Image Coding Context Selection Without Coefficient Counting
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Solution Overview
Problem
Conventional image coding methods, such as those in the HEVC standard, face challenges in reducing processing amounts while maintaining coding efficiency, particularly due to the need to count coefficients with absolute values greater than a threshold, which increases processing requirements and can lead to decreased efficiency.
Innovation Solution
The proposed method employs arithmetic coding for flags indicating whether a target coefficient's absolute value is greater than a threshold, selecting contexts based on the presence of such coefficients in the immediately-prior coefficient block, reducing the need for counting and processing, and adapting binarization parameters accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If coefficient counting is performed to determine context for arithmetic coding, then coding efficiency can be maintained, but processing amount increases
Solution Approach 1:
The patent extracts only the necessary information (presence of coefficients exceeding threshold in immediately-prior block) without performing full coefficient counting. This selective extraction maintains context accuracy for arithmetic coding while significantly reducing processing requirements.
Solution Approach 2:
The patent performs preliminary determination of whether coefficients exceeding the threshold exist in the immediately-prior coefficient block before proceeding with arithmetic coding. This preliminary action prepares the context selection without requiring complete coefficient analysis, reducing overall processing amount.
2Productivity
If context selection is simplified to reduce processing, then processing amount decreases, but coding efficiency deteriorates
Solution Approach 1:
The patent applies local quality by making context selection specific to the immediately-prior coefficient block's characteristics. Instead of using a generic simplified context, the context is locally adapted based on whether coefficients exceeding the threshold were present in the specific prior block, maintaining coding efficiency while reducing processing.
3Measurement precision
If coefficient blocks are processed with detailed context analysis, then coding precision is improved, but device complexity increases
Solution Approach 1:
The patent segments the context analysis to focus only on the immediately-prior coefficient block rather than analyzing all previous blocks. This segmentation maintains coding precision by capturing relevant local context while reducing device complexity by limiting the scope of analysis to a single prior block.
Data Source
AI summary
An image coding method using arithmetic coding. The method includes: performing arithmetic coding on a first flag that indicates whether or not an absolute value of a target coefficient in a target coefficient block is greater than 1; and performing arithmetic coding on a second flag that indicates whether or not the absolute value is greater than 2. In the arithmetic coding on the first flag and the arithmetic coding on the second flag, it is determined whether or not an immediately-prior coefficient block that has been coded immediately prior to the target coefficient block includes a coefficient having an absolute value greater than a threshold value. Based on a result of the determination, respective contexts to be used in the arithmetic coding on the first and second flags are selected.