Video decoding method and apparatus and video encoding method and apparatus

A video decoding method comprising:

• obtaining, from a bitstream, a motion vector difference resolution index;
• obtaining motion vector difference resolution set information;
• determining a motion vector difference resolution of a current block, based on the motion vector difference resolution index and the motion vector difference resolution set information;
• obtaining, from the bitstream, motion vector difference of the current block;
• adjusting the motion vector difference based on the motion vector difference resolution;
• and
• obtaining a motion vector of the current block by using a prediction motion vector and the adjusted motion vector difference,
• wherein the motion vector difference resolution set information indicates one motion vector difference resolution set among a plurality of motion vector difference resolution sets, the one motion vector difference resolution set including a plurality of motion vector difference resolutions,
• wherein the plurality of motion vector difference resolutions are predetermined and the motion vector difference resolution index corresponds to one motion vector difference resolution among the plurality of motion vector difference resolutions included in the motion vector difference resolution set which is indicated by the motion vector difference resolution set information,
• wherein the prediction motion vector is obtained by using a motion vector of a neighboring block of the current block.