Method for efficiently storing the trajectory of tracked objects in video
First Claim
1. A method for storing a trajectory of tracked objects in a video, comprising the steps of:
- (a) identifying objects in a first video frame;
(b) determining first reference coordinates (xrefi,yrefi) for each of said objects identified in step (a) in the first video frame;
(c) storing the first reference coordinates (xrefi,yrefi);
(d) identifying said objects in a second video frame;
(e) determining current reference coordinates (xnewiynewi) of said objects in said second video frame; and
(f) storing the current reference coordinates of a particular object in an object trajectory list and replacing the first reference coordinates (xrefi,yrefi) with the current reference coordinates (xnewiynewi) if the following condition for the particular object is satisfied;
∥
(xnewi,ynewi)−
(xrefi,yrefi)∥
2≧
ε
,
wherein ε
is a predetermined threshold amount, and retaining the first reference coordinates (xrefi,yrefi) for comparison with subsequent video frames when said condition is not satisfied.
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Abstract
A process and system for enhanced storage of trajectories reduces storage requirements over conventional methods and systems. A video content analysis module automatically identifies objects in a video frame, and determines the (xi,yi) coordinates of each object i. The reference coordinates for each for object i, (xrefi,yrefi) are set to (xi,yi) when the object is first identified. For subsequent frames, if the new coordinates (xnewi,ynewi) are less than a given distance from the reference coordinates, that is if ∥(xnewi,ynewi)−(xref1,yrefi)∥2<ε, then the current coordinates are ignored. However, if the object moves more than the distance ε, the current coordinates (xnewi,ynewi) are stored in the object'"'"'s trajectory list, and we set the reference coordinates (xref1,yrefi) to the object'"'"'s current position. This process is repeated for all subsequent video frames. The resulting compact trajectory lists can then be written to memory or disk while they are being generated, or when they are complete.
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Citations
25 Claims
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1. A method for storing a trajectory of tracked objects in a video, comprising the steps of:
-
(a) identifying objects in a first video frame;
(b) determining first reference coordinates (xrefi,yrefi) for each of said objects identified in step (a) in the first video frame;
(c) storing the first reference coordinates (xrefi,yrefi);
(d) identifying said objects in a second video frame;
(e) determining current reference coordinates (xnewiynewi) of said objects in said second video frame; and
(f) storing the current reference coordinates of a particular object in an object trajectory list and replacing the first reference coordinates (xrefi,yrefi) with the current reference coordinates (xnewiynewi) if the following condition for the particular object is satisfied;
∥
(xnewi,ynewi)−
(xrefi,yrefi)∥
2≧
ε
,
wherein ε
is a predetermined threshold amount, andretaining the first reference coordinates (xrefi,yrefi) for comparison with subsequent video frames when said condition is not satisfied. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. A system for storage of the trajectory of tracked objects in a video, comprising:
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a processor;
a video input for providing images to the processor;
a video content analysis module for tracking coordinates of objects in the images provided to the processor; and
means for storage of object trajectories;
wherein the video content module assigns a reference coordinate value to each object identified in a first reference frame of the images, and updates the reference coordinate value to a value of a subsequent frame only when an amount of motion of the object in the subsequent frame relative to the first frame exceeds a threshold from the reference coordinate value. - View Dependent Claims (20, 21, 22, 23, 24)
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25. A method for storing a trajectory of tracked objects in a video, comprising the steps of:
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(a) identifying objects in a first video frame;
(b) determining first reference coordinates (xrefi,yrefi) for each of said objects identified in step (a) in the first video frame;
(c) storing the first reference coordinates (xrefi,yrefi);
(d) identifying said objects in a second video frame;
(e) determining current reference coordinates (xnewiynewi) of said objects in said second video frame; and
(f) storing the current reference coordinates of a particular object in an object trajectory list and replacing the first reference coordinates (xrefi,yrefi) with the current reference coordinates (xnewiynewi) if the following condition for the particular object is satisfied;
|xnewi−
xrefi|+|ynewi−
yrefi≧
ε
;
wherein ε
is a predetermined threshold amount, andretaining the first reference coordinates (xrefi,yrefi) for comparison with subsequent video frames when said condition is not satisfied.
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Specification