Warped motion compensation with explicitly signaled extended rotations

A computing device for decoding a current block of a current frame, comprising:

• a processor configured to:
• determine a prediction model of the current block, wherein the processor is configured to determine the prediction model by steps to:
• determine whether to predict the current block using a motion vector, a local warping model, or a global motion model;
• obtain motion parameters of the prediction model;
• decode, from a compressed bitstream, a rotation angle that is explicitly signaled to apply additional rotation to the motion parameters and is separate from the motion parameters;
• obtain a warping matrix by applying the rotation angle to the motion parameters to extend motion compensation beyond a granularity provided by the motion parameters alone;
• and
• obtain, using a warping matrix, a prediction block by projecting the current block to a quadrilateral in a reference frame.

A non-transitory computer-readable storage medium comprising instructions that, when executed by a processor, perform operations for coding a current block, comprising:

• obtaining motion parameters for coding the current block;
• obtaining a rotation angle to apply to the motion parameters that is explicitly signaled in a compressed bitstream, the rotation angle is applied as additional rotation to the motion parameters and is separate from the motion parameters;
• obtaining a warping matrix by applying the rotation angle to the motion parameters to extend motion compensation beyond a granularity provided by the motion parameters alone;
• and
• obtaining, using the warping matrix, a prediction block using the warping matrix.