Encoder, decoder, encoding method, and decoding method
An encoder includes: circuitry; and memory, in which using the memory, the circuitry, in affine motion compensation prediction in inter prediction for a current block, places a limit on a range within which motion estimation or motion compensation is performed, and performs the motion compensation for the current block.
1. An encoder comprising:
circuitry; and
memory, wherein
using the memory, the circuitry,
in affine motion compensation prediction in inter prediction for a current block, places a limit on a range within which motion estimation or motion compensation is performed, and performs the motion compensation for the current block, and
the limit on the range within which the motion estimation or the motion compensation is performed is placed so that a variation between a control point motion vector at a top left corner and a control point motion vector at a top right corner of the current block in the affine motion compensation prediction falls within a predetermined range.
2. The encoder according to claim 1 , wherein
in the affine motion compensation prediction,
the limit on the range within which the motion estimation or the motion compensation is performed is newly determined for each current picture, or an appropriate set is selected for each current picture from among a plurality of predetermined sets of motion estimation ranges or a plurality of predetermined sets of motion compensation ranges.
3. The encoder according to claim 1 , wherein
in the affine motion compensation prediction,
the limit on the range within which the motion, estimation or the motion compensation is performed is changed in accordance with a type of a reference picture.
4. The encoder according to claim 1 , wherein
in the affine motion compensation prediction,
the limit on the range within which the motion estimation or the motion compensation is performed is determined for each predetermined profile and level.
5. The encoder according to claim 1 , wherein
in the affine motion compensation prediction,
the limit on the range within which the motion estimation or the motion compensation is performed is determined in accordance with motion-estimation processing power depending on computational processing power on an encoder side or memory bandwidth.
6. The encoder according to claim 1 , wherein
in the affine motion compensation prediction,
the limit on the range within which the motion estimation or the motion compensation is performed includes a limit on reference pictures in addition to a limit on a range of referable pixels.
7. The encoder according to claim 1 , wherein
in the affine motion compensation prediction,
information about the limit on the range within which the motion estimation or the motion compensation is performed is included in header information of a video parameter set (VPS), a sequence parameter set (SPS), or a picture parameter set (PPS) of an encoded bitstream.
8. The encoder according to claim 1 , wherein
in the affine motion compensation prediction,
the information about the limit on the range within which the motion estimation or the motion compensation is performed includes information for limiting reference pictures in addition to information for limiting a range of referable pixels.
9. The encoder according to claim 1 , wherein
in the affine motion compensation prediction,
in the motion estimation for affine inter mode, when a region referred to by a motion vector derived from a current control point motion vector to be evaluated is outside the range within which the motion estimation is performed, the current control point motion vector is eliminated from candidates on which the motion estimation is performed.
10. The encoder according to claim 1 , wherein
in the affine motion compensation prediction,
in affine inter mode, when a region referred to by a motion vector derived from a control point motion vector predictor obtained from surrounding encoded blocks neighboring the current block is outside the range within which the motion estimation is performed, encoding is prevented from being performed in the affine inter mode.
11. The encoder according to claim 1 , wherein
in the affine motion compensation prediction,
in affine merge mode, when a region referred to by a motion vector derived from a control point motion vector obtained from surrounding encoded blocks neighboring the current block is outside the range within which the motion compensation is performed, encoding is prevented from being performed in the affine merge mode.
12. A decoder comprising:
circuitry; and
memory, wherein
using the memory, the circuitry,
in affine motion compensation prediction in inter prediction for a current block, places a limit on a range within which motion estimation or motion compensation is performed, and performs the motion compensation for the current block to decode an encoded stream, and
the limit on the range within which the motion estimation or the motion compensation is performed is placed so that a variation between a control point motion vector at a top left corner and a control point motion vector at a top right corner of the current block in the affine motion compensation prediction falls within a predetermined range.
13. The decoder according to claim 12 , wherein
in the affine motion compensation prediction,
the limit on the range within which the motion estimation or the motion compensation is performed is newly determined for each current picture, or an appropriate set is selected for each current picture from among a plurality of predetermined sets of motion estimation ranges or a plurality of predetermined sets of motion compensation ranges.
14. The decoder according to claim 12 , wherein
in the affine motion compensation prediction,
the limit on the range within which the motion estimation or the motion compensation is performed is changed in accordance with a type of a reference picture.
15. The decoder according to claim 12 , wherein
in the affine motion compensation prediction,
the limit on the range within which the motion estimation or the motion compensation is performed is determined for each predetermined profile and level.
16. The decoder according to claim 12 , wherein
in the affine motion compensation prediction,
the limit on the range within which the motion estimation or the motion compensation is performed is determined in accordance with motion-estimation processing power depending on computational processing power on an encoder side or memory bandwidth.
17. The decoder according to claim 12 , wherein
in the affine motion compensation prediction,
the limit on the range within which the motion estimation or the motion compensation is performed includes a limit on reference pictures in addition to a limit on a range of referable pixels.
18. The decoder according to claim 12 , wherein
in the affine motion compensation prediction,
information about the limit on the range within which the motion estimation or the motion compensation is performed is included in header information of a video parameter set (VPS), a sequence parameter set (SPS), or a picture parameter set (PPS) of an encoded bitstream.
19. The decoder according to claim 12 , wherein
in the affine motion compensation prediction,
the information about the limit on the range within which the motion estimation or the motion compensation is performed includes information for limiting reference pictures in addition to information for limiting a range of referable pixels.
20. The decoder according to claim 12 , wherein
in the affine motion compensation prediction,
in the motion estimation for affine inter mode, when a region referred to by a motion vector derived from a current control point motion vector to be evaluated is outside the range within which the motion estimation is performed, the current control point motion vector is eliminated from candidates on which the motion estimation is performed.
21. The decoder according to claim 12 , wherein
in the affine motion compensation prediction,
in affine inter mode, when a region referred to by a motion vector derived from a control point motion vector predictor obtained from surrounding decoded blocks neighboring the current block is outside the range within which the motion estimation is performed, encoding is prevented from being performed in the affine inter mode.
22. The decoder according to claim 12 , wherein
in the affine motion compensation prediction,
in affine merge mode, when a region referred to by a motion vector derived from a control point motion vector obtained from surrounding decoded blocks neighboring the current, block is outside the range within which the motion compensation is performed, encoding is prevented from being performed in the affine merge mode.
23. An encoding method comprising:
in affine motion compensation prediction in inter prediction for a current block, placing a limit on a range within which motion estimation or motion compensation is performed, and performing the motion compensation for the current block, wherein
the limit on the range within which the motion estimation or the motion compensation is performed is placed so that a variation between a control point motion vector at a top left corner and a control point motion vector at a top right corner of the current block in the affine motion compensation prediction falls within a predetermined range.
24. A decoding method comprising:
in affine motion compensation prediction in inter prediction for a current block, placing a limit on a range within which motion estimation or motion compensation is performed, and performing the motion compensation for the current block to decode an encoded stream, wherein
the limit on the range within which the motion estimation or the motion compensation is performed is placed so that a variation between a control point motion vector at a top left corner and a control point motion vector at a top right corner of the current block in the affine motion compensation prediction falls within a predetermined range.