Abstract: The invention relates to a conditional replenishment method and apparatus for detecting the most powerfully changed, and for the human eye most important, picture areas in a video image in order to compress the image into a transmission channel which functions at the rates of narrow bandwidth data connections. The digitized picture information read into the video memory is compared to the already transmitted picture information stored in the reference memory, and the change value (M) between these is compared to the preset change threshold (T). If the change value (M) surpasses the change threshold (T), the picture information of the respective picture area is coded and transmitted, and the corresponding picture information is stored into the reference memory, preparatory to a new comparison.