Image signal encoding/decoding method and non-transitory computer-readable medium

A video encoding method, comprising:

• in response to that a top boundary of a current block is in contact with a top boundary of a coding tree unit of the current block, obtaining a first affine seed vector of a bottom-left corner control point of a top affine neighboring block of a current block and a second affine seed vector of a bottom-right corner control point of the top affine neighboring block;
• deriving a third affine seed vector and a fourth affine seed vector of the current block based on the first affine seed vector and the second affine seed vector of the top affine neighboring block;
• deriving an affine vector for a subblock in the current block by using the third affine seed vector and the fourth affine seed vector of the current block, wherein the subblock is a region of a size smaller than that of the current block;
• and
• performing a motion compensation prediction for the subblock based on the affine vector.

A video decoder configured to perform following operations:

• in response to that a top boundary of a current block is in contact with a top boundary of a coding tree unit of the current block, obtaining a first affine seed vector of a bottom-left corner control point of a top affine neighboring block of a current block and a second affine seed vector of a bottom-right corner control point of the top affine neighboring block;
• deriving a third affine seed vector and a fourth affine seed vector of the current block based on the first affine seed vector and the second affine seed vector of the top affine neighboring block;
• deriving an affine vector for a subblock in the current block by using the third affine seed vector and the fourth affine seed vector of the current block, wherein the subblock is a region of a size smaller than that of the current block;
• and
• performing a motion compensation prediction for the subblock based on the affine vector.