1. A motion estimation method performed by a processor for a succession of frames in a digital coding system, comprising the following steps: a) with reference to a first block in a first frame, searching within at least a portion of a second frame for a second block that corresponds to the first block; and b) estimating, using the processor, a motion vector of the first block with respect to the second block in at least the portion of the second frame; wherein step a) includes: calculating weighted distances of candidate blocks from a candidate origin block in the second frame based on the following equation: 
 weighted distance= H ( u, v ), where H is a predetermined weighted distance function, u is a U-axis coordinate distance of the candidate block from the candidate origin block, and v is a V-axis coordinate distance of the candidate block from the candidate origin block, the U-axis and V-axis constituting bases of a plane; and searching the second frame in an increasing order of the calculated weighted distances of the candidate blocks, starting from a candidate origin block.