In block-based motion or depth estimation, a block is assigned a motion or depth value as a result of minimizing the matching error over a limited set of candidate values. The matching error for each element of the set is obtained by computing the luminosity differences between a block of a first image (10) and an area of a second image (11). It may occur that an object (12) is partially obstructed by another object (15), so that a pixel (14) in the block is not present in the corresponding area, because another pixel (16) overlaps it. The method and system according to the invention determine which pixels are not visible in the second image (11), and compute the matching error over only the visible pixels. An apparatus for adapting a video signal (40) uses the chosen candidate values to create an enhanced version of the video signal (40).