The invention relates to a detection method applied to digital coded video data available in the form of a video stream comprising consecutive frames divided into macroblocks themselves subdivided into contiguous blocks. These frames comprise I-frames, coded independently, P-frames, predicted from a previous I- or P-frame, and B-frames, bidirectionally predicted from at least two frames between which they are disposed. According to the invention, the processing method comprises the steps of determining for each block of the current frame if it has been coded, or not, according to a predetermined intra prediction mode, collecting similar information for all the blocks of the current frame, for delivering statistics related to said intra prediction mode, analyzing said statistics for determining the number of blocks of said current frame which exhibit, or not, said intra prediction mode, and detecting in the sequence of frames, each time said number is greater than a given threshold, the occurrence of an image, or a sub-region of an image, which is either monochrome or with a repetitive pattern.