Method and apparatus for encoding/decoding images using adaptive motion vector resolution

A video encoding apparatus for encoding a motion vector by using an adaptive motion vector resolution in the unit of blocks which are split from a picture to be encoded, the apparatus comprising:

• an inter predictor configured to determine a current motion vector of a current block to be encoded among the blocks split from the picture;
• and
• an encoder configured to
• encode, into a bitstream, mode information for use in determining one of a plurality of motion vector encoding modes;
• when the mode information represents a first mode that a differential motion vector is encoded into the bitstream, encode, into the bitstream, a differential motion vector and motion vector resolution identification information which are dedicated to the current block, wherein the motion vector resolution identification information is used for determining a motion vector resolution of the differential motion vector among a plurality of motion vector resolutions,
• wherein the encoder is configured to
• derive at least one predicted motion vector candidate from motion vectors of one or more neighboring blocks of the current block,
• convert the predicted motion vector candidate such that the converted predicted motion vector candidate has the same motion vector resolution as the motion vector resolution determined by the motion vector resolution identification information,
• derive a predicted motion vector for the current motion vector from the converted predicted motion vector candidate, and
• generate the differential motion vector by subtracting the predicted motion vector from the current motion vector.

A non-transitory recording medium storing a bitstream generated by a video encoding method for encoding blocks, which are split from a picture to be encoded, by using an adaptive motion vector resolution in the unit of blocks, the method comprising:

• determining a current motion vector of a current block to be encoded among the blocks split from the picture;
• and
• encoding, into a bitstream, mode information for use in determining one of a plurality of motion vector encoding modes;
• when the mode information represents a first mode that a differential motion vector is encoded in the bitstream, encoding, into the bitstream, a differential motion vector and motion vector resolution identification information which are dedicated to the current block, wherein the motion vector resolution identification information is used for determining a motion vector resolution of the differential motion vector among a plurality of motion vector resolutions,
• wherein the encoding of the differential motion vector comprises:
• deriving at least one predicted motion vector candidate from motion vectors of one or more neighboring blocks of the current block,
• converting the predicted motion vector candidate such that the converted predicted motion vector candidate has the same motion vector resolution as the motion vector resolution determined by the motion vector resolution identification information,
• deriving a predicted motion vector for the current motion vector from the converted predicted motion vector candidate, and
• generating the differential motion vector by subtracting the predicted motion vector from the current motion vector.