SYSTEM AND METHOD FOR VIDEO-BASED DETERMINATION OF QUEUE CONFIGURATION PARAMETERS

• US 20150312529A1
• Filed: 04/24/2014
• Published: 10/29/2015
• Est. Priority Date: 04/24/2014
• Status: Active Grant

• Current Assignee: Conduent Business Services, LLC (Conduent, Inc.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Bernal, Edgar A., Li, Qun, Loce, Robert P.
• Granted Patent: US 9,846,811 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06T 2207/10016 Video; Image sequence
• CPC Class Codes: G06T 2207/30236 Traffic on road, railway or crossing
• CPC Class Codes: G06T 2207/30241 Trajectory
• CPC Class Codes: G06T 7/246 using feature-based methods, e.g. the tracking of corners or segments
• CPC Class Codes: G06V 20/52 Surveillance or monitoring of activities, e.g. for recognising suspicious objects recognising microscopic objects G06V20/69
• CPC Class Codes: G06V 20/54 of traffic, e.g. cars on the road, trains or boats

Abstract

A method for automatically determining a dynamic queue configuration includes acquiring a series of frames from an image source surveying a queue area. The method includes detecting at least one subject in a frame. The method includes tracking locations of each detected subject across the series of frames. The method includes generating calibrated tracking data by mapping the tracking locations to a predefined coordinate system. The method includes localizing a queue configuration descriptor based on the tracking data.

Claims

1. A method for automatically determining a dynamic queue configuration, the method comprising:

acquiring a series of frames from an image source surveying a queue area;

detecting at least one subject in a frame;

tracking locations of each detected subject across the series of frames; and

,

estimating a queue configuration descriptor based on the tracking data.

2. The method of claim 1, wherein the tracking locations of each detected subject includes:

generating spatio-temporal information describing the locations of the each subject in pixel coordinates as a function of time.

3. The method of claim 1 further comprising:

performing a geometric transformation on the tracking data by converting the pixel coordinates to one of real-world coordinates, a coordinate system of a camera in the image source, and a reference coordinate system.

4. The method of claim 3 further comprising:

in response to the tracking data being acquired from at least two image sources, mapping coordinate systems of each individual image source into a common coordinate system.

5. The method of claim 1 further comprising:

classifying an occupancy in the queue area into one of at least two predetermined levels.

6. The method of claim 5, wherein the classifying includes:

computing a metric corresponding to the queue occupancy;

comparing the metric to a predetermined threshold;

in response to the metric not meeting the threshold, classifying the occupancy in the queue area as belonging to a first predetermined level; and

,

in response to the metric meeting and exceeding the threshold, classifying the occupancy in the queue area as belonging to a second predetermined level.

7. The method of claim 6 further comprising:

in response to the occupancy being classified as belonging to the first predetermined level, employing a variable pipeline latency approach to localize the queue configuration descriptor; and

,

in response to the occupancy being classified as belonging to the second predetermined level, employing a constant pipeline latency approach to localize the queue configuration descriptor.

8. The method of claim 1, wherein the estimating the queue configuration descriptor includes:

determining a start point where a queue forms in at least one of the series of frames;

identifying at least one subject located near the start point in a select frame;

backtracking the locations of the at least one subject in the series of frames from the start point; and

,

generating a mapping of the locations of the at least one subject across the series of frames; and

,

fitting a primitive descriptor to the set of locations generated by the mapping; and

associating the fitted primitive descriptors as the queue configuration descriptor.

9. The method of claim 1, wherein the estimating the queue configuration descriptor includes:

tracking sequences of points across a predetermined number of frames using the tracking data of the each subject to generate a set of trajectories, each trajectory corresponding to a subject;

initializing clusters of trajectories by placing a cluster seed at a location corresponding to each start point where a queue forms;

processing at least one trajectory relative to the clusters of trajectories, the trajectory currently unassigned to a cluster, the processing including;

computing a distance between the clusters of trajectories and the tracking points of the trajectory being processed,

in response to the computed distance not meeting and exceeding a predetermined threshold, adding the trajectory to the cluster to which the trajectory is closest according to the computed distance,

in response to the computed distance meeting and exceeding a predetermined threshold, discarding the trajectory, and

repeating the computing until no trajectories remain to be processed;

fitting a primitive descriptor to sets of trajectories belonging to each resulting cluster; and

,

associating the fitted primitive descriptors as the queue configuration descriptor.

10. The method of claim 9, wherein the assigning the each trajectory to the at least one cluster includes:

computing a Mahalanobis distance (x_i−

x_j)^TΣ

<sup>−

1</sup>(x_i−

x_j) between a centroid of a last trajectory added to a cluster, x_i and an unassigned candidate trajectory x_j, wherein a covariance estimate Σ

is given by a sample covariance of the last trajectory added to the candidate cluster.

11. The method of claim 1, further comprising:

extracting at least one queue-related parameter from the queue configuration descriptor; and

,

providing the queue-related parameter as output.

12. A system for automatically determining a dynamic queue configuration, the system comprising a device for monitoring queue dynamics including a memory in communication with a processor configured to:

acquire a series of frames from an image source surveying a queue area;

detect at least one subject in a frame;

track locations of each detected subject across the series of frames; and

,

estimate a queue configuration descriptor based on the tracking data.

13. The system of claim 12, wherein the processor is further configured to:

generate spatio-temporal information describing the locations of the each subject in pixel coordinates as a function of time.

14. The system of claim 12, wherein the processor is further configured to:

perform a geometric transformation on the tracking data by converting the pixel coordinates to one of real-world coordinates, a coordinate system of a camera in the image source, and a reference coordinate system.

15. The system of claim 14, wherein the processor is further configured to:

in response to the tracking data being acquired from at least two image sources, map coordinate systems of each individual image source into a common coordinate system.

16. The system of claim 12, wherein the processor is further configured to:

classify an occupancy in the queue area into one of at least two predetermined levels.

17. The system of claim 16, wherein the processor is further configured to:

compute a metric corresponding to the occupancy;

compare the metric to a predetermined threshold;

in response to the metric not meeting the threshold, classify the occupancy in the queue area as belonging to a first predetermined level; and

,

in response to the metric meeting and exceeding the threshold, classify the occupancy in the queue area as belonging to a second predetermined level.

18. The system of claim 17, wherein the processor is further configured to:

in response to the occupancy being classified as belonging to the first predetermined level, employ a pipeline latency approach to localize the queue configuration descriptor; and

,

in response to the occupancy being classified as belonging to the second predetermined level, employ a constant pipeline latency approach to localize the queue configuration descriptor.

19. The system of claim 12, wherein the processor is further configured to:

determine a start point where a queue forms in at least one of the series of frames;

identify at least one subject located near the start point in a select frame;

backtrack the locations of the at least one subject in the series of frames from the start point; and

,

generate a mapping of the locations of the at least one subject across the series of frames; and

,

fit a primitive descriptor to the set of locations generated by the mapping; and

associate the fitted primitive descriptors as the queue configuration descriptor.

20. The system of claim 12, wherein the processor is further configured to:

track sequences of points across a predetermined number of frames using the tracking data of the each subject to generate a set of trajectories, each trajectory corresponding to a subject;

initialize clusters of trajectories by placing a cluster seed at a location corresponding to each start point where a queue forms;

process at least one trajectory relative to the clusters of trajectories, the trajectory currently unassigned to a cluster, the processing including;

compute a distance between the clusters of trajectories and the tracking points of the trajectory being processed,

in response to the computed distance not meeting and exceeding a predetermined threshold, add the trajectory to the cluster to which the trajectory is closest according to the computed distance,

in response to the computed distance meeting and exceeding a predetermined threshold, discard the trajectory, and

repeat the computing until no trajectories remain to be processed;

fit a primitive descriptor to sets of trajectories belonging to each resulting cluster; and

,

associate the fitted primitive descriptors as the queue configuration descriptor.

21. The system of claim 20, wherein the assigning the each trajectory to the at least one cluster includes:

compute a Mahalanobis distance (x_i−

x₁)^TΣ

<sup>−

1</sup>(x_i−

x_j) between a centroid of a last trajectory added to a cluster, x_i and an unassigned candidate trajectory x_j, wherein a covariance estimate Σ

is given by a sample covariance of the last trajectory added to the candidate cluster.

22. The system of claim 12, wherein the processor is further adapted to:

extract at least one queue-related parameter from the queue configuration descriptor; and

,

provide the queue-related parameter as output.