Image coding method based on motion vector and apparatus therefor

A picture encoding method performed by an encoding apparatus comprising:

• deriving a motion vector for a current block in a current picture;
• deriving a predicted block for the current block based on the motion vector for the current block;
• deriving information related to motion vector compression;
• deriving a scaled motion vector based on the information related to the motion vector compression;
• storing information about the motion vector for the current block, wherein the information about the motion vector comprises information about the scaled motion vector for the motion vector;
• deriving residual samples for the current block based on the predicted block for the current block;
• and
• encoding image information comprising information about the residual samples,
• wherein the predicted block for the current block is derived based on inter prediction,
• wherein the information related to the motion vector compression includes information related to a number of bits for representing the scaled motion vector, information about a scale factor for the motion vector, and information about a sign and motion data for the motion vector,
• wherein the number of bits for representing the scaled motion vector is less than 16, and
• wherein the information about the sign and the motion data is represented by 6 bits.

A non-transitory computer-readable digital storage medium storing bitstream generated by a method, the method comprising:

• performing deriving a motion vector for a current block in a current picture, deriving a predicted block for the current block based on the motion vector for the current block, deriving information related to motion vector compression, deriving a scaled motion vector based on the information related to the motion vector compression, storing information about the motion vector for the current block, wherein the information about the motion vector comprises information about the scaled motion vector for the motion vector, deriving residual samples for the current block based on the predicted block for the current block and generating the bitstream by encoding image information comprising information about the residual samples,
• wherein the predicted block for the current block is derived based on inter prediction,
• wherein the information related to the motion vector compression includes information related to a number of bits for representing the scaled motion vector, information about a scale factor for the motion vector, and information about a sign and motion data for the motion vector,
• wherein the number of bits for representing the scaled motion vector is less than 16, and
• wherein the information about the sign and the motion data is represented by 6 bits.

A transmission method of data for an image, the transmission method comprising:

• obtaining bitstream generated by performing deriving a motion vector for a current block in a current picture, deriving a predicted block for the current block based on the motion vector for the current block, deriving information related to motion vector compression, deriving a scaled motion vector based on the information related to the motion vector compression, storing information about the motion vector for the current block, wherein the information about the motion vector comprises information about the scaled motion vector for the motion vector, deriving residual samples for the current block based on the predicted block for the current block and generating the bitstream by encoding image information comprising information about the residual samples, and
• transmitting the data comprising the bitstream,
• wherein the predicted block for the current block is derived based on inter prediction,
• wherein the information related to the motion vector compression includes information related to a number of bits for representing the scaled motion vector, information about a scale factor for the motion vector, and information about a sign and motion data for the motion vector,
• wherein the number of bits for representing the scaled motion vector is less than 16, and
• wherein the information about the sign and the motion data is represented by 6 bits.