In a method for video encoding in an encoder, a base predictor of a block in a current picture is determined. A plurality of offset indexes in a plurality of respective pre-defined mapping tables is determined, the plurality of offset indexes indicating corresponding offset values to be applied to parameters of an affine model for the base predictor. A coded video bitstream is generated, the coded video bitstream including prediction information that indicates the plurality of offset indexes. The pre-defined mapping tables include a first mapping table of distance offset indexes that are mapped to different pixel distances and a second mapping table of offset direction indexes that are mapped to different pairs of offset directions on an x-axis and a y-axis.