Statistical mosaics for tracking

A method of robust feature-detection is proposed for visual tracking with a pan-tilt head. Even with good foreground models, the tracking process is liable to be disrupted by strong features in the background. Previous researchers have shown that the disruption can be somewhat suppressed by the use of image-subtraction. Building on this idea, a more powerful statistical model of background intensity is proposed in which a Gaussian mixture distribution is tted to each of the pixels on a \virtual" image plane. A tting algorithm of the \Expectation-Maximisation" type proves to be particularly eeective here. Practical tests with contour tracking show marked improvement over image subtraction methods. Since the burden of computation is oo-line, the online tracking process can run in real-time, at video eld-rate.