Target tracking
First Claim
1. A method of tracking a target imaged in video footage, the method comprising the steps of:
- (i) identifying the target to be tracked in a first image frame, the target being located at a first position;
(ii) defining a first template area around the first position;
(iii) generating a first population of sub-templates by sampling from the first template area;
(iv) searching for an instance of each of the first population of sub-templates in a second image frame, and determining the location of each instance in the second image frame;
(v) determining a second position of the target in the second image frame in dependence on the locations of the instances;
(vi) selecting a selection of the first population of sub-templates in dependence on the locations of the instances of each of the sub-templates in the second frame;
(vii) defining a second template area defined around the second position;
(viii) generating a second population of sub-templates comprising the selection of the first population of sub-templates, and a set of new sub-templates generated by sampling from the second template area; and
(ix) iterating steps (iv) to (viii) above in respect of further image frames, using the second population of sub-templates and the second position from a preceding iteration in place of the first population of sub-templates and the first position, thereby determining a series of target positions, and inferring the target track therefrom,wherein the step of identifying a second position of the target comprises the step of determining a permitted area, and constraining the second position to lie within the permitted area, andwherein the step of searching for an instance of each of the first population of sub-templates in a second image frame includes searching areas of the second image frame outside the permitted area.
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Accused Products
Abstract
A method and system are disclosed for tracking a target imaged in video footage. The target may, for example, be a person moving through a crowd The method comprises the steps of: identifying a target in a first frame; generating a population of sub-templates by sampling from a template area defined around the target position; and searching for instances of the sub-templates in a second frame so as to locate the target in the second frame. Sub-templates whose instances are not consistent with the new target position are removed from the population and replaced by newly sampled sub-templates. The method can then be repeated so as to find the target in further frames. It can be implemented in a system comprising video imaging means, such as a CCTV camera, and processing means operable to carry out the method.
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Citations
16 Claims
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1. A method of tracking a target imaged in video footage, the method comprising the steps of:
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(i) identifying the target to be tracked in a first image frame, the target being located at a first position; (ii) defining a first template area around the first position; (iii) generating a first population of sub-templates by sampling from the first template area; (iv) searching for an instance of each of the first population of sub-templates in a second image frame, and determining the location of each instance in the second image frame; (v) determining a second position of the target in the second image frame in dependence on the locations of the instances; (vi) selecting a selection of the first population of sub-templates in dependence on the locations of the instances of each of the sub-templates in the second frame; (vii) defining a second template area defined around the second position; (viii) generating a second population of sub-templates comprising the selection of the first population of sub-templates, and a set of new sub-templates generated by sampling from the second template area; and (ix) iterating steps (iv) to (viii) above in respect of further image frames, using the second population of sub-templates and the second position from a preceding iteration in place of the first population of sub-templates and the first position, thereby determining a series of target positions, and inferring the target track therefrom, wherein the step of identifying a second position of the target comprises the step of determining a permitted area, and constraining the second position to lie within the permitted area, and wherein the step of searching for an instance of each of the first population of sub-templates in a second image frame includes searching areas of the second image frame outside the permitted area. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A tracking system comprising imaging means operable to generate video footage, and processing means operable to carry out a method of tracking a target imaged in video footage, the method comprising the steps of:
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(i) identifying the target to be tracked in a first image frame, the target being located at a first position; (ii) defining a first template area around the first position; (iii) generating a first population of sub-templates by sampling from the first template area; (iv) searching for an instance of each of the first population of sub-templates in a second image frame, and determining the location of each instance in the second image frame; (v) determining a second position of the target in the second image frame in dependence on the locations of the instances; (vi) selecting a selection of the first population of sub-templates in dependence on the locations of the instances of each of the sub-templates in the second frame; (vii) defining a second template area defined around the second position; (viii) generating a second population of sub-templates comprising the selection of the first population of sub-templates, and a set of new sub-templates generated by sampling from the second template area; and (ix) iterating steps (iv) to (viii) above in respect of further image frames, using the second population of sub-templates and the second position from a preceding iteration in place of the first population of sub-templates and the first position, thereby determining a series of target positions, and inferring the target track therefrom, wherein the step of identifying a second position of the target comprises the step of determining a permitted area, and constraining the second position to lie within the permitted area, and wherein the step of searching for an instance of each of the first population of sub-templates in a second image frame includes searching areas of the second image frame outside the permitted area.
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16. A non-transitory computer readable medium having recorded thereon a computer program product operable, when the computer readable medium is inserted into a computer, to cause the computer to execute a method of tracking a target imaged in video footage, the method comprising the steps of:
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(i) identifying the target to be tracked in a first image frame, the target being located at a first position; (ii) defining a first template area around the first position; (iii) generating a first population of sub-templates by sampling from the first template area; (iv) searching for an instance of each of the first population of sub-templates in a second image frame, and determining the location of each instance in the second image frame; (v) determining a second position of the target in the second image frame in dependence on the locations of the instances; (vi) selecting a selection of the first population of sub-templates in dependence on the locations of the instances of each of the sub-templates in the second frame; (vii) defining a second template area defined around the second position; (viii) generating a second population of sub-templates comprising the selection of the first population of sub-templates, and a set of new sub-templates generated by sampling from the second template area; and (ix) (iv) to (viii) above in respect of further image frames, using the second population of sub-templates and the second position from a preceding iteration in place of the first population of sub-templates and the first position, thereby determining a series of target positions, and inferring the target track therefrom, wherein the step of identifying a second position of the target comprises the step of determining a permitted area, and constraining the second position to lie within the permitted area, and wherein the step of searching for an instance of each of the first population of sub-templates in a second image frame includes searching areas of the second image frame outside the permitted area.
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Specification