Patent ID: 11936885
Assignee: NIPPON HOSO KYOKAI
Field: Audio-visual technology (Electrical engineering)
Classification: CPC H | IPC H

Claim 2:
3. A decoding method for performing a decoding process on a block obtained by dividing an original image including a plurality of color components, the method comprising:
decoding a bitstream and thereby outputting
transform coefficients being for each color component of the block,
a first flag indicating for each color component whether the block includes a non-zero transform coefficient, and
a second flag indicating whether a prediction residual transform process is applied to the block, the prediction residual transform process being a process generating a new prediction residual for each color component by a process using prediction residuals of two or more color components;

performing the prediction residual transform process for the prediction residual restored from the transform coefficients, when the second flag indicates that prediction residual transform process is applied to the block; and
determining whether to perform chroma residual scaling for the prediction residual of the chrominance component, based on the first flag of a chrominance component and the second flag, the chroma residual scaling performs scaling based on a luminance component corresponding to the chrominance component, wherein
the determining whether to perform chroma residual scaling comprises determining not to perform the chroma residual scaling when the first flag indicates that a block of the chrominance component does not include a non-zero transform coefficient and the second flag indicates that the block has not been encoded using the color space transform.