Patent ID: 11917155
Assignee: LG ELECTRONICS INC.
Field: Audio-visual technology (Electrical engineering)
Classification: CPC H | IPC H

Claim 9:
10. A transmission method for data comprising a bitstream for a picture, comprising:
obtaining the bitstream for the picture, wherein the bitstream is generated by deriving a luma quantization parameter (QP) for a current block, deriving chroma QPs based on a chroma QP mapping table, wherein the chroma QPs include a first chroma QP for a Cb component and a second chroma QP for a Cr component for the current block, generating information related to QP, and encoding image information including the information related to the QP; and
transmitting the data comprising the bitstream,
wherein the information related to the QP includes information related to the luma QP,
wherein the information related to the luma QP includes information on an absolute value of a QP delta value and information on a sign of the QP delta value,
wherein the luma QP is represented based on a predicted luma QP and the QP delta value,
wherein the predicted luma QP is derived based on a first luma QP of a coding unit containing a luma coding block covering (xQg−1, yQg) and a second luma QP of a coding unit containing a luma coding block covering (xQg, yQg−1), wherein (xQg, yQg) represents a top-left sample position of a current quantization group,
wherein the chroma QP mapping table for the chroma QPs is divided into a first chroma QP mapping table for the Cb component and a second chroma QP mapping table for the Cr component,
wherein the first chroma QP mapping table for the Cb component is a separate mapping table from the second chroma QP mapping table for the Cr component,
wherein deriving the chroma QPs comprises:
deriving the first chroma QP for the Cb component based on the luma QP and the first chroma QP mapping table for the Cb component; and
deriving the second chroma QP for the Cr component based on the luma QP and the second chroma QP mapping table for the Cr component, and
wherein both an input of the first chroma QP mapping table and an input of the second chroma mapping table are based on the luma QP.