Method and apparatus for tracking moving objects in real time using contours of the objects and feature paths
First Claim
1. A method for tracking, in real time, a moving object represented by a video signal comprised of prior frames and a current frame and having an object image with features associated with the object, said method comprising the steps of:
- matching a select feature path defined by x and y component values representing motion of the features of an object with a candidate cluster defined by x and y component values chosen from a plurality of preexisting clusters representing motion of the object, said select feature path having a portion concurrent in time with some of the clusters in said plurality of clusters, said candidate cluster selected as the cluster closest in distance to the select feature path, the distance being calculated according to a function having a first component and a second component, the first component being representative of a maximum displacement between the select feature path and the candidate cluster, and the second component being representative of differences between velocity vectors defining motion of the select feature path and velocity vectors defining motion of the candidate cluster wherein the select feature path is comprised of path points, wherein the candidate cluster is comprised of cluster points, and wherein the second component of the distance function is computed according to the following formula;
##EQU11## wherein P represents the select path, Z represents the candidate cluster, 1 represents the overlap length between P and Z, and wherein represents a first instant of overlap between the select path P and the candidate cluster Z.
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Abstract
A method and apparatus for tracking moving objects, such as people, in real time by grouping existing feature paths from a current video frame with preexisting clusters from current video frames. Grouping is accomplished by selecting, as a candidate cluster to a specified feature path, the cluster having the closest relative distance to the specified feature path. The relative distance is calculated according to a function having a first component and a second component. The first component is representative of a maximum displacement between the select feature path and the candidate cluster, and the second component is representative of the difference between velocity vectors defining the select feature path motion and velocity vectors defining the candidate cluster motion. The method and apparatus also provide for updating the candidate cluster with parameters obtained from the select feature path and for merging overlapping clusters.
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Citations
12 Claims
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1. A method for tracking, in real time, a moving object represented by a video signal comprised of prior frames and a current frame and having an object image with features associated with the object, said method comprising the steps of:
matching a select feature path defined by x and y component values representing motion of the features of an object with a candidate cluster defined by x and y component values chosen from a plurality of preexisting clusters representing motion of the object, said select feature path having a portion concurrent in time with some of the clusters in said plurality of clusters, said candidate cluster selected as the cluster closest in distance to the select feature path, the distance being calculated according to a function having a first component and a second component, the first component being representative of a maximum displacement between the select feature path and the candidate cluster, and the second component being representative of differences between velocity vectors defining motion of the select feature path and velocity vectors defining motion of the candidate cluster wherein the select feature path is comprised of path points, wherein the candidate cluster is comprised of cluster points, and wherein the second component of the distance function is computed according to the following formula;
##EQU11## wherein P represents the select path, Z represents the candidate cluster, 1 represents the overlap length between P and Z, and wherein represents a first instant of overlap between the select path P and the candidate cluster Z.- View Dependent Claims (2)
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3. A method for tracking, in real time, a moving object represented by a video signal comprised of prior frames and a current frame and having an object image with features associated with the object, said method comprising the steps of:
matching a select feature path defined by x and y component values presenting motion of the features of an object with a candidate cluster defined by x and y component values chosen from a plurality of preexisting clusters representing motion of the object, said select feature path having a portion concurrent in time with some of the clusters in said plurality of clusters, said candidate cluster selected as the cluster closest in distance to the select feature path, the distance being calculated according to a function having a first component and a second component, the first component being representative of a maximum displacement between the select feature path and the candidate cluster, and the second component being representative of differences between velocity vectors defining motion of the select feature path and velocity vectors defining motion of the candidate cluster, wherein the select feature path is comprised of path points, wherein the candidate cluster is comprised of cluster points, and wherein the second component of the distance function is computed according to the following formula;
##EQU14## wherein P represents the select path, Z represents the candidate cluster, 1 represents the overlap length between P and Z, and wherein Pt.sbsb.a =Zt.sbsb.r represents a first instant of overlap between the select path P and the candidate cluster Z.- View Dependent Claims (4, 5)
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6. A method for tracking, in real time, a moving object represented by a video signal derived from prior frames and a current frame, the video signal having an object image and a background image, the object image having a bounding contour with extrema of curvature, said method comprising the steps of:
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(a) isolating, from the current frame, the object image from the background image; (b) detecting the bounding contour of the isolated object image and the extrema of curvature of the bounding contour; (c) identifying a plurality of points on the detected bounding contour, some points in said plurality defined as feature points corresponding to a location of a feature of the object and represented by the extrema of curvature, each point in said plurality having coordinates associated therewith; (d) comparing the coordinates of some of said identified points of the object image of the current frame with coordinates of corresponding previously identified points of an object image of an immediately preceding frame for correlating at least some of said current identified points with said corresponding ones of said previously identified points, each of said previously identified points having a previously defined feature path associated therewith, each feature path having components representing motion of said feature paths; (e) assigning at least some of said identified points to a select one of the previously identified feature paths based on the comparison from said comparing step, and updating the components of the select feature path with the components of the associated points; (f) updating parameters of a select one of a plurality of preexisting clusters, at least one of which represents motion of the moving object, with the components of the updated select feature path if the updated select feature path is associated with the select cluster; and (g) selecting a candidate cluster from said plurality of preexisting clusters if said updated select feature path is not associated with any of said preexisting clusters, and updating the parameters of the candidate cluster with the components of the select path, the candidate cluster being chosen based on a smallest distance value of a distance calculation between the select path and each of the preexisting clusters in said plurality of preexisting clusters. - View Dependent Claims (7, 8, 9)
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10. A device for tracking, in real time, a moving object represented by a video signal derived from prior frames and a current frame, the video signal having an object image and a background image, the object image having a bounding contour with extrema of curvature, said device comprising:
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means for isolating, from the current frame, the object image from the background image; means for detecting the bounding contour of the isolated object image and the extrema of curvature of the bounding contour; means for identifying a plurality of points on the detected bounding contour, some points in said plurality defined as feature points corresponding to the location of a feature of the object and represented by the extrema of curvature, each point in said plurality having coordinates associated therewith; means for comparing the coordinates of some of said identified points of the object image of the current frame with coordinates of corresponding previously identified points of an object image of an immediately preceding frame for correlating at least some of said current identified points with said corresponding ones of said previously identified points, each of said previously identified points having a previously defined feature path associated therewith, each feature path having components representing motion of said feature paths; means for assigning at least some of said identified points to a select one of the previously identified feature paths and updating the components of the select feature path with the components of the associated points; means for updating parameters of a select one of a plurality of preexisting clusters, at least one of which representing motion of the moving object, with the components of the select feature path if the select path is associated with the select cluster; and means for selecting a candidate cluster if said updated select path is not associated with the select cluster, and updating parameters of the candidate cluster with the components of the select path, the candidate cluster being chosen based on a smallest distance value of a distance calculation between the select path and each cluster in the plurality of preexisting clusters. - View Dependent Claims (11, 12)
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Specification