	US 11,997,281 B2
	Image decoding method for coding chroma quantization parameter data, and device for same
Seethal Paluri, Seoul (KR); Seunghwan Kim, Seoul (KR); and Jie Zhao, Seoul (KR)
Assigned to LG Electronics Inc., Seoul (KR)
Appl. No. 17/624,993
Filed by LG Electronics Inc., Seoul (KR)
PCT Filed Jul. 3, 2020, PCT No. PCT/KR2020/008734 § 371(c)(1), (2) Date Jan. 5, 2022, PCT Pub. No. WO2021/006558, PCT Pub. Date Jan. 14, 2021.
Claims priority of provisional application 62/871,063, filed on Jul. 5, 2019.
Prior Publication US 2022/0303542 A1, Sep. 22, 2022
Int. Cl. H04N 19/00 (2014.01); H04N 19/132 (2014.01); H04N 19/172 (2014.01); H04N 19/186 (2014.01); H04N 19/46 (2014.01); H04N 19/70 (2014.01)

CPC H04N 19/132 (2014.11) [H04N 19/172 (2014.11); H04N 19/186 (2014.11); H04N 19/46 (2014.11); H04N 19/70 (2014.11)]

4 Claims

1. An image decoding method, performed by a decoding apparatus, the method comprising:

obtaining (i) a flag for whether one chroma Quantization Parameter (QP) mapping table is signaled and applied for chroma components including a Cb component, a Cr component, and a joint CbCr component and (ii) a joint CbCr enable flag;

obtaining chroma quantization parameter data of at least one chroma QP mapping table for the chroma components based on the flag and the joint CbCr enable flag;

deriving the chroma QP mapping table based on the chroma quantization parameter data;

deriving a chroma quantization parameter for the chroma components based on the chroma QP mapping table;

deriving residual samples for the chroma components based on the chroma quantization parameter; and

generating a reconstructed picture based on the residual samples,

wherein, based on a value of the flag being equal to 1, the one chroma QP mapping table is signaled and applied for the Cb component, the Cr component, and the joint CbCr component,

wherein, based on the value of the flag being equal to 0 and a value of the joint CbCr enable flag being equal to 1, two chroma QP mapping tables for the Cb component and the Cr component are signaled and the chroma QP mapping table for the joint CbCr component is additionally signaled, and

wherein, based on the value of the flag being equal to 0 and the value of the joint CbCr enable flag being equal to 0, the two chroma QP mapping tables for the Cb component and the Cr component are signaled and the chroma QP mapping table for the joint CbCr component is not signaled.