Chroma QP Offset Signaling by Tree Type in Image Decoding
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Solution Overview
Problem
The increasing demand for high-resolution and high-quality images leads to higher transmission and storage costs due to the increased amount of information, necessitating a more efficient image compression technique.
Innovation Solution
An image decoding method that derives a chroma quantization parameter (QP) offset based on the tree type and size of a current chroma block, allowing for efficient signaling of CU chroma QP offset information in transform unit syntax, even when the first transform block has no non-zero coefficients, thereby reducing decoding apparatus costs and buffer requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If chroma QP offset information is signaled only when the first transform block has non-zero coefficients, then transmission efficiency is improved, but decoding apparatus cost and buffer requirements increase
Solution Approach 1:
The patent applies preliminary action by signaling the chroma QP offset information in advance at the transform unit level, before the decoding apparatus needs to process the transform blocks. This allows the decoding apparatus to have the necessary information ready beforehand, eliminating the need for complex conditional logic and buffer management to handle cases where information might be missing.
Solution Approach 2:
The patent segments the chroma block into transform units and signals QP offset information at each transform unit level independently. This segmentation allows the decoding apparatus to process each transform unit with its own QP offset information, simplifying the overall decoding process and reducing buffer requirements compared to handling the entire chroma block as a single unit.
2Device complexity
If chroma QP offset information is always signaled regardless of non-zero coefficients, then decoding apparatus cost is reduced, but transmission efficiency decreases
Solution Approach 1:
The patent applies local quality by signaling chroma QP offset information selectively at the transform unit level based on local characteristics. Each transform unit can have its own QP offset information signaled in its syntax, allowing the system to adapt to local variations in the image data while maintaining a simple decoding structure. This avoids both extremes of always signaling or never signaling the information.
Data Source
AI summary
An image decoding method performed by a decoding apparatus, according to the present document, comprises the steps of: obtaining residual information for a current chroma block; obtaining CU chroma QP offset-related information for the current chroma block on the basis of the size and tree type of the current chroma block; deriving transform coefficients for the current chroma block on the basis of the residual information; deriving chroma QP for the current chroma block on the basis of the CU chroma QP offset-related information; deriving residual samples for the current chroma block by dequantizing the transform coefficients on the basis of the chroma QP; and generating a reconstructed picture on the basis of the residual samples.