Affine merge mode with translational motion vectors

A method of video processing in a decoder, comprising:

• receiving a coded video bitstream comprising a current block in a current picture;
• determining, from a candidate list, a first affine-translational merge candidate for a prediction of the current block in the current picture when a high level syntax in the coded video bitstream is determined to indicate that the first affine-translational merge candidate for the prediction of the current block is allowed, the first affine-translational merge candidate providing affine motion information associated with a first reference picture in a first reference list and translational motion information associated with a second reference picture in a second reference list, the first affine-translational merge candidate providing different types of motion information associated with different reference pictures, the first reference picture being different from the second reference picture, the translational motion information associated with the second reference picture being non-symmetric to the affine motion information associated with the first reference picture;
• generating a first prediction for a sample in the current block according to the affine motion information associated with the first reference picture;
• generating a second prediction for the sample in the current block according to the translational motion information associated with the second reference picture;
• and
• reconstructing the sample of the current block according to a combination of the first prediction and the second prediction.