Context Selection for Video Transform Coefficients
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Solution Overview
Problem
Existing video encoding and decoding techniques face challenges in achieving efficient compression while maintaining low distortion, particularly in advanced video codecs like VVC and HEVC.
Innovation Solution
The proposed solution involves a video coder configured to code syntax elements indicating the absolute value of transform coefficients in a block, using a significance flag and multiple greater_than_N flags, and determining contexts for these syntax elements from context tables to improve coding efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional video encoding techniques are used, then the encoding process is simple, but compression efficiency is insufficient and distortion is high
Solution Approach 1:
The patent segments the transform coefficient coding process into multiple stages using significance flags and greater-than-N flags. Each flag represents a decision point in the coding process, allowing the encoder to process coefficients in a structured, segmented manner that improves compression efficiency while maintaining manageable complexity through systematic processing steps.
Solution Approach 2:
The patent implements dynamic context selection where the coding strategy adapts based on the values of significance flags and greater-than-N flags. The context tables are dynamically updated based on the coding process, allowing the system to adjust its behavior in real-time to optimize compression efficiency for different video content characteristics.
2Productivity
If more sophisticated coding models are used, then compression efficiency improves, but the complexity of the coding process increases
Solution Approach 1:
The patent changes parameters such as the thresholds N in greater-than-N flags and the structure of context tables to optimize compression efficiency. By adjusting these parameters and using different context table configurations, the system can adapt the coding model complexity to achieve better compression without requiring overly complex algorithms.
Solution Approach 2:
The patent introduces context tables as intermediary structures that mediate between the transform coefficients and the final encoded data. These context tables organize and facilitate the coding process, making the complex coding model more manageable and efficient by providing a structured intermediary layer for processing.
3Measurement precision
If transform coefficients are encoded with high precision, then coding accuracy is high, but the bit rate increases
Solution Approach 1:
The patent applies partial action by using significance flags to indicate only when transform coefficients are non-zero, and greater-than-N flags to provide selective precision information. This partial coding approach maintains sufficient coding accuracy for most applications while reducing the overall bit rate by avoiding unnecessary precision for coefficients that are zero or very small.
Solution Approach 2:
The patent changes the precision parameters dynamically through the greater-than-N flags, where N can be adjusted based on the importance and magnitude of transform coefficients. This allows the system to allocate higher precision only where needed, maintaining coding accuracy for significant coefficients while using lower precision for less important ones, thereby reducing the overall bit rate.
Data Source
AI summary
A video coder may be configured to code a plurality of syntax elements that indicate an absolute value of a transform coefficients in a block, wherein the plurality of syntax elements include a significance flag and four or more greater_than_N flags. The video coder may further determine first respective contexts for each syntax element in a first set of the plurality of syntax elements from respective context tables for each syntax element in the first set of the plurality of syntax elements, and determine second respective contexts for each syntax element in a second set of the plurality of syntax elements from a shared context table.