1. A method of processing data representing pixels of a video frame, the pixels having been pre-classified as belonging either to a foreground or background region, the method comprising: (a) identifying, in the video frame, a region that includes two or more adjacent foreground pixels; (b) identifying, in the video frame, one or more foreground pixels as being candidates for re-classification by means of using a predetermined algorithm; (c) re-classifying the candidate pixels as background pixels and generating a comparison frame including said re-classified pixels; (d) identifying, from the comparison frame, foreground pixels whose respective frame position is within the region identified in step (a); and (e) classifying foreground pixels identified in step (d) as representing a common foreground object.