1. A method of determining motion of a sequence of images, comprising the steps of: partitioning, at a first level, a current image into macroblocks of 2.sup.p .times.2.sup.p pixels and estimating a first motion-vector field associated with said macroblocks at the first level using an iterative and recursive estimation algorithm initialized with motion vectors estimated for a previous image; partitioning, at a second level, each of the macroblocks into quadrants and estimating, for blocks which result therefrom, a second motion-vector field using the same estimation algorithm used for the first level initialized with the vectors which were estimated at the first level; partitioning, at an i.sup.th level, i=3 to p, each of the blocks at level i-1 into quadrants and estimating, for blocks which result therefrom, an i.sup.th motion-vector field using the same estimation algorithm used for the i-1 level initialized with the vectors which were estimated at the i-1 level, a minimum size of the i.sup.th level blocks being no smaller than 2.sup.1 .times.2.sup.1 pixels; determining differences in luminance between the pixels of successive images of corresponding blocks at a highest level of partitioning which are displaced by each of the estimated motion vector fields of the p levels of division; summing, for each of said estimated motion vector fields, said differences in luminance of the pixels within the blocks at the highest level of partitioning; and selecting, for each of said blocks at the highest level of partitioning, a final motion vector field, from said motion vector fields, which has a smallest sum of said differences.