Motion compensation method, picture coding method and picture decoding method
View Patent ↗A picture coding apparatus includes a motion vector estimation unit and a motion compensation unit. The motion vector estimation unit selects one method for deriving a motion vector of a block to be motion-compensated, depending on a motion vector of a block located in a corner of a decoded macroblock from among a group of blocks that compose the decoded macroblock corresponding to the current macroblock to be coded and determines the motion vector derived by the selected method for derivation to be a candidate of the motion vector of the current macroblock to be coded. The motion compensation unit generates a predictive image of the block to be motion-compensated based on the estimated motion vector.
1. A motion vector determining method for determining a motion vector of a current block to be coded in direct mode, with reference to a motion vector of an adjacent macroblock that is located adjacent to a current macroblock, the current block being included in the current macroblock and included in a current picture, the motion vector determining method comprising:
specifying, using an adjacent macroblock specifying unit, plural adjacent macroblocks which are located adjacent to the current macroblock;
specifying, using a co-located macroblock specifying unit, a co-located macroblock which is co-located with the current macroblock and included in a picture different from the current picture including the current macroblock;
specifying, using a co-located block specifying unit, a co-located block which is co-located with the current block in the current macroblock and is included in the co-located macroblock, the current block and the co-located block having a size of 8 pixels×8 pixels;
deriving, using a reference motion vector deriving unit, a reference motion vector of the co-located block in the case that a motion compensation of the current block in direct mode is prohibited to a size smaller than 8 pixels×8 pixels;
judging, using a motion vector size judging unit, if a size of the reference motion vector is within a predetermined range;
judging, using a reference picture judging unit, if a reference picture of the current block is located just after the current picture or located just before the current picture; and
determining, using a motion vector determining unit, the motion vector of the current block;
wherein, in the deriving of a reference motion vector, the reference motion vector of the co-located block is derived to be an actual motion vector of a corner block which is included in the co-located block and is located in a corner of the co-located macroblock, and
in the determining of the motion vector of the current block, (1) the motion vector of the current block is determined to be a value of “0” when it is judged in the motion vector size judging step that the reference motion vector is within the predetermined range, and (2) the motion vector of the current block is determined to be a median of plural motion vectors of the plural adjacent macroblocks when it is judged in the motion vector size judging step that the reference motion vector is beyond the predetermined range and it is judged in the reference picture judging step that all reference pictures among a respective reference picture of the plural adjacent macroblocks are located just after the current picture or located just before the current picture.
2. The motion vector determining method according to claim 1 ,
wherein a size of the current macroblock, the adjacent macroblock and the co-located macroblock is 16 pixels×16 pixels,
a size of the current block and the co-located block is 8 pixels×8 pixels, and
a size of the corner block which is included in the co-located block and for which a motion compensation is performed is 4 pixels×4 pixels.
3. A motion vector determining apparatus which determines a motion vector of a current block to be coded in direct mode, with reference to a motion vector of an adjacent macroblock that is located adjacent to a current macroblock, the current block being included in the current macroblock and included in a current picture, the motion vector determining apparatus comprising:
an adjacent macroblock specifying unit operable to specify plural adjacent macroblocks which are located adjacent to the current macroblock;
a co-located macroblock specifying unit operable to specify a co-located macroblock which is co-located with the current macroblock and included in a picture different from the current picture including the current macroblock;
a co-located block specifying unit operable to specify a co-located block which is co-located with the current block in the current macroblock and is included in the co-located macroblock, the current block and the co-located block having a size of 8 pixels×8 pixels;
a reference motion vector deriving unit operable to derive a reference motion vector of the co-located block in the case that a motion compensation of the current block in direct mode is prohibited to a size smaller than 8 pixels×8 pixels;
a motion vector size judging unit operable to judge if a size of the reference motion vector is within a predetermined range;
a reference picture judging unit operable to judge if a reference picture of the current block is located just after the current picture or located just before the current picture; and
a motion vector determining unit operable to determine the motion vector of the current block,
wherein, the reference motion vector deriving unit is operable to derive the reference motion vector of the co-located block to be an actual motion vector of a corner block which is included in the co-located block and is located in a corner of the co-located macroblock, and
the motion vector determining unit is operable to (1) determine the motion vector of the current block to be a value of “0” when it is judged by the motion vector size judging unit that the reference motion vector is within the predetermined range, and (2) determine the motion vector of the current block to be a median of plural motion vectors of the plural adjacent macroblocks when it is judged by the motion vector size judging unit that the reference motion vector is beyond the predetermined range and it is judged by the reference picture judging unit that all reference pictures among a respective reference picture of the plural adjacent macroblocks are located just after the current picture or located just before the current picture.
4. The motion vector determining apparatus according to claim 3 ,
wherein a size of the current macroblock, the adjacent macroblock and the co-located macroblock is 16 pixels×16 pixels,
a size of the current block and the co-located block is 8 pixels×8 pixels, and
a size of the corner block which is included in the co-located block and for which a motion compensation is performed is 4 pixels×4 pixels.