Arithmetic decoding context index derivation for transform coefficients
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Solution Overview
Problem
The existing video coding and decoding technologies do not sufficiently reduce the processing amount related to coding and decoding of transform coefficients.
Innovation Solution
An arithmetic decoding device and an arithmetic coding device that decode and encode transform coefficients by deriving context indices based on sub-block coefficient presence/absence flags, reducing the processing amount by utilizing adjacent sub-block flags to determine context indices for efficient decoding and encoding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If context-based adaptive binary arithmetic coding (CABAC) is used to code transform coefficients, then coding precision is improved, but processing complexity increases
Solution Approach 1:
The frequency region is divided into multiple partial regions, and different context index derivation methods are applied to different regions. Low-frequency components use position-based contexts, intermediate-frequency components use neighbor reference contexts, and high-frequency components use fixed contexts, thereby segmenting the complex coding process into manageable parts.
Solution Approach 2:
Different context index derivation strategies are applied to different frequency regions based on their local characteristics. Low-frequency regions use one method, intermediate-frequency regions use another, and high-frequency regions use a third method, optimizing the balance between precision and complexity for each local region.
2Measurement precision
If the number of context indices is increased to improve coding accuracy, then coding precision is improved, but device complexity increases
Solution Approach 1:
The context index derivation method changes based on the frequency component's position and the block size. By dynamically selecting different derivation methods (position-based, neighbor reference, or fixed) according to the parameters of the frequency region, the system achieves high coding accuracy without requiring an excessive number of context indices.
3Manufacturing precision
If transform coefficients are coded in detail to improve image quality, then manufacturing precision is improved, but processing time increases
Solution Approach 1:
The frequency region is segmented into partial regions with different coding strategies. Low-frequency components that contribute most to image quality receive detailed coding with position-based contexts, while high-frequency components use simpler fixed contexts, reducing overall processing time while maintaining image quality.
Solution Approach 2:
The patent applies detailed context-based coding only where necessary (low and intermediate frequency regions), while using simpler fixed contexts for high-frequency regions where detailed coding provides diminishing returns. This partial application of complex coding strategies reduces processing time while maintaining acceptable image quality.
Data Source
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AI summary
To reduce the amount of processing related to coding and decoding of transform coefficients, a sub-block coefficient presence/absence flag indicating whether or not at least one non-zero transform coefficient is included is decoded for each of two or more sub-blocks obtained by dividing a unit region, and a context index of a target sub-block is derived on the basis of transform coefficient presence/absence flags each indicating whether or not a transform coefficient is 0. In accordance with the sub-block coefficient presence/absence flags of adjacent sub-blocks that are adjacent to the target sub-block, the context index of the target sub-block is derived.