A method for decoding a video according to the present invention may comprise: determining an intra prediction mode of a current block, deriving reference samples from neighboring samples of the current block, obtaining a first prediction sample for the current block, based on the intra prediction mode and the reference samples, determining an offset for the first prediction sample, and obtaining a second prediction sample by applying the offset to the first prediction sample.

A method for decoding a video according to the present invention may comprise: determining an intra prediction mode of a current block, deriving reference samples from neighboring samples of the current block, obtaining a first prediction sample for the current block, based on the intra prediction mode and the reference samples, determining an offset for the first prediction sample, and obtaining a second prediction sample by applying the offset to the first prediction sample.

An encoder includes memory and circuitry. The circuitry: derives a first motion vector in a unit of a prediction block using a first inter frame prediction mode that uses a degree of matching between two reconstructed images of two regions in two difference pictures, the prediction block being obtained by splitting an image included in a video; and performs, in the unit of the prediction block, a first motion compensation process that generates a prediction image by referring to a spatial gradient of luminance in an image generated by performing motion compensation using the first motion vector derived.

An encoder includes memory and circuitry. The circuitry: derives a first motion vector in a unit of a prediction block using a first inter frame prediction mode that uses a degree of matching between two reconstructed images of two regions in two difference pictures, the prediction block being obtained by splitting an image included in a video; and performs, in the unit of the prediction block, a first motion compensation process that generates a prediction image by referring to a spatial gradient of luminance in an image generated by performing motion compensation using the first motion vector derived.

An image decoding method according to the present document may comprise the steps of: deriving an inter prediction mode from encoded information; configuring reference picture lists, deriving motion information comprising reference picture indexes for symmetric motion vector differences (SMVD); and generating prediction samples on the basis of the motion information, wherein the reference picture indexes for SMVD can be derived on the basis of short-term reference pictures included within the reference picture lists.

An image decoding method according to the present document may comprise the steps of: deriving an inter prediction mode from encoded information; configuring reference picture lists, deriving motion information comprising reference picture indexes for symmetric motion vector differences (SMVD); and generating prediction samples on the basis of the motion information, wherein the reference picture indexes for SMVD can be derived on the basis of short-term reference pictures included within the reference picture lists.

A video decoder may be configured to generate a first ordering of reference pictures in a reference picture list for a first block of a slice, wherein generating the first ordering of the reference pictures for the first block comprises assigning indexes to the reference pictures; and generate a second ordering of the reference pictures in the reference picture list for a second block of the slice based on an adaptive reference picture reordering process, wherein the first ordering is different than the second ordering and generating the second ordering of reference pictures for the second block comprises assigning at least some of the indexes to different reference pictures than in the first ordering; decode the first block using the first ordering of the reference pictures; and decode the second block using the second ordering of the reference pictures.

An image decoding method is disclosed in the present specification. An image decoding method according to the present invention may comprise determining a prediction mode of a current block and performing prediction with respect to the current block on the basis of the determined prediction mode.

An image decoding method is disclosed in the present specification. An image decoding method according to the present invention may comprise determining a prediction mode of a current block and performing prediction with respect to the current block on the basis of the determined prediction mode.

Interpolation between explicitly signaled CPB (or HRD) parameters at selected bit rates is used to achieve a good compromise between CPB parameter transmission capacity and CPB parametrization effectiveness and may be, particularly, made in an effective manner.