1. A method of detecting an opaque image in an area of each of a sequence of frames comprising pixels that represent digital video images, comprising the steps of: detecting a scene change between at least two of said frames, designated as a current frame and a reference frame; upon detecting a scene change, calculating a stochastic measure σ d of a plurality of pixels in the image frame based on the standard deviation of differences in pixel values in said two frames in the temporal domain; and detecting an opaque image in said area by comparing the stochastic measure σ d with a given noise level (STD).