Affine motion vector predictor and affine merged motion vector by using lookahead/lookbehind motion vector

A method of video encoding, the method comprising:

• determining a first control point motion vector (CPMV) of a first control point of a current block in a current picture, the first CPMV being associated with a sum of a plurality of intermediate vectors that are defined based on a plurality of reference pictures of the current picture in a first temporal direction, the plurality of intermediate vectors including an initial CPMV and an intermediate motion vector (MV), the initial CPMV being between the current picture and an initial reference picture of the plurality of reference pictures in a reference list in the first temporal direction, and the intermediate MV being between two respective reference pictures of the plurality of reference pictures;
• encoding the current block based on the first CPMV of the first control point of the current block;
• and
• encoding a syntax element into a bitstream, the syntax element indicating that the current block is coded in an affine mode.

A non-transitory computer-readable storage medium storing instructions which, when executed by a processor, cause the processor to perform a method of encoding a bitstream comprising:

• determining a first control point motion vector (CPMV) of a first control point of a current block in a current picture, the first CPMV being associated with a sum of a plurality of intermediate vectors that are defined based on a plurality of reference pictures of the current picture in a first temporal direction, the plurality of intermediate vectors including an initial CPMV and an intermediate motion vector (MV), the initial CPMV being between the current picture and an initial reference picture of the plurality of reference pictures in a reference list in the first temporal direction, and the intermediate MV being between two respective reference pictures of the plurality of reference pictures;
• encoding the current block based on the first CPMV of the first control point of the current block;
• encoding a syntax element into the bitstream, the syntax element indicating that the current block is coded in an affine mode;
• and
• transmitting the encoded bitstream.