| CPC H04N 19/137 (2014.11) [H04N 19/105 (2014.11); H04N 19/132 (2014.11); H04N 19/176 (2014.11)] | 6 Claims |
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1. A method for coding a video signal, comprising:
obtaining a first reference picture and a second reference picture associated with a video block;
obtaining first prediction samples of the video block from the first reference picture;
obtaining second prediction samples of the video block from the second reference picture;
obtaining padded prediction samples, and obtaining horizontal and vertical gradient values of the first prediction samples and the second prediction samples based on the padded prediction samples, comprising:
deriving rows and columns of prediction samples outside the video block for the first prediction samples;
deriving rows and columns of prediction samples outside the video block for the second prediction samples; and
obtaining horizontal and vertical gradient values of the first prediction samples and the second prediction samples based on the derived rows and columns of prediction samples,
wherein bit-depths of the horizontal and vertical gradient values are controlled by performing a shift operation according to shift values, wherein the shift values comprise a first shift value for calculation of gradient values that are used in a prediction refinement with optical flow (PROF) process, and
wherein deriving the rows and columns of the prediction samples further comprises:
deriving a first part of prediction samples from integer reference samples in the reference picture that are closest to a fractional sample position in a horizontal direction; and
deriving a second part of prediction samples from integer reference samples in the reference picture that are closest to a fractional sample position in a vertical direction;
obtaining motion refinements for samples in the video block based on the horizontal and vertical gradient values; and
obtaining bi-prediction samples of the video block based on the motion refinements.
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