Method and apparatus of matrix-based intra prediction for video coding
Method and apparatus of video coding are disclosed. According to one method, the left reference boundary samples and the top reference boundary samples are checked jointly. According to another method, selected original left reference boundary samples and selected original top reference boundary samples at specific positions are used for predictor up-sampling. According to yet another method, the horizontal interpolation and the vertical interpolation are in a fixed order regardless of a shape of the current block, size of the current block or both.
1. A method of video coding, the method comprising:
receiving input data related to a current block in a current picture at a video encoder side or receiving a video bitstream comprising coded data of the current block at a video decoder side;
determining a target reference boundary region comprising left reference boundary samples and top reference boundary samples;
deriving a reduced predictor, wherein a process to derive the reduced predictor comprises applying matrix multiplication on a boundary vector and adding an offset, and wherein the boundary vector is derived from the target reference boundary region;
when the reduced predictor is smaller than the current block, performing an up-sampling process on the reduced predictor to generate an up-sampled predictor having a size identical to the current block, wherein the up-sampling process applies horizontal interpolation and vertical interpolation in a fixed order independent of a width and/or a height of the current block; and
encoding or decoding the current block using the up-sampled predictor,
wherein the step of performing the up-sampling process on the reduced predictor comprises:
using one or more original left reference samples for applying the horizontal interpolation; and
after applying the horizontal interpolation, using one or more original top reference samples for applying the vertical interpolation.
2. The method of claim 1 , wherein the horizontal interpolation is always applied before the vertical interpolation.
3. An apparatus of video coding, the apparatus of video coding comprising one or more electronic circuits or processors arranged to:
receive input data related to a current block in a current picture at a video encoder side or receive a video bitstream comprising coded data of the current block at a video decoder side;
determine a target reference boundary region comprising left reference boundary samples and top reference boundary samples;
derive a reduced predictor, wherein a process to derive the reduced predictor comprises applying matrix multiplication on a boundary vector and adding an offset, wherein the boundary vector is derived from the target reference boundary region;
when the reduced predictor is smaller than the current block, performing an up-sampling process on the reduced predictor to generate an up-sampled predictor having a size identical to the current block, wherein the up-sampling process applies horizontal interpolation and vertical interpolation in a fixed order independent of a width and/or a height of the current block; and
encode or decode the current block using the up-sampled predictor,
wherein the step of performing the up-sampling process on the reduced predictor comprises:
using one or more original left reference samples for applying the horizontal interpolation; and
after applying the horizontal interpolation, using one or more original top reference samples for applying the vertical interpolation.