Motion vector prediction in video encoding and decoding
A video codec can involve encoding and decoding picture information and first and second flags, wherein the encoding or decoding of the picture information is based on a coding mode indicated by the first flag or the second flag, and the first flag indicates a subblock merge mode and the second flag indicates an inter affine prediction mode, and the encoding or decoding of the first flag uses Context-Based Adaptive Binary Arithmetic Coding (CABAC) based on a first probability model and encoding or decoding of the second flag uses CABAC based on a second probability model.
1 . A method comprising:
decoding a first flag included in a bitstream, the first flag being associated with picture information, and the first flag having been encoded using a first Context-Based Arithmetic Coding (CABAC);
decoding a second flag included in the bitstream, the second flag being associated with the picture information, and the second flag having been encoded using a second CABAC separate from the first CABAC; and
decoding at least a portion of the picture information included in the bitstream based on a coding mode indicated by the first flag or the second flag, wherein:
the first flag indicates whether or not a temporal mode is used, wherein in the temporal mode a temporal merge list is constructed that comprises only temporal motion predictor candidates; and
the second flag indicates whether or not an affine prediction mode is used.
2 . The method of claim 1 , wherein:
the affine prediction mode indicates use of an affine motion compensation, and
the temporal merge list comprises a subblock temporal motion vector prediction mode which derives motion information for subblocks of a block from motion information in a reference picture of a picture to which the block belongs.
3 . The method of claim 1 , wherein the temporal merge list comprises at least one of:
a subblock temporal motion vector prediction mode;
a temporal motion vector prediction mode;
a combined inter and intra prediction mode based on a temporal motion vector predictor;
a triangle prediction mode based on a temporal motion vector predictor; or
a merge motion vector difference prediction mode based on a temporal motion vector predictor.
4 . The method of claim 1 , wherein the temporal merge list is placed at one of the following positions in a block decoding process: as a first merge list, after a regular merge list, after an affine merge list, after a combined inter and intra prediction merge list, or after a triangle merge list.
5 . The method of claim 1 , wherein no temporal motion predictor candidate is included in a motion predictor candidate list other than the temporal merge list.
6 . The method of claim 1 , wherein decoding the second flag in a merge mode uses the same second CABAC as decoding the second flag in an inter mode.
7 . The method of claim 1 , wherein the first flag and the second flag are decoded at a block level of the picture information.
8 . A non-transitory computer readable medium storing executable program instructions to cause a computer executing the instructions to perform a method according to claim 1 .
9 . The non-transitory computer readable medium of claim 8 , wherein:
the affine prediction mode indicates use of an affine motion compensation, and
the temporal merge list comprises a subblock temporal motion vector prediction mode which derives motion information for subblocks of a block from motion information in a reference picture of a picture to which the block belongs.
10 . A method comprising:
encoding a first flag associated with picture information, the first flag being encoded using a first Context-Based Arithmetic Coding (CABAC);
encoding a second flag associated with the picture information, the second flag being encoded using a second CABAC separate from the first CABAC; and
encoding at least a portion of the picture information based on a coding mode indicated by the first flag or the second flag to generate a bitstream, wherein:
the first flag indicates whether or not a temporal mode is used, wherein in the temporal mode a temporal merge list is constructed that comprises only temporal motion predictor candidates; and
the second flag indicates whether or not an affine prediction mode is used.
11 . The method of claim 10 , wherein:
the affine prediction mode indicates use of an affine motion compensation, and
the temporal merge list comprises a subblock temporal motion vector prediction mode which derives motion information for subblocks of a block from motion information in a reference picture of a picture to which the block belongs.
12 . The method of claim 10 , wherein the first flag and the second flag are encoded at a block level of the picture information.
13 . An apparatus comprising:
one or more processors configured to:
decode a first flag included in a bitstream, the first flag being associated with picture information, and the first flag having been coded using a first Context-Based Arithmetic Coding (CABAC);
decode a second flag included in the bitstream, the second flag being associated with the picture information, and the second flag having been coded using a second CABAC separate from the first CABAC; and
decode at least a portion of the picture information included in the bitstream based on a coding mode indicated by the first flag or the second flag, wherein:
the first flag indicates whether or not a temporal mode is used, wherein in the temporal mode a temporal merge list is constructed that comprises only temporal motion predictor candidates; and
the second flag indicates whether or not an affine prediction mode is used.
14 . The apparatus of claim 13 , wherein:
the affine prediction mode indicates use of an affine motion compensation, and
the temporal merge list comprises a subblock temporal motion vector prediction mode which derives motion information for subblocks of a block from motion information in a reference picture of a picture to which the block belongs.
15 . The apparatus of claim 13 , wherein decoding the second flag in a merge mode uses the same second CABAC as decoding the second flag in an inter mode.
16 . The apparatus of claim 13 , wherein the first flag and the second flag are decoded at a block level of the picture information.
17 . An apparatus comprising:
one or more processors configured to:
encode a first flag associated with picture information, the first flag being encoded using a first Context-Based Arithmetic Coding (CABAC);
encode a second flag associated with the picture information, the second flag being encoded using a second CABAC separate from the first CABAC; and
encode at least a portion of the picture information based on a coding mode indicated by the first flag or the second flag to generate a bitstream, wherein:
the first flag indicates whether or not a temporal mode is used, wherein in the temporal mode a temporal merge list is constructed that comprises only temporal motion predictor candidates; and
the second flag indicates whether or not an affine prediction mode is used.
18 . The apparatus of claim 17 , wherein:
the affine prediction mode indicates use of an affine motion compensation, and
the temporal merge list comprises a subblock temporal motion vector prediction mode which derives motion information for subblocks of a block from motion information in a reference picture of a picture to which the block belongs.
19 . The apparatus of claim 17 , wherein the first flag and the second flag are encoded at a block level of the picture information.