Object Tracker for Visually Tracking Object Motion
First Claim
1. An object tracker comprising:
- a sampling unit which generates particles based on an estimated existence probability distribution of a target object in a first image frame, the particles being used for a particle filter in a parameter space where target candidates are defined, the first image frame being contained in a video stream together with a second image frame;
a plurality of model tracking units which correspond respectively to multiple motion models and observe likelihoods of the target candidates with respect to the target object in the second image frame, the target candidates being defined by the particles transited according to each motion model; and
a tracking integration unit which chooses one of the motion models based on a comparison of the likelihoods observed by the model tracking units, and estimates an existence probability distribution of the target object in the second image frame based on the likelihood of a target candidate which is defined according to the motion model chosen.
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Accused Products
Abstract
A tracking start-and-stop determining unit of a tracking processing unit determines whether to start or stop tracking based on a predetermined condition. During tracking, a sampling unit 29 creates or eliminates particles using a probability density distribution estimated for the previous image frame. A first to nth model tracking units transit the particles according to motion models respectively assigned, and observe the likelihood of a candidate curve corresponding to each particle with respect to an edge image generated by an image processing unit. A tracking integration unit determines a motion model which causes the highest likelihood, and estimates a probability density distribution using an observation likelihood based on the motion model.
104 Citations
14 Claims
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1. An object tracker comprising:
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a sampling unit which generates particles based on an estimated existence probability distribution of a target object in a first image frame, the particles being used for a particle filter in a parameter space where target candidates are defined, the first image frame being contained in a video stream together with a second image frame;
a plurality of model tracking units which correspond respectively to multiple motion models and observe likelihoods of the target candidates with respect to the target object in the second image frame, the target candidates being defined by the particles transited according to each motion model; and
a tracking integration unit which chooses one of the motion models based on a comparison of the likelihoods observed by the model tracking units, and estimates an existence probability distribution of the target object in the second image frame based on the likelihood of a target candidate which is defined according to the motion model chosen. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. An object tracking method performed by a computer, the method comprising:
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storing a received video stream in a memory;
reading a first image frame in the video stream from the memory, and calculating amounts of changes of a target object using multiple hypothetical motion models from an existence probability distribution of the target object in the first image frame;
comparing temporary characteristics of the target object specified by the amounts of changes calculated with true characteristics of the target object in a second image frame read from the memory, and choosing a motion model describing the temporary characteristics with the highest likelihood from the multiple hypothetical motion models based on the result of comparison; and
estimating an existence probability distribution of the target object in the second image frame based on the chosen motion model.
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14. A computer program product causing a computer to perform an object tracking, comprising:
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a program code module for storing a received video stream in a memory;
a program code module for reading a first image frame in the video stream from the memory, and calculating amounts of changes of a target object using multiple hypothetical motion models from an existence probability distribution of the target object in the first image frame;
a program code module for comparing temporary characteristics of the target object specified by the amounts of changes calculated with true characteristics of the target object in a second image frame read from the memory, and choosing a motion model describing the temporary characteristics with the highest likelihood from the multiple hypothetical motion models based on a result of comparison; and
a program code module for estimating an existence probability distribution of the target object in the second image frame based on the chosen motion model.
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Specification