Video signal encoding and decoding method, and apparatus therefor

A video encoding method comprising the steps of:

• generating a merge candidate list for a current block;
• selecting a merge candidate for the current block among merge candidates included in the merge candidate list;
• deriving an offset vector for the current block;
• encoding first index information for specifying a motion magnitude candidate indicating a magnitude of the offset vector among a plurality of motion magnitude candidates,
• encoding second index information for specifying a vector direction candidate indicating a direction of the offset vector among a plurality of vector direction candidates,
• wherein the motion magnitude candidate has a value derived by applying an arithmetic left shift operation by two binary digits to the magnitude of the offset vector;
• and
• deriving a motion vector for the current block by adding the offset vector to a motion vector of the merge candidate;
• wherein the method further comprises the step of encoding a flag indicating a numerical range of the motion magnitude candidates, wherein at least one among a maximum numerical value and a minimum numerical value of the motion magnitude candidates is set differently according to a numerical value of the flag, and
• the flag is encoded at a picture level.

A video decoding device, comprising:

• a memory module storing instructions;
• a processing unit configured to, upon executing the instructions:
• generate a merge candidate list for a current block, determine a merge candidate for the current block among merge candidates included in the merge candidate list, derive an offset vector for the current block, wherein a magnitude of the offset vector is determined based on first index information specifying one among motion magnitude candidates, and a direction of the offset vector is determined based on second index information specifying one among vector direction candidates, wherein the magnitude of the offset vector is obtained by applying an arithmetic left shift operation by two binary digits to a value indicated by the motion magnitude candidate specified by the first index information, and derive a motion vector for the current block by adding the offset vector to a motion vector of the merge candidate;
• wherein at least one among a maximum numerical value and a minimum numerical value of the motion magnitude candidates is set differently according to a numerical value of a flag indicating a numerical range of the motion magnitude candidates, and
• the flag is signalled at a picture level.