1. A method of processing compressed digital data derived from an original sequence of images, the digital data organized as a set of image frames, each image frame including a set of blocks, each block including a string of bits corresponding to an area of an image frame of the original sequence of images, comprising the steps of: counting a number of bits for sets of at least one of said strings of bits in the compressed digital data; deriving a cost function for each set of strings, said cost function being a number related to the number of bits in each set of strings of bits; applying a temporal segmentation technique to the cost functions associated with strings of bits pertaining to at least two image frames represented in said compressed digital data; identifying at least one image frame from said compressed digital data.