Motion compensation method, picture coding method and picture decoding method
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 decoding method comprising:
demultiplexing audio data and video data from multiplexed data in which the audio data and the video data are multiplexed;
decoding the demultiplexed audio data; and
decoding the demultiplexed video data to generate a predictive image of a current block included in a current macroblock of a current picture,
wherein the method further comprises:
obtaining a motion vector of a block for which motion compensation has been performed, the block being included in a co-located block, the co-located block being included in a co-located macroblock, the co-located macroblock being included in a picture different from the current picture, the block being located in a corner of the co-located macroblock;
determining a motion vector of the current block to be “0”, when a size of the obtained motion vector is in a predetermined range;
determining the motion vector of the current block using a motion vector of an adjacent macroblock which is located adjacent to the current macroblock, when the size of the obtained motion vector is beyond the predetermined range; and
performing motion compensation for the current block to generate the predictive image of the current block by using the determined motion vector.
2. The decoding method according to claim 1 , wherein
the predetermined range is a range of −1 to 1.
3. The decoding method according to claim 2 , wherein
the size of the block is smaller than the size of the current block, and
the size of the co-located block is the same as the current block.
4. The decoding method according to claim 3 , wherein
the current macroblock is included in a B picture,
the co-located macroblock is included in the picture subsequent in display order to the current picture, and
the motion vector of the current block is determined using motion vectors of adjacent macroblocks which are located adjacent to the current macroblock when the size of the obtained motion vector is beyond the predetermined range of −1 to 1.
5. The decoding method according to claim 4 ,
wherein a size of the current macroblock and the co-located macroblock is 16 pixels×16 pixels,
a size of the current block is 8 pixels×8 pixels, and
a size of the block is 4 pixels×4 pixels.
6. The decoding method according to claim 5 , wherein
the motion vector of the block located in the corner of the co-located macroblock is obtained when the co-located block comprises a plurality of blocks for which motion compensation has been performed.
7. A decoding apparatus coupled to a memory and comprising processing circuitry, wherein the decoding apparatus, in operation:
demultiplexes audio data and video data from multiplexed data in which audio data and video data are multiplexed;
decodes the demultiplexed audio data; and
decodes the demultiplexed video data to generate a predictive image of a current block included in a current macroblock of a current picture,
wherein the decoding apparatus, in operation, further:
obtains a motion vector of a block for which motion compensation has been performed, the block being included in a co-located block, the co-located block being included in a co-located macroblock, the co-located macroblock being included in a picture different from the current picture, the block being located in the corner of the co-located macroblock;
determines a motion vector of the current block to be “0”, when a size of the obtained motion vector is in a predetermined range;
determines the motion vector of the current block using a motion vector of an adjacent macroblock which is located adjacent to the current macroblock, when the size of the obtained motion vector is beyond the predetermined range; and
performs motion compensation for the current block to generate the predictive image, by using the determined motion vector.
8. The decoding apparatus according to claim 7 , wherein
the predetermined range is a range of −1 to 1.
9. The decoding apparatus according to claim 8 , wherein
the size of the block is smaller than the size of the current block,
the size of the co-located block is the same as the current block.
10. The decoding apparatus according to claim 9 , wherein
the current macroblock is included in a B picture, and
the co-located macroblock is included in the picture subsequent in display order to the current picture, and
the motion vector of the current block is determined using motion vectors of adjacent macroblocks which are located adjacent to the current macroblock when the size of the obtained motion vector is beyond the predetermined range.
11. The decoding apparatus according to claim 10 , wherein
a size of the current macroblock and the co-located macroblock is 16 pixels×16 pixels,
a size of the current block is 8 pixels×8 pixels, and
a size of the block is 4 pixels×4 pixels.
12. The decoding apparatus according to claim 11 , wherein
the decoding apparatus, in operation, obtains the motion vector of the block located in the corner of the co-located macroblock when the co-located block comprises a plurality of blocks for which motion compensation has been performed.