An image decoding method includes obtaining, from a bitstream, first information indicating a motion vector resolution of a current unit among plural motion vector resolutions including a first motion vector resolution and a second motion vector resolution, and obtaining, from the bitstream, second information indicating whether a merge mode is applied to the current unit or not when the first information indicates the first motion vector resolution. The current unit is decoded based on the merge mode when the second information indicates that the merge mode is applied to the current unit. When the first information indicates the second motion vector resolution, the second information is not obtained from the bitstream. A picture is split into one or more largest coding units, and a largest coding unit among the one or more largest coding units is split into one or more coding units including the current unit.

Devices, systems and methods for digital video coding, which includes an overlapped block motion compensation (OBMC) process based on spatially neighboring blocks, are described. An exemplary method for video processing includes generating a motion information associated with a current video block; generating, based on a weighted sum of at least two temporary prediction blocks, a prediction block for the current video block, a first of the at least two temporary prediction blocks being based on the motion information, and a second of the at least two temporary prediction blocks being based on an intra prediction mode of a neighboring block; and performing, based on the prediction block, a conversion between the current video block and a bitstream representation of the current video block.

Devices, systems and methods for digital video coding, which includes an overlapped block motion compensation (OBMC) process based on spatially neighboring blocks, are described. An exemplary method for video processing includes generating a motion information associated with a current video block; generating, based on a weighted sum of at least two temporary prediction blocks, a prediction block for the current video block, a first of the at least two temporary prediction blocks being based on the motion information, and a second of the at least two temporary prediction blocks being based on an intra prediction mode of a neighboring block; and performing, based on the prediction block, a conversion between the current video block and a bitstream representation of the current video block.

In a method for video encoding in an encoder, a base predictor of a block in a current picture is determined. A plurality of offset indexes in a plurality of respective pre-defined mapping tables is determined, the plurality of offset indexes indicating corresponding offset values to be applied to parameters of an affine model for the base predictor. A coded video bitstream is generated, the coded video bitstream including prediction information that indicates the plurality of offset indexes. The pre-defined mapping tables include a first mapping table of distance offset indexes that are mapped to different pixel distances and a second mapping table of offset direction indexes that are mapped to different pairs of offset directions on an x-axis and a y-axis.

In a method for video encoding in an encoder, a base predictor of a block in a current picture is determined. A plurality of offset indexes in a plurality of respective pre-defined mapping tables is determined, the plurality of offset indexes indicating corresponding offset values to be applied to parameters of an affine model for the base predictor. A coded video bitstream is generated, the coded video bitstream including prediction information that indicates the plurality of offset indexes. The pre-defined mapping tables include a first mapping table of distance offset indexes that are mapped to different pixel distances and a second mapping table of offset direction indexes that are mapped to different pairs of offset directions on an x-axis and a y-axis.

The disclosure relates to table maintenance for HMVP candidate storage. A method for processing video, including: determining, during a conversion between a first block of visual media data and a corresponding coded representation of the visual media data, the first block being coded with geometry partition mode; determining, based on at least one table storing history based motion vector prediction (HMVP) candidates which include motion information based on previously coded blocks, motion information of at least one sub-portion of the first block; performing the conversion of the first block using the determined motion information.

The disclosure relates to table maintenance for HMVP candidate storage. A method for processing video, including: determining, during a conversion between a first block of visual media data and a corresponding coded representation of the visual media data, the first block being coded with geometry partition mode; determining, based on at least one table storing history based motion vector prediction (HMVP) candidates which include motion information based on previously coded blocks, motion information of at least one sub-portion of the first block; performing the conversion of the first block using the determined motion information.

The present invention discloses a method and apparatus for encoding or decoding a video signal. The method for processing a video signal according to the present invention uses a merging mode in which prediction information on a neighbor unit is used instead of transmitting prediction information on the present unit, so as to improve coding efficiency. In this case, the number of available candidate units for merging among the units in a predetermined position is determined, and information for the merging mode is acquired on the basis of the number of the available candidate units for merging. The unit to be merged is determined using the information for the merging mode, and prediction information on the unit to be merged is acquired. The prediction value for the present unit is acquired using the prediction information on the unit to be merged, and the present unit is restored using the acquired prediction value.

The present invention discloses a method and apparatus for encoding or decoding a video signal. The method for processing a video signal according to the present invention uses a merging mode in which prediction information on a neighbor unit is used instead of transmitting prediction information on the present unit, so as to improve coding efficiency. In this case, the number of available candidate units for merging among the units in a predetermined position is determined, and information for the merging mode is acquired on the basis of the number of the available candidate units for merging. The unit to be merged is determined using the information for the merging mode, and prediction information on the unit to be merged is acquired. The prediction value for the present unit is acquired using the prediction information on the unit to be merged, and the present unit is restored using the acquired prediction value.

Various embodiments for calculating a motion vector predictor for decoding a motion vector of a current block are provided. The motion vector is selected from a candidate list. When a motion vector used for coding a first block spatially adjacent to the current block in a current picture is useable for coding the current block, one or more first candidates is added to the candidate list based on the motion vector used for coding the first block. A second candidate is added to the candidate list based on a motion vector used for coding a second block within a first collocated picture. When a total number of available candidates in the candidate list is less than a predetermined number, a third candidate is added to the candidate list based on a motion vector used for coding a third block within a second collocated picture.