Patent ID: 11936911
Assignee: LG ELECTRONICS INC.
Field: Audio-visual technology (Electrical engineering)
Classification: CPC H | IPC H

Claim 3:
4. A transmission method of data for an image, the method comprising:
obtaining a bitstream for the image, wherein the bitstream is generated based on deriving prediction samples based on an intra prediction mode applied to a target block, deriving residual samples for the target block based on the prediction samples, deriving transform coefficients for the target block based on a primary transform for the residual samples, deriving modified transform coefficients based on a secondary transform of the transform coefficients, deriving quantized transform coefficients based on a quantization of the modified transform coefficients, and encoding prediction information, information on the quantized transform coefficients, and a transform index related to a transform kernel matrix; and
transmitting the data comprising the bitstream,
wherein the deriving of the modified transform coefficients comprises:
determining a transform set and the transform kernel matrix, and
performing a matrix operation of the transform coefficients and the transform kernel matrix,

wherein the transform index that represents at least one of first index information, second index information, and third index information, the first index information indicating the inverse secondary transform being not applied to the target block, the second index information indicating a first transform kernel matrix as the transform kernel matrix for the inverse secondary transform, and the third index information indicating a second transform kernel matrix as the transform kernel matrix for the inverse secondary transform,
wherein the transform set is determined based on the intra prediction mode of the target block,
wherein the intra prediction mode of the target block is mapped to one of the four transform sets,
wherein the transform set is determined, based on the intra prediction mode being equal to 0 or 1, as a first transform set index value,
wherein the transform set is determined, based on the intra prediction mode being greater than or equal to 2 and smaller than or equal to 12, as a second transform set index value,
wherein the transform set is determined, based on the intra prediction mode being greater than or equal to 13 and smaller than or equal to 23, as a third transform set index value,
wherein the transform set is determined, based on the intra prediction mode being greater than or equal to 24 and smaller than or equal to 44, as a fourth transform set index value,
wherein the transform set is determined, based on the intra prediction mode being greater than or equal to 45 and smaller than or equal to 55, as the third transform set index value, and
wherein the transform set is determined, based on the intra prediction mode being greater than or equal to 56, as the second transform set index value.