A method for processing a video includes performing a conversion between a current block of visual media data and a corresponding coded representation of the visual media data, wherein the conversion of the current block includes determining whether a use of one or both of a bi-directional optical flow (BIO) technique or a decoder-side motion vector refinement (DMVR) technique to the current block is enabled or disabled, and wherein the determining the use of the BIO technique or the DMVR technique is based on a cost criterion associated with the current block.

Disclosed is a video signal processing method comprising the steps of: acquiring a merge index which indicates a candidate for prediction of a current block among a plurality of candidates for the prediction of the current block, which are included in a merge candidate list; acquiring motion information of the current block on the basis of motion information corresponding to the candidate indicated by the merge index; when the motion information of the current block includes a plurality of motion vectors corresponding to a list of different reference pictures, comparing picture order count (POC) differences between each of the reference pictures corresponding to the plurality of motion vectors and the current picture including the current block; correcting the plurality of motion vectors on the basis of a result of the comparison; and reconstructing the current block on the basis of the plurality of corrected motion vectors.

A motion vector coding unit executes processing including a neighboring block specification step of specifying a neighboring block which is located in the neighborhood of a current block; a judgment step of judging whether or not the neighboring block has been coded using a motion vector of another block; a prediction step of deriving a predictive motion vector of the current block using a motion vector calculated from the motion vector of the other block as a motion vector of the neighboring block; and a coding step of coding the motion vector of the current block using the predictive motion vector.

A motion vector coding unit executes processing including a neighboring block specification step of specifying a neighboring block which is located in the neighborhood of a current block; a judgment step of judging whether or not the neighboring block has been coded using a motion vector of another block; a prediction step of deriving a predictive motion vector of the current block using a motion vector calculated from the motion vector of the other block as a motion vector of the neighboring block; and a coding step of coding the motion vector of the current block using the predictive motion vector.

According to the present invention, an image encoding apparatus comprises: a motion prediction unit which derives motion information on a current block in the form of the motion information including L0 motion information and L1 motion information; a motion compensation unit which performs a motion compensation for the current block on the basis of at least one of the L0 motion information and L1 motion information so as to generate a prediction block corresponding to the current block; and a restoration block generating unit which generates a restoration block corresponding to the current block based on the prediction block. According to the present invention, image encoding efficiency can be improved.

According to the present invention, an image encoding apparatus comprises: a motion prediction unit which derives motion information on a current block in the form of the motion information including L0 motion information and L1 motion information; a motion compensation unit which performs a motion compensation for the current block on the basis of at least one of the L0 motion information and L1 motion information so as to generate a prediction block corresponding to the current block; and a restoration block generating unit which generates a restoration block corresponding to the current block based on the prediction block. According to the present invention, image encoding efficiency can be improved.

An example method of video processing includes performing a conversion between a video picture of a video and a bitstream representation of the video. The bitstream representation conforms to a format rule. The format rule specifies that applicability of a Decoder-side Motion Vector Refinement coding tool and a Bi-Directional Optical Flow coding tool for the video picture are indicated separately in the bitstream representation.

Particular embodiments provide a variable, BitDepth, that may be set at a value based on a number of bits used to represent pixels in pictures of a video. The variable may be used in syntax elements in HEVC, such as the HEVC range extension, but other coding standards may be used. By using the variable, different resolutions for the video may be accommodated during the encoding and decoding process. For example, the number of pixels in the pictures may be represented by 8 bits, 10 bits, 12 bits, or another number of bits depending on the resolution. Using the BitDepth variable in the syntax provides flexibility in the motion estimation and motion compensation process. For example, syntax elements used in the weighted prediction process may take into account different numbers of bits used to represent the pictures.

An image decoding method performed by a decoding device according to the present disclosure comprises: a step of deriving reference picture list 0 (L0) and reference picture list 1 (L1); a step of deriving two motion vectors (MV) for a current block, the two MVs including MVL0 for the L0 and MVL1 for the L1; a step of determining whether to apply bi-prediction optical flow (BIO) prediction for deriving refined motion vectors by sub-blocks to the current block; a step of deriving a refined motion vector for a sub-block of the current block based on the MVL0 and MVL1, if the BIO prediction is applied to the current block; and a step of deriving a prediction sample based on the refined motion vector.

An image decoding method performed by a decoding device according to the present disclosure comprises: a step of deriving reference picture list 0 (L0) and reference picture list 1 (L1); a step of deriving two motion vectors (MV) for a current block, the two MVs including MVL0 for the L0 and MVL1 for the L1; a step of determining whether to apply bi-prediction optical flow (BIO) prediction for deriving refined motion vectors by sub-blocks to the current block; a step of deriving a refined motion vector for a sub-block of the current block based on the MVL0 and MVL1, if the BIO prediction is applied to the current block; and a step of deriving a prediction sample based on the refined motion vector.