Acquiring a current image from an inputted video and a background model which comprises a background image and foreground/background classification information of visual elements; classifying the visual elements in the current image as foreground or background; determining similarity measures between the current image and groups in the background model, wherein visual elements in the current image are the visual elements in the current image which are classified as the foreground, wherein visual elements in the groups in the background model are the visual elements whose classification information is the foreground, and wherein the visual elements in the groups in the background model are the visual elements which neighbour to corresponding portions of the visual elements in the groups in the current image; and identifying whether the visual elements in the current image which are classified as the foreground are falsely classified or not according to the determined similarity measures.