Affine motion vector prediction in video coding

An apparatus configured to decode video data, the apparatus comprising:

• a memory configured to store a current block of video data;
• and
• one or more processors in communication with the memory, wherein the apparatus is configured to:
• receive the current block of video data that is to be decoded using affine motion compensation;
• construct an affine motion vector predictor (MVP) list for a plurality of control points of an affine model used to code the current block of video data, including adding a motion vector from a neighboring block of video data to the affine MVP list as a motion vector predictor based on the motion vector having an associated reference picture that is the same as a target reference picture for the current block of video data, and refraining from adding the motion vector from the neighboring block of video data to the affine MVP list as a motion vector predictor based on the motion vector not having the associated reference picture that is the same as the target reference picture for the current block of video data,
• wherein to construct the affine MVP list, the apparatus is further configured to derive a single candidate from a plurality of motion vector predictors, wherein the plurality of motion vector predictors includes a first motion vector predictor (MVP0), a second motion vector predictor (MVP1), and a third motion vector predictor (MVP2) based on the affine model being a 6-parameter affine model, and wherein the plurality of motion vector predictors includes the first motion vector predictor (MVP0) and the second motion vector predictor (MVP1) based on the affine model being a 4-parameter affine model;
• determine motion vectors for the plurality of control points using the affine MVP list;
• and
• decode the current block of video data with the determined motion vectors for the plurality of control points of the current block of video data.

An apparatus configured to decode video data, the apparatus comprising:

• means for receiving a current block of video data that is to be decoded using affine motion compensation;
• means for constructing an affine motion vector predictor (MVP) list for a plurality of control points of an affine model used to code the current block of video data, including adding a motion vector from a neighboring block of video data to the affine MVP list as a motion vector predictor based on the motion vector having an associated reference picture that is the same as a target reference picture for the current block of video data, and refraining from adding the motion vector from the neighboring block of video data to the affine MVP list as a motion vector predictor based on the motion vector not having the associated reference picture that is the same as the target reference picture for the current block of video data,
• wherein the means for constructing the affine MVP list further comprises means for deriving a single candidate from a plurality of motion vector predictors, wherein the plurality of motion vector predictors includes a first motion vector predictor (MVP0), a second motion vector predictor (MVP1), and a third motion vector predictor (MVP2) based on the affine model being a 6-parameter affine model, and wherein the plurality of motion vector predictors includes the first motion vector predictor (MVP0) and the second motion vector predictor (MVP1) based on the affine model being a 4-parameter affine model;
• means for determining motion vectors for the plurality of control points using the affine MVP list;
• and
• means for decoding the current block of video data with the determined motion vectors for the plurality of control points of the current block of video data.

An apparatus configured to encode video data, the apparatus comprising:

• a memory configured to store a current block of video data;
• and
• one or more processors in communication with the memory, wherein the apparatus is configured to:
• receive the current block of video data that is to be encoded using affine motion compensation;
• construct an affine motion vector predictor (MVP) list for a plurality of control points of an affine model used to code the current block of video data, including adding a motion vector from a neighboring block of video data to the affine MVP list as a motion vector predictor based on the motion vector having an associated reference picture that is the same as a target reference picture for the current block of video data, and refraining from adding the motion vector from the neighboring block of video data to the affine MVP list as a motion vector predictor based on the motion vector not having the associated reference picture that is the same as the target reference picture for the current block of video data,
• wherein to construct the affine MVP list, the apparatus is further configured to derive a single candidate from a plurality of motion vector predictors, wherein the plurality of motion vector predictors includes a first motion vector predictor (MVP0), a second motion vector predictor (MVP1), and a third motion vector predictor (MVP2) based on the affine model being a 6-parameter affine model, and wherein the plurality of motion vector predictors includes the first motion vector predictor (MVP0) and the second motion vector predictor (MVP1) based on the affine model being a 4-parameter affine model;
• determine motion vectors for the plurality of control points using the affine MVP list;
• and
• encode the current block of video data with the determined motion vectors for the plurality of control points of the current block of video data.