Sub-block division-based image encoding/decoding method and device

A video encoding method, the method comprising:

• determining a block partitioning structure of a current block;
• deriving first motion information for a first sub-block of the current block and second motion information for a second sub-block of the current block respectively;
• encoding block partitioning information based on the block partitioning structure;
• and
• encoding a first merge index for the first sub-block and a second merge index for the second sub-block respectively based on the first motion information and the second motion information;
• and
• storing at least one of the first motion information for the first sub-block, the second motion information for the second sub-block, and third motion information based on a value of sType,
• wherein the block partitioning information is index information indicating an index of a table including information indicating a plurality of predefined asymmetric partition shapes for the first sub-block and the second sub-block,
• wherein, in response to the value of sType being 2 and the first motion information and the second motion information referring to a reference picture in a same direction, L1 motion information of the third motion information is set identical to the second motion information for the second sub-block, and L0 motion vector of L0 motion information of the third motion information is set to 0 for horizontal and vertical directions, and L0 reference picture index of the L0 motion information is set to a value of −1, and
• wherein the current block is obtained by dividing a current picture including the current block using a quad-tree division method.

A method of transmitting a bitstream generated by a video encoding method, the video encoding method comprising:

• determining a block partitioning structure of a current block;
• deriving first motion information for a first sub-block of the current block and second motion information for a second sub-block of the current block respectively;
• encoding block partitioning information based on the block partitioning structure;
• encoding a first merge index for the first sub-block and a second merge index for the second sub-block respectively based on the first motion information and the second motion information;
• and
• storing at least one of the first motion information for the first sub-block, the second motion information for the second sub-block, and third motion information based on a value of sType,
• wherein the block partitioning information is index information indicating an index of a table including information indicating a plurality of predefined asymmetric partition shapes for the first sub-block and the second sub-block,
• wherein, in response to the value of sType being 2 and the first motion information and the second motion information referring to a reference picture in a same direction, L1 motion information of the third motion information is set identical to the second motion information for the second sub-block, and L0 motion vector of L0 motion information of the third motion information is set to 0 for horizontal and vertical directions, and L0 reference picture index of the L0 motion information is set to a value of −1, and
• wherein the current block is obtained by dividing a current picture including the current block using a quad-tree division method.