1. Method for coding a sequence of pictures, a picture comprising picture entities, comprising a step for the: calculation of a backward motion vector field of a picture k−s and/or forward motion vector field of a picture k+p, corresponding to a motion estimation of entities respectively of the picture k−s to a following picture k and/or of the picture k+p to a previous picture k, s and p being non-null natural integers, also comprising steps for the: calculation of a rate of use of an entity of the picture k for a backward predictive coding of the picture k−s, according to the number of vectors of the backward motion vector field of the picture k−s pointing to the entity of the picture k or in its near surroundings and/or calculation of a rate of use of an entity of the picture k for a forward predictive coding of the picture k+p, according to the number of vectors of the forward motion vector field of the picture k+p pointing to the entity of the picture k or in its near surroundings, calculation of a rate of picture use for the picture k of the sequence according to the rates of use assigned to the entities of the said picture, calculated for a predictive coding and/or for a future coding, and, this rate of picture use being calculated for other pictures of the picture sequence, also comprising a selection step to select a reference picture for a backward and/or future predictive coding from this reference picture, according to the calculated rates of picture use.