1. A method 101 , in relation to a current video frame 300 comprising a visual element 320 associated with a location in a scene captured in the frame 300 , of matching 140 one of a plurality of mode models 350 to said visual element 320 , said method comprising the steps of: associating said visual element 320 with said plurality of mode models 350 ; and matching 140 one of said plurality of mode models 350 to the visual element 320 , said matching step comprising, for each said mode model 350 , the steps of: determining 420 a visual support value depending upon similarity of corresponding visual characteristics of the visual element 320 and the mode model 350 ; determining 440 a spatial support value depending upon similarity of corresponding temporal characteristics of the mode models 350 associated with the visual element and mode models 385 of one or more other visual elements in the vicinity of said visual element 331 ; and identifying 450 a matching one of said plurality of mode models 350 depending upon the visual support value and the spatial support value.