1. A method of tracking an object in a video stream comprising a plurality of video frames, the method comprising: (a) running an object detector, on a computer, at a plurality of sampling locations, the locations defining a first grid spaced across a first video frame, and recording a hit, to electronic storage, at each location where an object of interest is found; and (b) running the object detector, on the computer, at a further plurality of sampling locations defining a second grid spaced across a succeeding second video frame, the second grid being offset from the first grid, wherein larger points, which have a size of at least 2×2 points of a fine grained grid, cover the entire first grid and the entire second grid and wherein each of the larger points has one of the sampling locations of the first grid and one of the further sampling locations of the second grid and wherein each of the further sampling locations is offset with respect to a corresponding sampling location of the first grid for a respective larger point and simultaneously running the detector employing parallel processing, on the computer, in addition at one or more further locations on the second frame derived from each location on the first frame at which a hit was recorded.