The present invention relates to a video image processor (1) that is configured to compare (7) a single frame included in the received video signal (3) with a preceding processed frame so as to detect changes. In order to enable the video being compressed in as compact a format as possible the processor (1) is configured to detect (7) changes by dividing the pixels of a single frame into movement blocks and to detect the movement block as changed if in said movement block there is a given number of pixels whose color value change as compared with the corresponding pixels of the preceding processed frame exceeds a predetermined threshold, to exchange (8) the color values of the pixels of the unchanged movement blocks in the frame under process for predetermined values and to generate a signal (4) that indicates the changes.