1. A computer program product 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, and 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.