1. A method of operating a computer vision system, the method comprising: receiving a set of vision data at a vision data interface and providing a series of video frames derived from the vision data; constructing from the series of video frames a motion bitmap at a motion detection module; constructing from the series of video frames a foreground bitmap at a background subtraction module; identifying one or more regions within the series of frames each corresponding to an object of a specified category and tracking the one or more regions across multiple frames of the series of video frames by an object tracking module from a comparison of the motion bitmap and foreground bitmap; and from the tracked regions, determining by an object categorizer module of whether each of the identified regions includes an object of the specified category.