| CPC H04N 19/105 (2014.11) [H04N 19/159 (2014.11); H04N 19/176 (2014.11); H04N 19/52 (2014.11)] | 8 Claims |
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1. A video decoding method for decoding a sequence of pictures, the method comprising:
decoding, at a sequence level of a bitstream, enabling information indicating whether a first coding tool of a plurality of coding tools is allowed for the sequence;
decoding, at a picture level associated with a current picture to be decoded, group identification information when the enabling information indicates that the first coding tool is allowed for the sequence, and thereby selecting a candidate set to be used for blocks in the current picture from a plurality of candidate sets;
decoding, at a block level associated with a current block in the current picture, an mmvd flag indicating whether the first coding tool has been applied to the current block, depending on the enabling information; and
when the mmvd flag indicates that the first coding tool has been applied to the current block,
decoding, at the block level, a merge candidate identification information and offset information;
selecting a merge candidate corresponding to the merge candidate identification information from a merge candidate list which includes merge candidates derived from neighboring blocks of the current block;
deriving, using the offset information, an offset vector for the current block from a plurality of offset vectors defined by the candidate set which is selected at the picture level by the group identification information;
deciding at least one motion vector of the current block by applying the offset vector to at least one motion vector of the selected merge candidate; and
predicting the current block using the at least one motion vector of the current block,
wherein, when the selected merge candidate is a pre-decoded block that has been bi-predicted using two motion vector, the deciding the at least one motion vector of the current block comprises:
adding the offset vector indicated by the offset information to a motion vector for a specific prediction direction of the selected merge candidate to decide a motion vector for the specific prediction direction of the current block;
scaling the offset vector indicated by the offset information, based on a ratio of a time-axis distance between a current picture and a reference picture for the specific prediction direction referenced by the selected merge candidate and a time-axis distance between the current picture and a reference picture for the other prediction direction referenced by the selected merge candidate; and
adding the scaled offset vector to a motion vector for the other prediction direction of the selected merge candidate to decide a motion vector for the other prediction direction of the current block.
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