Method and system for signaling chroma quantization parameter offset

1. A video processing method, comprising:

determining whether a joint CbCr residual coding is enabled, wherein the joint CbCr residual coding codes a same prediction residual for both Cb and Cr components of an image block; and

in response to the joint CbCr residual coding being determined to be enabled, signaling a syntax element for adjusting a quantization parameter (QP) used by the joint CbCr residual coding, the syntax element being signaled in at least one of a Sequence Parameter Set (SPS), a slice header, or an Adaption Parameter Set (APS).

2. The method according to claim 1 , further comprising:

signaling a syntax element for adjusting chroma QP for Cb component at coding unit (CU) level; and

signaling a syntax element for adjusting chroma QP for Cr component at CU level.

3. The method according to claim 1 , wherein the syntax element comprises a chroma QP offset at CU level.

4. The method according to claim 1 , wherein the syntax element is signaled in an SPS, and the method further comprises:

signaling, in the SPS, a flag indicating whether the joint CbCr residual coding is enabled.

5. The method according to claim 1 , wherein the syntax element is signaled in an APS for a target slice of a picture, and the method further comprises:

signaling, in a slice header of the target slice, an identifier pointing to the APS for the target slice.

6. The method according to claim 5 , further comprising:

signaling, in the slice header of the target slice, a flag indicating whether a set of syntax elements for adjusting the QP at CU level are present.

7. The method according to claim 1 , further comprising:

in response to the joint CbCr residual coding being determined to be disabled, signaling a default value for adjusting the QP used by the joint CbCr residual coding.

8. A video processing system, comprising:

a memory configured to store instructions; and

one or more processors coupled to the memory and configured to execute the instructions to cause the system to:

determine whether a joint CbCr residual coding is enabled, wherein the joint CbCr residual coding codes a same prediction residual for both Cb and Cr components of an image block; and

in response to the joint CbCr residual coding being determined to be enabled, signal a syntax element for adjusting chroma quantization parameter (QP) used by the joint CbCr residual coding, the syntax element being signaled in at least one of a Sequence Parameter Set (SPS), a slice header, or an Adaption Parameter Set (APS).

9. The system according to claim 8 , wherein the syntax element is signaled in an SPS, and the one or more processors are further configured to execute the instructions to cause the system to:

signal, in the SPS, a flag indicating whether the joint CbCr residual coding is enabled.

10. The system according to claim 8 , wherein the syntax element is signaled in an APS for a target slice of a picture, and the one or more processors are further configured to execute the instructions to cause the system to:

signal, in a slice header of the target slice, an identifier pointing to the APS for the target slice.

11. The system according to claim 8 , wherein the one or more processors are further configured to execute the instructions to cause the system to:

in response to the joint CbCr residual coding being determined to be disabled, signal a default value for adjusting the QP used by the joint CbCr residual coding.

12. A non-transitory computer-readable storage medium storing a set of instructions that are executable by one or more processors of a device to cause the device to perform:

determining whether a joint CbCr residual coding is enabled, wherein the joint CbCr residual coding codes a same prediction residual for both Cb and Cr components of an image block; and

in response to the joint CbCr residual coding being determined to be enabled, signaling a syntax element for adjusting chroma quantization parameter (QP) used by the joint CbCr residual coding, the syntax element being signaled in at least one of a Sequence Parameter Set (SPS), a slice header, or an Adaption Parameter Set (APS).

13. The non-transitory computer-readable storage medium according to claim 12 , wherein the syntax element is signaled in an SPS, and the set of instructions that are executable by the one or more processors to cause the device to further perform:

signaling, in the SPS, a flag indicating whether the joint CbCr residual coding is enabled.

14. The non-transitory computer-readable storage medium according to claim 12 , wherein the syntax element is signaled in an APS for a target slice of a picture, and the set of instructions that are executable by the one or more processors to cause the device to further perform:

signaling, in a slice header of the target slice, an identifier pointing to the APS for the target slice.

15. The non-transitory computer-readable storage medium according to claim 12 , wherein the set of instructions that are executable by the one or more processors to cause the device to further perform:

in response to the joint CbCr residual coding being determined to be disabled, signaling a default value for adjusting chroma QP for joint CbCr component at CU level.

16. The system according to claim 10 , wherein the one or more processors are further configured to execute the instructions to cause the system to:

signal, in the slice header of the target slice, a flag indicating whether a set of syntax elements for adjusting chroma QP at CU level are present.

17. The non-transitory computer-readable storage medium according to claim 14 , wherein the set of instructions that are executable by the one or more processors to cause the device to further perform:

signaling, in the slice header of the target slice, a flag indicating whether a set of syntax elements for adjusting chroma QP at CU level are present.