Method of tracking scene motion for live video insertion systems
First Claim
1. A method for tracking motion from field to field with sub-pixel precision in a sequence of related video images having odd and even interlaced fields, the method comprising the steps of:
- a) establishing an array of idealized x and y coordinates representing a reference array having a plurality of landmarks where each landmark has unique x and y coordinates;
b) detecting the positions x and y of the visible sub-set of the reference array landmarks in the current image;
c) predicting the location, x'"'"' and y'"'"', of said visible sub-set of landmarks in the next video field with sub-pixel precision by using the detected positions of said landmark in the current and the two preceding video fields,wherein prediction errors due to interlace differences in the video images are minimized without creating two separate streams of prediction data, by using the position of the landmark found in the previous video field and adding to that the difference vector equal to the measured difference in said landmark'"'"'s position in the current field and said landmark'"'"'s position in the video two fields ago; and
,d. mapping x and y coordinates in a current image to said x and y coordinates in said reference array using a calculated difference between the predicted location of the visible sub-set of landmarks in the current field, which was predicted in step (c) from the previous video field, and the detected positions of corresponding landmarks of the visible sub-set in the current field to thereby weight each detected landmark'"'"'s contribution to the mapping function.
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Abstract
A method for tracking motion from field to field in a sequence of related video broadcast images. The method uses template correlation to follow a set of predetermined landmarks within a scene in order to provide position information of objects in the current image. The current image object position information is compared to position information of the same objects within a reference array data table. The comparison is accomplished through the use of warp equations that map points in the current image to points in the reference array. Motion is tracked according to a velocity prediction scheme utilizing a weighted formula that emphasizes the weight of landmarks that are closer to their predicted position.
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Citations
24 Claims
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1. A method for tracking motion from field to field with sub-pixel precision in a sequence of related video images having odd and even interlaced fields, the method comprising the steps of:
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a) establishing an array of idealized x and y coordinates representing a reference array having a plurality of landmarks where each landmark has unique x and y coordinates; b) detecting the positions x and y of the visible sub-set of the reference array landmarks in the current image; c) predicting the location, x'"'"' and y'"'"', of said visible sub-set of landmarks in the next video field with sub-pixel precision by using the detected positions of said landmark in the current and the two preceding video fields, wherein prediction errors due to interlace differences in the video images are minimized without creating two separate streams of prediction data, by using the position of the landmark found in the previous video field and adding to that the difference vector equal to the measured difference in said landmark'"'"'s position in the current field and said landmark'"'"'s position in the video two fields ago; and
,d. mapping x and y coordinates in a current image to said x and y coordinates in said reference array using a calculated difference between the predicted location of the visible sub-set of landmarks in the current field, which was predicted in step (c) from the previous video field, and the detected positions of corresponding landmarks of the visible sub-set in the current field to thereby weight each detected landmark'"'"'s contribution to the mapping function.
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2. A system for tracking motion from field to field with sub-pixel precision in a sequence of related video images having odd and even interlaced fields comprising:
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a) scanning means for establishing an array of idealized x and y coordinates representing a reference array having a plurality of landmarks where each landmark has unique x and y coordinates; b) detecting means for detecting the positions x and y of the visible sub-set of the reference array landmarks in the current image; c) predicting means for predicting the location, x'"'"' and y'"'"', of said visible sub-set of landmarks in the next video field with sub-pixel precision by using the detected positions of said landmark in the current and the two preceding video fields, wherein prediction errors due to interlace differences in the video images are minimized without creating two separate streams of prediction data, by using the position of the landmark found in the previous video field and adding to that the difference vector equal to the measured difference in said landmark'"'"'s position in the current field and said landmark'"'"'s position in the video two fields ago; and
,d. mapping means for mapping x and y coordinates in a current image to said x and y coordinates in said reference array using a calculated difference between the predicted location of the visible sub-set of landmarks in the current field, which was predicted in step (c) from the previous video field, and the detected positions of corresponding landmarks of the visible sub-set in the current field to thereby weight each detected landmark'"'"'s contribution to the mapping function.
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3. A method for tracking motion from field to field in a sequence of related video images having odd and even interlaced fields, the method comprising the steps of:
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a) establishing an array of idealized x and y coordinates representing a reference array having a plurality of landmarks where each landmark has unique x and y coordinates; b) mapping x and y coordinates in a current image to said x and y coordinates in said reference array, where said mapping is achieved according to the following relationships;
space="preserve" listing-type="equation">x'"'"'=a+bx+cy
space="preserve" listing-type="equation">y'"'"'=d+ex+fywhere; x is a horizontal coordinate in the reference array, y is a vertical coordinate in the reference array, x'"'"' is a horizontal coordinate in the current scene, y'"'"' is a vertical coordinate in the current scene, a is a warp parameter for horizontal translation of the object in the x direction, b is a warp parameter for magnification between the reference array and the current image in the x direction, c is a warp parameter for a combination of rotation and skew in the x direction, d is a warp parameter for vertical translation of the object in the y direction, e is a warp parameter for a combination of rotation and skew in the y direction, and f is a warp parameter for magnification between the reference array and the current image in the y direction; and
,c) predicting the future location of said landmark coordinates, x'"'"' and y'"'"', based on a detected change of position of said landmark from the previous field, wherein prediction errors due to interlace differences in the video images are minimized by using the position of the landmark found in the previous video field adjusted by the difference in position of the same landmark in the two preceding fields. - View Dependent Claims (4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A method for tracking motion from field to field in a sequence of related video images having odd and even interlaced fields, the method comprising the steps of:
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a) establishing an array of idealized x and y coordinates representing a reference array having a plurality of landmarks where each landmark has unique x and y coordinates; b) mapping x and y coordinates in a current image to said x and y coordinates in said reference array, where said mapping is achieved according to the following relationships;
space="preserve" listing-type="equation">x'"'"'=a+bx
space="preserve" listing-type="equation">y'"'"'=d+bywhere; x is a horizontal coordinate in the reference array, y is a vertical coordinate in the reference array, x'"'"' is a horizontal coordinate in the current scene, y'"'"' is a vertical coordinate in the current scene, a is a warp parameter for horizontal translation of the object in the x direction, b is a warp parameter for magnification between the reference array and the current image, and, d is a warp parameter for vertical translation of the object in the y direction; and
,c) predicting the future location of said landmark coordinates, x'"'"' and y'"'"', based on a detected change of position of said landmark from the previous field, wherein prediction errors due to interlace differences in the video images are minimized by using the position of the landmark found in the previous video field adjusted by the difference in position of the same landmark in the two preceding fields.
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18. A system for tracking motion from field to field in a sequence of related video images having like and unlike interlaced fields comprising:
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scanning means for establishing an array of idealized x and y coordinates representing a reference array having a plurality of landmarks where each landmark has unique x and y coordinates; mapping means for mapping x and y coordinates in a current image to said x and y coordinates in said reference array; and
,predicting means for predicting the future location of said landmark coordinates, x'"'"' and y'"'"', based on a detected change of position of said landmark from the previous field, wherein prediction errors due to interlace differences in the video images are minimized by using the position of the landmark found in the previous video field adjusted by the difference in position of the same landmark in the two preceding fields; and
,searching means for searching for one of said landmarks in said current image with a correlation template substantially centered at the predicted location of said landmark wherein said search is performed beginning from said predicted location and proceeding outward looking for a match and discontinued when said match exceeds a threshold value. - View Dependent Claims (19, 20, 21, 22, 23, 24)
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Specification