Method and apparatus of video coding with affine motion compensation

An apparatus of processing video data with affine motion compensation in a video coding system, the apparatus comprising one or more electronic circuits configured to:

• receive input data associated with a current block in a current picture;
• if the current block is coded or to be coded in affine Merge mode, derive a first affine Merge candidate for the current block including three affine motion vectors Mv0, Mv1, and Mv2 for predicting motion vectors at control points of the current block, wherein Mv0 is derived from a motion vector of a first neighboring coded block of the current block, Mv1 is derived from a motion vector of a second neighboring coded block of the current block, and Mv2 is derived from a motion vector of a third neighboring coded block of the current block;
• if the first affine Merge candidate is selected to encode or decode the current block, derive an affine motion model according to the affine motion vectors Mv0, Mv1, and Mv2 of the first affine candidate;
• and
• encode or decode the current block by locating a reference block in a reference picture for the current block according to the affine motion model.

A non-transitory computer readable medium storing program instruction causing a processing circuit of an apparatus to perform a video coding method with affine motion compensation, and the method comprising:

• receiving input data associated with a current block in a current picture;
• if the current block is coded or to be coded in affine Merge mode, deriving a first affine Merge candidate for the current block including three affine motion vectors Mv0, Mv1, and Mv2 for predicting motion vectors at control points of the current block, wherein Mv0 is derived from a motion vector of a first neighboring coded block of the current block, Mv1 is derived from a motion vector of a second neighboring coded block of the current block, and Mv2 is derived from a motion vector of a third neighboring coded block of the current block;
• if the first affine Merge candidate is selected to encode or decode the current block, deriving an affine motion model according to the affine motion vectors Mv0, Mv1, and Mv2 of the first affine Merge candidate;
• and
• encoding or decoding the current block by locating a reference block in a reference picture for the current block according to the affine motion model.