Patent ID: 8565307

Claim:
A picture encoding method of encoding a picture on a block-by-block basis, said method comprising: deciding a candidate for a prediction method in which a size of motion compensation and a direction of motion prediction are set for a block to be coded; applying motion estimation to the block, by selecting an optimal prediction method using the decided candidate for the prediction method, calculating a motion vector for the block using the selected optimal prediction method, and generating predictive image of the block using the calculated motion vector; and encoding an image of the block using the generated predictive image, wherein said deciding of the candidate for the prediction method includes: (i) determining whether or not the block belongs to a B-picture; (ii) determining, when it is determined that the block belongs to the B-picture, whether or not the size of motion compensation is smaller than a predetermined threshold value; and (iii) setting, as the candidate for the prediction method, only one of a forward direction and a backward direction as the direction of motion prediction when it is determined that the size of motion compensation is smaller than the predetermined threshold value, wherein the size of motion compensation is a size of a part formed by dividing the block into a plurality of parts, and wherein in said applying motion estimation, motion compensation is performed for each of the plurality of parts included in the block to calculate a motion vector for each of the plurality of parts.