Patent ID: 11949873
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:
obtaining residual information from a bitstream;
deriving transform coefficients for a current block based on the residual information; and
deriving residual samples for the current block by applying an inverse primary transform to the transform coefficients based on a multiple transform selection (MTS) index;
wherein the deriving of the transform coefficient comprises:
deriving whether a significant coefficient is present in a scan subblock by scanning the scan subblock in a preset scan subblock unit according to an reverse diagonal scan order; and
deriving flag information indicating whether the significant coefficient is present in a second region based on (i) whether the significant coefficient is present the scan subblock, (ii) whether the scan subblock belongs to the second region other than a top-left 16×16 region of the current block, and (iii) whether a color index of the current block is 0, and
the MTS index is parsed based on the flag information indicating that the significant coefficient is not present in the second region.