Patent ID: 11882273
Assignee: LG ELECTRONICS INC.
Field: Audio-visual technology (Electrical engineering)
Classification: CPC H | IPC H

Claim 0:
1. A method for decoding an image performed by a decoding apparatus, comprising:
determining a secondary transform set among a pre-determined number of secondary transform sets based on an intra prediction mode of a current block;
obtaining a first syntax element related to a secondary transform matrix to be applied to the current block among secondary transform matrices included in the secondary transform set;
performing a secondary inverse-transform on secondary transformed coefficients of the current block based on the secondary transform matrix specified by the first syntax element to obtain primary transformed coefficients, the secondary inverse-transform being a non-separable transform;
performing a primary inverse-transform on the primary transformed coefficients based on a primary transform matrix of the current block to obtain residual samples of the current block; and
generating reconstructed samples of the current block based on the residual samples,
wherein a number of input coefficients of the secondary inverse-transform and a number of output coefficients of the secondary inverse-transform are respectively determined as 8 and 16 based on the current block having a 4×4 size, and
wherein the number of the input coefficients of the secondary inverse-transform for the current block having the 4×4 size is equal to the number of the input coefficients of the secondary inverse-transform for the current block having an 8×8 size, while the number of the output coefficients of the secondary inverse-transform for the current block having the 4×4 size is not equal to the number of the output coefficients of the secondary inverse-transform for the current block having the 8×8 size.