Encoder, decoder, encoding method, and decoding method
View Patent ↗An encoder includes circuitry and memory. Using the memory, the circuitry: in an inter prediction mode in which an affine motion vector is calculated for each of sub-blocks constituting a current block of a picture in the video, based on motion vectors of neighboring blocks of the current block, changes a shape or size of the sub-block according to a variation in direction or variation in magnitude among the motion vectors of the neighboring blocks; calculates the affine motion vector for the sub-block having the shape or size changed; and performs the motion compensation for the sub-block having the shape or size changed.
1. An encoder that encodes a video by motion compensation, the encoder comprising:
circuitry; and
memory,
wherein, using the memory, the circuitry:
in an inter prediction mode in which an affine motion vector is calculated for each of sub-blocks constituting a current block of a picture in the video, based on motion vectors of neighboring blocks of the current block,
changes a shape or size of the sub-block when a variation in direction or variation in magnitude among motion vectors of control points in the current block satisfies a predetermined condition, the motion vectors of the control points being derived based on the motion vectors of the neighboring blocks;
calculates the affine motion vector for the sub-block having the shape or size changed; and
performs the motion compensation for the sub-block having the shape or size changed,
wherein the circuitry selects a horizontally long or vertically long sub-block as the shape or size of the sub-block when the variation in direction or variation in magnitude among the motion vectors of the control points satisfies the predetermined condition.
2. The encoder according to claim 1 ,
wherein the predetermined condition is defined by a relationship between (i) a threshold value and (ii) a variation in horizontal component and a variation in vertical component among the motion vectors of the control points.
3. A decoder that decodes a video by motion compensation, the decoder comprising:
circuitry; and
memory,
wherein, using the memory, the circuitry:
in an inter prediction mode in which an affine motion vector is calculated for each of sub-blocks constituting a current block of a picture in the video, based on motion vectors of neighboring blocks of the current block,
changes a shape or size of the sub-block when a variation in direction or variation in magnitude among motion vectors of control points in the current block satisfies a predetermined condition, the motion vectors of the control points being derived based on the motion vectors of the neighboring blocks;
calculates the affine motion vector for the sub-block having the shape or size changed; and
performs the motion compensation for the sub-block having the shape or size changed,
wherein the circuitry selects a horizontally long or vertically long sub-block as the shape or size of the sub-block when the variation in direction or variation in magnitude among the motion vectors of the control points satisfies the predetermined condition.
4. The decoder according to claim 3 ,
wherein the predetermined condition is defined by a relationship between (i) a threshold value and (ii) a variation in horizontal component and a variation in vertical component among the motion vectors of the control points.
5. An encoding method of encoding a video by motion compensation, the encoding method comprising:
in an inter prediction mode in which an affine motion vector is calculated for each of sub-blocks constituting a current block of a picture in the video, based on motion vectors of neighboring blocks of the current block,
changing a shape or size of the sub-block when a variation in direction or variation in magnitude among motion vectors of control points in the current block satisfies a predetermined condition, the motion vectors of the control points being derived based on the motion vectors of the neighboring blocks;
calculating the affine motion vector for the sub-block having the shape or size changed; and
performing the motion compensation for the sub-block having the shape or size changed,
wherein a horizontally long or vertically long sub-block is selected as the shape or size of the sub-block when the variation in direction or variation in magnitude among the motion vectors of the control points satisfies the predetermined condition.
6. A decoding method of decoding a video by motion compensation, the decoding method comprising:
in an inter prediction mode in which an affine motion vector is calculated for each of sub-blocks constituting a current block of a picture in the video, based on motion vectors of neighboring blocks of the current block,
changing a shape or size of the sub-block when a variation in direction or variation in magnitude among motion vectors of control points in the current block satisfies a predetermined condition, the motion vectors of the control points being derived based on the motion vectors of the neighboring blocks;
calculating the affine motion vector for the sub-block having the shape or size changed; and
performing the motion compensation for the sub-block having the shape or size changed,
wherein a horizontally long or vertically long sub-block is selected as the shape or size of the sub-block when the variation in direction or variation in magnitude among the motion vectors of the control points satisfies the predetermined condition.
7. The encoder according to claim 1 ,
wherein when the variation in direction or variation in magnitude among the motion vectors of the control points satisfies the predetermined condition, the size of the sub-block is changed to a size larger than the smallest size.
8. The encoder according to claim 7 ,
wherein the smallest size is 4×4.
9. The encoder according to claim 7 ,
wherein the size larger than the smallest size is 8×8.
10. The encoder according to claim 7 ,
wherein the predetermined condition is a condition that the motion vectors of the control points in the current block are non-directional.
11. The encoder according to claim 7 ,
wherein the predetermined condition is a condition that the magnitude of the motion vectors of the control points in the current block is less than or equal to a threshold value.
12. The decoder according to claim 3 ,
wherein when the variation in direction or variation in magnitude among the motion vectors of the control points satisfies the predetermined condition, the size of the sub-block is changed to a size larger than the smallest size.
13. The decoder according to claim 12 ,
wherein the smallest size is 4×4.
14. The decoder according to claim 12 ,
wherein the size larger than the smallest size is 8×8.
15. The decoder according to claim 12 ,
wherein the predetermined condition is a condition that the motion vectors of the control points in the current block are non-directional.
16. The decoder according to claim 12 ,
wherein the predetermined condition is a condition that the magnitude of the motion vectors of the control points in the current block is less than or equal to a threshold value.
17. The encoding method according to claim 5 ,
wherein when the variation in direction or variation in magnitude among the motion vectors of the control points satisfies the predetermined condition, the size of the sub-block is changed to a size larger than the smallest size.
18. The encoding method according to claim 17 ,
wherein the smallest size is 4×4.
19. The encoding method according to claim 17 ,
wherein the size larger than the smallest size is 8×8.
20. The encoding method according to claim 17 ,
wherein the predetermined condition is a condition that the motion vectors of the control points in the current block are non-directional.
21. The encoding method according to claim 17 ,
wherein the predetermined condition is a condition that the magnitude of the motion vectors of the control points in the current block is less than or equal to a threshold value.
22. The decoding method according to claim 6 ,
wherein when the variation in direction or variation in magnitude among the motion vectors of the control points satisfies the predetermined condition, the size of the sub-block is changed to a size larger than the smallest size.
23. The decoding method according to claim 22 ,
wherein the smallest size is 4×4.
24. The decoding method according to claim 22 ,
wherein the size larger than the smallest size is 8×8.
25. The decoding method according to claim 22 ,
wherein the predetermined condition is a condition that the motion vectors of the control points in the current block are non-directional.
26. The decoding method according to claim 22 ,
wherein the predetermined condition is a condition that the magnitude of the motion vectors of the control points in the current block is less than or equal to a threshold value.