MOTION VECTOR CALCULATION METHOD

摘要

When a block (MB22) of which motion vector is referred to in the direct mode contains a plurality of motion vectors, 2 motion vectors MV23 and MV24, which are used for inter picture prediction of a current picture (P23) to be coded, are determined by scaling a value obtained from averaging the plurality of motion vectors or selecting one of the plurality of the motion vectors.

主权项

1. A picture coding and decoding method which includes a picture coding method for coding a current block included in a current picture in direct mode and a picture decoding method for decoding a current block included in a current picture in direct mode,
wherein the picture coding method comprises: specifying, when a co-located block has two motion vectors, only one motion vector out of the two motion vectors, the co-located block being located in a second picture at the same position that the current block is located in the current picture, the second picture being a B-picture following the current picture in display order; determining a first motion vector and a second motion vector of the current block, using the specified one motion vector; generating a first predictive image of the current block using the first motion vector of the current block and a second predictive image of the current block using the second motion vector of the current block; generating a predictive image of the current block based on the first predictive image and the second predictive image; generating a difference image between the current block and the predictive image of the current block; and coding the difference image to obtain a coded difference image of the current block, wherein, in the case where the co-located block is motion compensated using two motion vectors which refer to a same one reference picture preceding the second picture in display order, one motion vector among the two motion vectors of the co-located block which is output earlier in a bit stream is specified as the only one motion vector of the co-located block in said specifying, and wherein the picture decoding method comprises: specifying, when a co-located block has two motion vectors, only one motion vector out of the two motion vectors, the co-located block being located in a second picture at the same position that the current block is located in the current picture, the second picture being a B-picture following the current picture in display order; determining a first motion vector and a second motion vector of the current block, using the specified one motion vector; generating a first predictive image of the current block using the first motion vector of the current block and a second predictive image of the current block using the second motion vector of the current block; generating a predictive image of the current block based on the first predictive image and the second predictive image; decoding a coded difference image of the current block to obtain a decoded difference image of the current block; and reconstructing the current block by adding the decoded difference image of the current block and the predictive image of the current block, wherein, in the case where the co-located block is motion compensated using two motion vectors which refer to a same one reference picture preceding the second picture in display order, one motion vector among the two motion vectors of the co-located block which appears earlier in a bit stream is specified as the only one motion vector of the co-located block in said specifying.