Transform Block Coding with Context-Bin Constraints
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Solution Overview
Problem
The complexity of syntax coding for transform coefficients in video encoders and decoders, particularly in High Efficiency Video Coding (HEVC) and emerging standards like Versatile Video Coding (VVC, increases processing overhead due to high numbers of context-coded bins, which affects compression efficiency and bitstream parsing throughput.
Innovation Solution
Implementing a method to constrain the maximum number of context-coded bins for transform blocks, switching to bypass mode when the number falls below a threshold, and adapting the coding process based on the size of the region after zero-out or the last significant coefficient group index to reduce the number of coding passes and complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If context-based coding is used for transform coefficients, then compression efficiency is improved, but processing complexity and overhead increase
Solution Approach 1:
The patent dynamically switches between context-based coding and bypass mode based on the remaining number of context-coded bins. When the remaining bins fall below a threshold, the coding mode transitions from context-based to bypass, optimizing the balance between compression efficiency and processing complexity adaptively throughout the encoding process.
Solution Approach 2:
The patent changes the coding parameter (coding mode) based on the state of remaining context-coded bins. By monitoring this parameter and switching modes when thresholds are reached, the system optimizes compression performance while controlling processing complexity through parameter-driven adaptation.
2Measurement precision
If the number of context-coded bins is increased, then coding precision is improved, but processing overhead increases
Solution Approach 1:
The patent applies partial context-based coding by limiting the number of context-coded bins to a maximum threshold. Instead of applying context-based coding to all transform coefficients, it selectively applies it only where beneficial, switching to bypass mode for the remainder, thus achieving sufficient coding precision with reduced processing overhead.
3Device complexity
If TB-level constraint is applied to context-coded bins, then complexity is reduced, but coding flexibility is limited
Solution Approach 1:
The patent segments the transform coefficient coding process into two distinct phases: context-based coding phase and bypass mode phase. This segmentation allows the system to apply complex context-based coding only when beneficial (within TB-level constraints) while using simpler bypass mode for the remainder, reducing overall complexity while maintaining adaptability through phase-based flexibility.
Data Source
AI summary
A method and apparatus for encoding or decoding transform coefficients in a video coding system are disclosed. According to this method, a region after zero-outis determined. A remaining number of context-coded bins is determined for the current TB based on a size of the region after zero-out. The current TB is encoded or decoded using context-based coding with a constraint based on the remaining number of context-coded bins. According to another method, a remaining number of context-coded bins is determined for the current TB based on the last significant CG index.