Picture decoding device, picture decoding method, and picture decoding program with history-based candidate selection
A picture decoding device includes a spatial candidate derivation unit configured to derive a spatial candidate from inter prediction information of a block neighboring a decoding target block and register the derived spatial candidate as a candidate to a first candidate list, a history-based candidate derivation unit configured to generate a second candidate list by adding a history-based candidate included in a history-based candidate list as a candidate to the first candidate list, a candidate selection unit configured to select a selection candidate from candidates included in the second candidate list, and an inter prediction unit configured to perform inter prediction using the selection candidate.
1. A picture coding device for coding a moving picture using inter prediction in units of blocks and forming a bitstream, the picture coding device comprising:
a spatial motion vector predictor candidate derivation unit configured to derive a spatial candidate from inter prediction information of a block neighboring a coding target block and register the derived spatial candidate to a first motion vector predictor candidate list;
a history-based motion vector predictor candidate derivation unit configured to generate a second motion vector predictor candidate list by adding a history-based candidate to the first motion vector predictor candidate list regardless of whether or not a motion vector of the history-based candidate included in a history-based candidate list overlaps motion vectors of candidates included in the first motion vector candidate list;
a motion vector predictor candidate selection unit configured to select a first selection candidate from candidates included in the second motion vector predictor candidate list;
a spatial merge candidate derivation unit configured to derive a spatial candidate from inter prediction information of a block neighboring a coding target block and register the derived spatial candidate to a first merge candidate list;
a history-based merge candidate derivation unit configured to generate a second merge candidate list by adding a history-based candidate to the first merge candidate list when the history-based candidate included in the history-based candidates list does not overlap candidates included in the first merge candidate list; and
a merge candidate selection unit configured to select a second selection candidate from candidates included in the second merge candidate list;
a coding unit configured to code a merge flag being 1 in a merge mode and being 0 in a motion vector predictor mode, and code a merge index for selecting the second selection candidates when the merge flag is 1 and code a motion vector predictor index for selecting the first selection candidate when the merge flag is 0; and
an inter prediction unit configured to perform inter prediction using the first selection candidate or the second selection candidate.
2. A picture coding method for coding a moving picture using inter prediction in units of blocks and forming a bitstream, the picture coding method comprising:
deriving a spatial candidate from inter prediction information of a block neighboring a coding target block and register the derived spatial candidate to a first motion vector predictor candidate list;
generating a second motion vector predictor candidate list by adding a history-based candidate to the first motion vector predictor candidate list regardless of whether or not a motion vector of the history-based candidate included in a history-based candidate list overlaps motion vectors of candidates included in the first motion vector candidate list;
selecting a first selection candidate from candidates included in the second motion vector predictor candidate list;
deriving a spatial candidate from inter prediction information of a block neighboring a coding target block and register the derived spatial candidate to a first merge candidate list;
generating a second merge candidate list by adding a history-based candidate to the first merge candidate list when the history-based candidate included in the history-based candidates list does not overlap candidates included in the first merge candidate list; and
selecting a second selection candidate from candidates included in the second merge candidate list;
coding a merge flag being 1 in a merge mode and being 0 in a motion vector predictor mode, and coding a merge index for selecting the second selection candidates when the merge flag is 1 and coding a motion vector predictor index for selecting the first selection candidate when the merge flag is 0; and
performing inter prediction using the first selection candidate or the second selection candidate.
3. A picture decoding device comprising:
a spatial motion vector predictor candidate derivation unit configured to derive a spatial candidate from inter prediction information of a block neighboring a decoding target block and register the derived spatial candidate to a first motion vector predictor candidate list;
a history-based motion vector predictor candidate derivation unit configured to generate a second motion vector predictor candidate list by adding a history-based candidate to the first motion vector predictor candidate list regardless of whether or not a motion vector of the history-based candidate included in a history-based candidate list overlaps motion vectors of candidates included in the first motion vector candidate list;
a motion vector predictor candidate selection unit configured to select a first selection candidate from candidates included in the second motion vector predictor candidate list;
a spatial merge candidate derivation unit configured to derive a spatial candidate from inter prediction information of a block neighboring a decoding target block and register the derived spatial candidate to a first merge candidate list;
a history-based merge candidate derivation unit configured to generate a second merge candidate list by adding a history-based candidate to the first merge candidate list when the history-based candidate included in the history-based candidates list does not overlap candidates included in the first merge candidate list; and
a merge candidate selection unit configured to select a second selection candidate from candidates included in the second merge candidate list;
a decoding unit configured to decode a merge flag being 1 in a merge mode and being 0 in a motion vector predictor mode, and decode a merge index for selecting the second selection candidates when the merge flag is 1 and decode a motion vector predictor index for selecting the first selection candidate when the merge flag is 0; and
an inter prediction unit configured to perform inter prediction using the first selection candidate or the second selection candidate.
4. A picture decoding method comprising:
deriving a spatial candidate from inter prediction information of a block neighboring a decoding target block and registering the derived spatial candidate to a first motion vector predictor candidate list;
generating a second motion vector predictor candidate list by adding a history-based candidate to the first motion vector predictor candidate list regardless of whether or not a motion vector of the history-based candidate included in a history-based candidate list overlaps motion vectors of candidates included in the first motion vector candidate list;
selecting a first selection candidate from candidates included in the second motion vector predictor candidate list;
deriving a spatial candidate from inter prediction information of a block neighboring a decoding target block and registering the derived spatial candidate to a first merge candidate list;
generating a second merge candidate list by adding a history-based candidate to the first merge candidate list when the history-based candidate included in the history-based candidates list does not overlap candidates included in the first merge candidate list; and
selecting a second selection candidate from candidates included in the second merge candidate list;
decoding a merge flag being 1 in a merge mode and being 0 in a motion vector predictor mode, and decoding a merge index for selecting the second selection candidates when the merge flag is 1 and decoding a motion vector predictor index for selecting the first selection candidate when the merge flag is 0; and
performing inter prediction using the first selection candidate or the second selection candidate.
5. A storing method for storing a bitstream formed by the picture coding method according to claim 2 in a recording medium.
6. A transmitting method for transmitting a bitstream formed by the picture coding method according to claim 2 .
7. A non-transitory computer readable medium storing a bitstream formed by the picture coding method according to claim 2 .