Video Transform Quantization Switching for Coefficient Correlation Coding
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Solution Overview
Problem
Conventional scalar quantization independently processes each transform coefficient, reducing the effectiveness of subsequent entropy coding and overall encoding efficiency due to failure to exploit correlations between coefficients.
Innovation Solution
Implement trellis coded quantization (TCQ) to generate quantization indices that account for entropy coding efficiency by evaluating different permutations based on a cost function, allowing for increased compression opportunities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If scalar quantization is used to independently process each transform coefficient, then the processing complexity is reduced, but the encoding efficiency and compression effectiveness are deteriorated due to failure to exploit correlations between coefficients
Solution Approach 1:
The patent merges multiple transform coefficients into groups and processes them collectively using trellis coded quantization instead of independently processing each coefficient. This combining approach exploits correlations between coefficients while maintaining manageable processing complexity through structured grouping and state-machine-based quantization.
Solution Approach 2:
The patent introduces dynamic state transitions in the trellis coded quantization process, where the quantization of each coefficient depends on the state carried from previous coefficients in the group. This dynamic approach adapts to local correlations in the data, improving encoding efficiency without requiring exhaustive search of all possible quantization combinations.
2Ease of manufacture
If scalar quantization is applied to each transform coefficient independently, then the quantization process is simplified, but the effectiveness of subsequent entropy coding is reduced
Solution Approach 1:
The patent performs preliminary grouping of transform coefficients and applies trellis coded quantization that anticipates the needs of subsequent entropy coding. By organizing coefficients into groups and processing them with state transitions before entropy coding, the method prepares the data in a form that maximizes compression effectiveness while keeping the quantization process systematically simple.
Solution Approach 2:
The trellis coded quantization process uses feedback through state transitions, where the quantization decision for each coefficient influences the state for the next coefficient in the group. This feedback mechanism ensures that quantization decisions are made with awareness of correlations, improving entropy coding effectiveness without significantly complicating the overall process.
3Productivity
If trellis coded quantization is implemented to account for correlations between transform coefficients, then the encoding efficiency is improved, but the processing complexity increases
Solution Approach 1:
The patent segments transform coefficients into manageable groups for trellis coded quantization processing. By dividing the full set of coefficients into smaller groups, the method captures local correlations within each group while keeping the computational complexity of the trellis process bounded and tractable, thus improving encoding efficiency without excessive complexity increase.
Solution Approach 2:
The patent changes the quantization parameter structure by using state variables in the trellis coded quantization process. Instead of independent quantization parameters for each coefficient, the method uses a shared state parameter that evolves through the group, reducing the effective number of independent parameters and managing complexity while capturing correlations.
Data Source
AI summary
In various embodiments, an encoder receives transform coefficients of prediction residues associated with video data. The encoder sets a flag value based on at least one of metadata or transform statistics associated with a vector of the transform coefficients. The encoder performs trellis coded quantization operations on the vector of the transform coefficients to generate a vector of quantization indices or one or more scalar quantization operations on the transform coefficients to generate a set of quantization indices based on the flag value. The encoder performs entropy coding operations on either the vector of quantization indices or a vector corresponding to the set of quantization indices to generate encoded video data.