Moving picture coding method, moving picture decoding method, moving picture coding apparatus, moving picture decoding apparatus, and moving picture coding and decoding apparatus
A moving picture coding method includes: coding, using a motion vector, a current block to be coded; generating a plurality of predictive motion vectors; and coding the motion vector using one of the predictive motion vectors, and when a co-located block included in a coded picture and co-located with the current block has two reference motion vectors and reference directions of the two reference motion vectors are the same, a first prediction vector is generated using a first reference motion vector and a second prediction vector is generated using a second reference motion vector in the generating of a plurality of predictive motion vectors.
1. A moving picture coding method of coding a current block which is included in a current picture by performing temporal prediction using a co-located block which is included in a coded picture, the co-located block having two reference motion vectors, the two reference motion vectors being two motion vectors calculated with reference to one or more pictures located before the current picture in display order, said moving picture coding method comprising:
coding the current block using a first motion vector and a second motion vector, respectively, with reference to a first reference picture list and a second reference picture list;
generating a first predictive motion vector and a second predictive motion vector; and
coding the first motion vector and the second motion vector, respectively, using the first predictive motion vector and the second predictive motion vector, wherein
(i) when any reference pictures in the first reference picture list and the second reference picture list are located before the current picture in display order,
the first predictive motion vector is generated using a first reference motion vector out of the two reference motion vectors, the first predictive motion vector and the first reference motion vector each corresponding to the first reference picture list, and
the second predictive motion vector is generated using a second reference motion vector out of the two reference motion vectors, the second predictive motion vector and the second reference motion vector each corresponding to the second reference picture list, the second reference motion vector being different than the first reference motion vector, and
(ii) when a reference picture in the first reference picture list and the second reference picture list are not located before the current picture in display order, and the first reference motion vector and the second reference motion vector refer to different directions,
both of the first predictive motion vector and the second predictive motion vector are generated using only one of the first reference motion vector and the second reference motion vector.
2. A moving picture coding apparatus which codes a current block which is included in a current picture by performing temporal prediction using a co-located block which is included in a coded picture, the co-located block having two reference motion vectors, the two reference motion vectors being two motion vectors calculated with reference to one or more pictures located before the current picture in display order, said moving picture coding apparatus comprising:
at least one image processor; and
storage coupled to the at least one processor;
wherein the at least one processor:
codes the current block using a first motion vector and a second motion vector, respectively, with reference to a first reference picture list and a second reference picture list;
generates a first predictive motion vector and a second predictive motion vector; and
codes the first motion vector and the second motion vector, respectively, using the first predictive motion vector and the second predictive motion vector, wherein
(i) when any reference pictures in the first reference picture list and the second reference picture list are located before the current picture in display order,
the first predictive motion vector is generated using a first reference motion vector out of the two reference motion vectors, the first predictive motion vector and the first reference motion vector each corresponding to the first reference picture list, and
the second predictive motion vector is generated using a second reference motion vector out of the two reference motion vectors, the second predictive motion vector and the second reference motion vector each corresponding to the second reference picture list, the second reference motion vector being different than the first reference motion vector, and
(ii) when a reference picture in the first reference picture list and the second reference picture list are not located before the current picture in display order, and the first reference motion vector and the second reference motion vector refer to different directions,
both of the first predictive motion vector and the second predictive motion vector are generated using only one of the first reference motion vector and the second reference motion vector.