1. A computer program product stored on a non-transitory computer-readable medium loadable in the memory of at least one computer and including software code portions to implement a method of encoding digital video image sequences including macroblocks by adopting a direct motion-compensated prediction mode based on motion vectors, said prediction mode selected between direct spatial prediction wherein motion vectors for a given macroblock are obtained from motion vectors of macroblocks already encoded within a same image, and direct temporal prediction wherein motion vectors for a given macroblock are obtained from motion vectors of macroblocks of an image previously encoded, the method including: performing a motion estimation of the image sequence subject to encoding, by determining conditions wherein spatial correlation or temporal correlation between subsequent images prevails; adopting, as said motion-compensated prediction mode during encoding, said direct spatial prediction or said direct temporal prediction according to whether said motion estimation indicates that spatial correlation or temporal correlation prevails; subdividing said images in regions by determining, for said regions, respective spatial correlation and temporal correlation indexes; comparing said respective spatial correlation and temporal correlation indexes to identify, for each of said regions, which of said correlation indexes has a higher value; identifying the number of said regions where said spatial correlation index has a higher value and the number of said regions where said temporal correlation index has a higher value; and adopting said direct spatial prediction or said direct temporal prediction according to which is the higher between: the number of said regions where said spatial correlation index has a higher value, or the number of said regions where said temporal correlation index has a higher value.