Method, systems and software are proposed for obtaining for blocks of a first image similar blocks of a second image (the “reference image”). The blocks of the first image are processed sequentially, for each block trying out a number of candidate locations in the second image and evaluating a cost function for each. Each candidate location in the second image is displaced by a respective motion vector from the block of the first image. In a first aspect of the invention the cost function is a function of a predicted motion vector for future blocks of the first image (i.e. blocks of the first image which have not yet been processed). In a second aspect of the invention the motion vectors are given by location values which are not all whole pixel spacings, halves of the pixel spacing, or quarters of the pixel spacing.
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