Adaptive interpolation filter

A video coding device comprising:

• one or more processors configured to:
• determine control points to encode an affine block from a video signal according to affine inter-prediction;
• determine a sub-block size of a sub-block based on the control points for the affine block;
• determine a motion vector for the sub-block of the affine block based on the control points;
• select an interpolation filter for application to a reference block corresponding to the sub-block, the interpolation filter selected based on the sub-block size;
• determine which fractional position at the reference block a motion vector for a current sample points to;
• apply the interpolation filter to the reference block to determine a reference sample at the fractional position;
• determine residual information for the sub-block based on a difference between the current sample of the sub-block and the reference sample at the reference block;
• and
• encode the control points and the residual information in a bitstream.

A method implemented in a decoder, the method comprising:

• receiving, by a receiver of the decoder, a bitstream including control points describing an affine block coded according to affine inter-prediction;
• determining, by one or more processors of the decoder, a sub-block size of a sub-block based on the control points for the affine block;
• determining, by the one or more processors, a motion vector for the sub-block of the affine block based on the control points;
• selecting, by the one or more processors, an interpolation filter for application to a reference block corresponding to the sub-block, the interpolation filter selected based on the sub-block size;
• determining, by the one or more processors, which fractional position at the reference block a motion vector for a current sample points to;
• applying, by the one or more processors, the interpolation filter to the reference block to determine a reference sample at the fractional position;
• determining, by the one or more processors, prediction information based on the reference sample;
• and
• reconstructing, by the one or more processors, the affine block based on the prediction information and based on residual information for the affine block included in the bitstream.

A video coding device comprising:

• a receiver configured to:
• receive a bitstream including control points describing an affine block coded according to affine inter-prediction;
• and
• one or more processors coupled to the receiver and configured to:
• determine a sub-block size of a sub-block based on the control points for the affine block;
• determine a motion vector for the sub-block of the affine block based on the control points;
• select an interpolation filter for application to a reference block corresponding to the sub-block, the interpolation filter selected based on the sub-block size;
• determine which fractional position at the reference block a motion vector for a current sample points to;
• apply the interpolation filter to the reference block to determine a reference sample at the fractional position;
• determine prediction information based on the reference sample;
• and
• reconstruct the affine block based on the prediction information and based on residual information for the affine block included in the bitstream.