1. A method for encoding a sequence of images, comprising: implementing a prediction of least one block of a current image of the sequence from a block of a reference image pre-divided into blocks, said prediction associating at least one block of a current image of said sequence with at least one corresponding block in at least one intermediate image time-localized between said reference image and said current image, to be forward motion-compensated, said intermediate image or images having been previously encoded, a phase of optimized partitioning delivering a common partitioning of at least one given block of said reference image, comprising the following steps: determining a first plurality of motion vectors, called control vectors-associated in the current image with several characteristic points of said given block, said control vectors each representing a shift between a characteristic point of said given block of the reference image and a corresponding position of said characteristic point in the current image, dividing said given block into sub-blocks in taking account of said first plurality of control vectors defining a first partition, determining a second plurality of motion vectors, called control vectors associated in the intermediate image, each representing a shift between a characteristic point of said given block of the reference image and a corresponding position of said characteristic point in the intermediate image, dividing said given block in sub-blocks in taking account of said second plurality of control vectors, defining a second partition, obtaining said common partitioning into sub-blocks for said given block, called basic sub-blocks, by union of said first and second partitions, a phase for predicting said current image from said intermediate image obtained preliminarily from said reference image to which said common partitioning into basic sub-blocks for said given block has been applied, said prediction phase comprising the following steps: determining a first set of modified control vectors for said basic sub-blocks from the control vectors associated with the block of current image, determining a second set of modified control vectors for said basic sub-blocks from control vectors associated with the intermediate image forward motion-compensating a basic sub-block shifted in motion by means of said second set of modified control vectors delivering a sub-block of said intermediate image, forward motion-compensating said sub-block of said intermediate image towards a corresponding sub-block of said current image by means of said first set of control vectors.