S. Lef` evre, C. Fluck, B. Maillard, N. Vincent : A Fast Snake-based Method to Track Football Players RFAI publication: IAPR International Workshop on Machine Vision Applications, Tokyo (Japan), November 2000, pp. 501–504 A Fast Snake-based Method to Track Football Players S´ ebastien Lef` evre 1,2 , Cyril Fluck 1 , Benjamin Maillard 1 , Nicole Vincent 1 1 Laboratoire d’Informatique E3i / Universit´ e de Tours 64 avenue Portalis, 37200 Tours - FRANCE 2 AtosOrigin 19 rue de la Vall´ ee Maillard BP1311, 41013 Blois Cedex - FRANCE (lefevre,vincent)@univ-tours.fr Abstract We present in this paper a new method to track moving objects. It is based on snakes or active contour models. We are concerned with football game analysis and so the moving objects tracked are representing football players. The camera is moving too. Our active contour algorithm does not need any preprocessing step contrary to most of the snake-based methods. It is based on classical energies used in active contour algorithms but also on a balloon energy in order to reduce the contour to fit the tracked object. The tracking step does not include any position prediction and is based on a snake initialisation followed by snake deformation. The method implemented is fast enough to consider a real-time framework and has been successfully tested on football game image sequences. 1 Introduction Tracking moving humans is a difficult task. We have developed a method that deals with non-rigid moving objects relying on snakes or active contour models. Processing time of our method is very short. This method is applied here to football players tracking. Our snake-based method is performed on a colour image sequence acquired with a moving cam- era. The main contributions of this method are first the use of colour with an active contour model, second the capacity of the method to keep with a moving camera source, and thirdly the absence of any filtering or segmentation before snake deformation in order to decrease processing time. The difficult managing of the variety in texture of the players is counterbalanced by the presence of grassfield. We will first introduce active contour models and then describe the specific energies we have defined for the snake deformation. The tracking method will be next explained and finally some results will be presented and commented. 1