Patent ID: 11902530
Assignee: LG ELECTRONICS INC.
Field: Audio-visual technology (Electrical engineering)
Classification: CPC H | IPC H

Claim 6:
7. An image encoding method performed by an encoding apparatus, the method comprising:
deriving an intra prediction mode for a chroma block as a cross-component linear model (CCLM) mode;
deriving prediction samples for the chroma block based on the CCLM mode;
deriving residual samples for the chroma block based on the prediction samples; and
performing an LFNST to derive transform coefficients;
wherein the performing of the LFNST comprising:
updating the intra prediction mode for the chroma block based on an intra prediction mode for a luma block corresponding to the chroma block;
modifying the updated intra prediction mode to a wide angle intra prediction mode based on a width of the chroma block not being equal to a height of the chroma block;
determining an LFNST set comprising LFNST matrices based on a modified intra prediction mode by the wide angle intra prediction mode mapping process; and
performing a matrix operation based on one LFNST matrix,
wherein the updated intra prediction mode is derived as an intra prediction mode corresponding to a specific position in the luma block,
wherein the specific position is set to ((xTbY+(nTbW*SubWidthC)/2), (yTbY+(nTbH *SubHeightC)/2)),
wherein xTbY and yTbY denote top-left coordinates of the luma block,
wherein nTbW and nTbH denote the width and the height of the chroma block, and
wherein SubWidthC and SubHeightC denote variables corresponding to a color format.