Capturing close-up video sequences of an object of interest evolving in a large field of view often requires to cover this field of view with tens of cameras. This is especially the case in surveillance and sport coverage contexts. The use of Pan-Tilt-Zoom cameras allows zooming and focusing on an object along its displacement with a single camera, but requires a sufficiently reliable feedback about the target position/trajectory from the image processing module in order to perform high quality automatic tracking.
Tracking can be defined as recursively matching an object of interest between two successive frames of a video sequence. We propose an original framework for solving this matching problem using a set of points to describe the target. Modeling an object with points allows dealing with zoom changes, which is difficult with a global object appearance model. In our formulation, the target displacement inference error is minimized regarding the choice of points to match and their associated matching metrics, i.e. the associated (descriptor, matching distance) pair. There are major differences with classical point matching approaches :
: Quentin De Neyer, Christophe De Vleeschouwer, A resource allocation framework for adaptive selection of point matching strategies, ACIVS 2013, Poznan, Poland -> to be published
A simplified closed-loop control system involving the motorized camera and the image processing (point-based tracking) module is depicted on the figure below. The feedback is given by the detected position of the target, the setpoint being the center of the camera field of view. We use a PI controller and test the system with an original method by projecting pre-recorded videos on a screen. The system then tracks the projected object of interest. This allows to perform reproducible and well controlled tests.
The principal tasks for setting up a PTZ control systems are :
Our system was demonstrated during the International Conference on Distributed Smart Cameras (ICDSC) in 2012.
: De Neyer, Q.; Sun, L.; Chaudy, C.; Parisot, C.; De Vleeschouwer, C., "Demo: Point matching for PTZ camera autotracking,", 2012 Sixth International Conference on Distributed Smart Cameras (ICDSC), vol., no., pp.1,2, Oct. 30 2012-Nov. 2 2012 PDF
Last updated September 19, 2017, at 12:11 PM