| 摘要 |
A method for determining a motion vector is provided to improve overall coding efficiency by differently determining the direct mode forward and backward motion vectors of a B(Bi-predictive) picture according to a reference buffer that a motion vector, produced from a specific picture, indicates and making direct mode frequently used as coding mode in coding B pictures. In decoding the current image block, a decoder acquires reference picture information. Based on the acquired reference picture information, the decoder determines at least one reference picture of the current image block from a plurality of pictures stored in a reference buffer. In this case, the reference picture information indicates a reference picture type which is based on the temporal distance between the current picture and a reference picture. The decoder acquires motion vectors of a co-located image block. Based on the acquired motion vectors and the reference picture type, the decoder creates one or more motion vectors of the current image block. The decoder decodes the current image block by judging the movement of the current image block using the created motion vectors.
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