US 12,445,617 B2
Image decoding method using chroma quantization parameter, and apparatus therefor
Jie Zhao, Seoul (KR); Seethal Paluri, Seoul (KR); and Seunghwan Kim, Seoul (KR)
Assigned to LG Electronics Inc., Seoul (KR)
Appl. No. 17/629,957
Filed by LG Electronics Inc., Seoul (KR)
PCT Filed Aug. 20, 2020, PCT No. PCT/KR2020/011085
§ 371(c)(1), (2) Date Jan. 25, 2022,
PCT Pub. No. WO2021/034116, PCT Pub. Date Feb. 25, 2021.
Claims priority of provisional application 62/890,604, filed on Aug. 22, 2019.
Prior Publication US 2022/0264098 A1, Aug. 18, 2022
Int. Cl. H04N 19/132 (2014.01); H04N 19/176 (2014.01); H04N 19/18 (2014.01); H04N 19/186 (2014.01); H04N 19/46 (2014.01); H04N 19/70 (2014.01)
CPC H04N 19/132 (2014.11) [H04N 19/176 (2014.11); H04N 19/18 (2014.11); H04N 19/186 (2014.11); H04N 19/46 (2014.11); H04N 19/70 (2014.11)] 3 Claims
OG exemplary drawing
 
1. An image decoding method performed by a decoding apparatus, the method comprising:
obtaining residual information for a chroma component of a current coding unit;
obtaining Coding Unit (CU) chroma Quantization Parameter (QP) offset related information for the current coding unit based on a tree type and a size of the current coding unit;
deriving transform coefficients for the current coding unit based on the residual information;
deriving a chroma QP for the current coding unit based on the CU chroma QP offset related information;
deriving residual samples for the current coding unit by dequantizing the transform coefficients based on the chroma QP; and
generating a reconstructed picture based on the residual samples,
wherein the CU chroma QP offset related information is obtained in a transform unit syntax for a first transform block which is a first decoded transform block among transform blocks of the current coding unit,
wherein, based on (i) at least one of a width or a height of the current coding unit being greater than 64 and (ii) the tree type being not a dual tree luma, the CU chroma QP offset related information is obtained,
wherein the CU chroma QP offset related information includes a CU chroma QP offset index and a CU chroma QP offset flag for the current coding unit, and
wherein the CU chroma QP offset index is obtained based on the CU chroma QP offset flag indicating that an entry in a CU QP offset list is used to determine a value of a CU chroma QP offset.