Patent ID: 11882289
Assignee: LG ELECTRONICS INC.
Field: Audio-visual technology (Electrical engineering)
Classification: CPC H | IPC H

Claim 0:
1. An image decoding method performed by a decoding apparatus, the method comprising:
deriving transform coefficients for a current block based on residual information;
determining whether a significant coefficient exists in a second region other than a first region at a top-left of the current block;
parsing a Low Frequency Non-Separable Transform (LFNST) index from a bitstream based on the determination that the significant coefficient does not exist in the second region;
deriving prediction samples for the current block;
deriving modified transform coefficients by applying an LFNST matrix derived based on the LFNST index to transform coefficients in the first region;
deriving residual samples for the current block based on an inverse primary transform for the modified transform coefficients; and
generating a reconstructed picture based on the residual samples and the prediction samples for the current block,
wherein based on a size of the current block being 4×4, the first region to which the LFNST matrix is applied is from the top-left of the current block to an 8th sample position in a scan order,
wherein based on the size of the current block being 8×8, the first region to which the LFNST matrix is applied is from the top-left of the current block to the 8th sample position in the scan order, and
wherein based on one of the width or height of the current block being greater than 4 and the other of the width or height of the current block being 4, the first region to which the LFNST matrix is applied is a top-left 4×4 area of the current block.