Method and apparatus of bi-directional optical flow displacement fusion for video coding

An apparatus for video coding, the apparatus comprising one or more electronics or processors arranged to:

• receive input data associated with a current block, wherein the input data comprise pixel data for the current block to be encoded at an encoder side or coded data associated with the current block to be decoded at a decoder side;
• determine a first motion offset for a first predictor based on a first reference picture and a second motion offset for a second predictor based on a second reference picture separately by using a BDOF (Bi-Directional Optical Flow) motion model without a constraint for the first motion offset and the second motion offset to have a same magnitude, wherein the first motion offset is derived for a list 0 reference block and the second motion offset is derived for a list 1 reference block, wherein the first motion offset and the second motion offset are derived to minimize differences between the first predictor and the second predictor;
• determine a bi-directional prediction offset value corresponding to the linear combination of the first motion offset for the list 0 reference block and the second motion offset for the list 1 reference block;
• and
• derive a bidirectional predictor for the current block based on the first predictor, the second predictor, and the bi-directional prediction offset value.