitter motion in said input picture using said global motion vector. - View Dependent Claims (2)
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3. A method of jitter compensation for video frames, comprising the steps of:
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providing a resolution hierarchy, F1, F2, . . . FN, for an input frame with N an integer greater than 2 and said input frame equal to FN; partitioning said F1 into blocks plus border regions; for each of said blocks, (i) computing a block motion vector, (ii) computing prediction errors for said block motion vector and for motion vectors differing by 1 from said block motion vector, and (iii) when a sum of differences of said prediction errors exceeds a first threshold, designating said each of said blocks as a reliable block; aggregating said reliable blocks into candidate motion regions according to block motion vectors for said reliable blocks; selecting a segmentation for F1 from said candidate motion regions by comparing said regions according to (i) the number of blocks, (ii) the number of blocks corresponding to blocks in a segmentation of a hierarchy of a prior frame, and (iii) an average of relative block motion vectors, wherein said segmentation comprises comparing scores for candidate motion regions where said score for a region includes a difference of an average relative block motion from a maximum, a measure of the number of said reliable blocks in a region, and a measure of the number of said reliable blocks in a region which are also in a segmentation for a low-resolution version of a prior picture; for n=2, . . . , N, selecting a segmentation for Fn by repeating the above steps for blocks corresponding to blocks of said segmentation of Fn−
1;computing a global motion vector from said segmentation of FN; and using said global motion vector to jitter compensate said input frame. - View Dependent Claims (4, 5, 6)
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7. A video camera, comprising:
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picture capturer; a jitter estimator coupled to said picture capturer, said jitter estimator including; a resolution hierarchy downsampler; a segmenter coupled to said downsampler, said segmenter operable to sequentially find a segmentation plus motion vector for each level of a resolution hierarchy computed from an input picture, wherein said segmentation comprises comparing scores for candidate motion regions where said score for a region includes a difference of an average relative block motion from a maximum, a measure of the number of said reliable blocks in a region, and a measure of the number of said reliable blocks in a region which are also in a segmentation for a low-resolution version of a prior picture; a global motion vector determiner coupled to said segmenter; a memory for a resolution hierarchy of a prior frame, said memory coupled to said jitter estimator; and jitter motion compensater coupled to said jitter estimator.
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Specification