Method and device for inducing motion information between temporal points of sub prediction unit

A method of encoding an image, the method comprising:

• determining motion information of a current block;
• and
• encoding the motion information of the current block,
• wherein the deriving motion information of the current block comprises:
• determining whether a center sub block within a reference block has motion information;
• when the center sub block within the reference block has motion information, deriving motion information of sub blocks within the current block from sub blocks within the reference block;
• and
• when the center sub block within the reference block does not have motion information, terminating the deriving motion information of sub blocks within the current block from sub blocks within the reference block,
• wherein the center sub block corresponds to a center position of the current block, and
• wherein the motion information includes a motion vector.

A non-transitory computer readable recording medium storing a bitstream formed by a method of encoding an image, the method comprising:

• deriving motion information of a current block;
• and
• deriving a prediction sample for the current block based on the motion information of the current block,
• wherein the deriving motion information of the current block comprises:
• determining whether a center sub block within a reference block has motion information;
• when the center sub block within the reference block has motion information, deriving motion information of sub blocks within the current block from sub blocks within the reference block;
• and
• when the center sub block within the reference block does not have motion information, terminating the deriving motion information of sub blocks within the current block from sub blocks within the reference block,
• wherein the center sub block corresponds to a center position of the current block, and
• wherein the motion information includes a motion vector.