Method and apparatus for video coding

An apparatus for video decoding, comprising:

• processing circuitry configured to:
• decode prediction information of a current block in a current picture from a coded video bitstream, the prediction information being indicative of an affine merge model, the current block including control points;
• determine a first candidate control point motion vector (CPMV) for a first control point of the control points based on one of (i) at least two CPMVs of a first neighboring block of the first control point and (ii) a translational motion vector (MV) of a second neighboring block of the first control point;
• derive affine merge candidates for the current block based on candidate CPMVs for the control points of the current block, the candidate CPMVs of the control points including the first candidate CPMV;
• determine parameters of the affine merge model based on one of the affine merge candidates, the one of the affine merge candidates being defined according to the prediction information, the parameters of the affine merge model being used to transform between the current block and a reference block in a reference picture that has been reconstructed;
• and
• reconstruct at least a sample of the current block according to the affine merge model,
• wherein:
• the prediction information indicates a selection of the affine merge candidates,
• the processing circuitry is further configured to define the one of the affine merge candidates in accordance with the prediction information, and
• the processing circuitry is further configured to:
• determine the first candidate CPMV for the first control point based on at least two CPMVs of a first affine coded block among neighboring blocks of the first control point according to a checking order established for only the first control point and
• determine the first candidate CPMV for the first control point based on a translational MV of a first available block among the neighboring blocks of the first control point according to the checking order, responsive to none of the neighboring blocks of the first control point being affine coded.

A non-transitory computer-readable medium storing instructions which when executed by a computer for video decoding cause the computer to perform:

• decoding prediction information of a current block in a current picture from a coded video bitstream, the prediction information being indicative of an affine merge model, the current block including control points;
• determining a first candidate control point motion vector (CPMV) for a first control point of the control points based on one of (i) at least two CPMVs of a first neighboring block of the first control point and (ii) a translational motion vector (MV) of a second neighboring block of the first control point;
• deriving affine merge candidates for the current block based on candidate CPMVs for the control points of the current block, the candidate CPMVs of the control points including the first candidate CPMV;
• determining parameters of the affine merge model based on one of the affine merge candidates, the one of the affine merge candidates being defined according to the prediction information, the parameters of the affine merge model being used to transform between the current block and a reference block in a reference picture that has been reconstructed;
• and
• reconstructing at least a sample of the current block according to the affine merge mode,
• wherein:
• the prediction information indicates a selection of the affine merge candidates,
• the method further includes defining the one of the affine merge candidates in accordance with the prediction information, and
• the determining the first candidate CPMV for the first control point further comprises one of:
• determining the first candidate CPMV for the first control point based on at least two CPMVs of a first affine coded block among neighboring blocks of the first control point according to a checking order established for only the first control point and
• determining the first candidate CPMV for the first control point based on a translational MV of a first available block among the neighboring blocks of the first control point according to the checking order, responsive to none of the neighboring blocks of the first control point being affine coded.