Multiple merge candidates for affine motion prediction

A method for video decoding, comprising:

• accessing, for a block being decoded in a picture, an index corresponding to a predictor candidate, wherein the predictor candidate corresponds to a spatial or a temporal neighboring block that has been decoded, and wherein said block is decoded in an affine merge mode;
• obtaining, using a plurality of motion vectors associated with the predictor candidate, a set of control point motion vectors for the block being decoded;
• obtaining, based on the set of control point motion vectors, a motion field based on a motion model, wherein the motion field identifies motion vectors used for prediction of all sub-blocks of the block being decoded;
• and
• decoding the block based on the motion field.

An apparatus for video encoding, comprising:

• one or more processors, wherein said one or more processors are configured to:
• access, for a block being encoded in a picture, a set of predictor candidates having multiple predictor candidates, wherein a predictor candidate corresponds to a spatial or a temporal neighboring block that has been encoded, wherein said block is encoded in an affine merge mode;
• select a predictor candidate from the set of predictor candidates;
• obtain, using a plurality of motion vectors associated with the selected predictor candidate from the set of predictor candidates, a set of control point motion vectors for the block;
• obtain, based on the set of control point motion vectors, a motion field based on a motion model, wherein the motion field identifies motion vectors used for prediction of all sub-blocks of the block being encoded;
• encode the block based on the motion field;
• and
• encode an index for the selected predictor candidate from the set of predictor candidates.

An apparatus for video decoding, comprising:

• one or more processors, wherein the one or more processors are configured to:
• access, for a block being decoded in a picture, an index corresponding to a predictor candidate, wherein the predictor candidate corresponds to a spatial or a temporal neighboring block that has been decoded, and wherein said block is decoded in an affine merge mode;
• obtain, using a plurality of motion vectors associated with the predictor candidate, a set of control point motion vectors for the block being decoded;
• obtain, based on the set of control point motion vectors, a motion field based on a motion model, wherein the motion field identifies motion vectors used for prediction of all sub-blocks of the block being decoded;
• and
• decode the block based on the motion field.