Scaling List Determination for Adaptive Color Transform in Video Encoding
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Solution Overview
Problem
The adaptive color transform (ACT) technique in VVC can cause visual deterioration in image quality due to the application of scaling lists designed for luminance components to chrominance components, leading to inconsistent quantization processes across different color components.
Innovation Solution
The encoding and decoding devices employ a uniform scaling list when ACT is applied, ensuring consistent quantization across all components, thereby minimizing image quality deterioration when encoding and decoding videos with both ACT-applied and non-ACT-applied blocks coexist.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If scaling lists designed for luminance components are applied to chrominance components during ACT, then encoding efficiency is improved, but image quality deteriorates due to inconsistent quantization processes
Solution Approach 1:
The patent applies different scaling list determination strategies based on the color component type. For luminance components, traditional scaling lists are used to maintain encoding efficiency. For chrominance components during ACT, uniform scaling lists are applied to ensure consistent quantization and prevent visual deterioration. This localized adaptation resolves the contradiction by optimizing each component type according to its specific requirements.
Solution Approach 2:
The patent changes the scaling list parameters based on the color space transform state. When ACT is applied, the scaling list parameters for chrominance components are modified to use uniform values across all frequency regions, rather than the traditional frequency-dependent scaling. This parameter change ensures consistent quantization for chrominance components while maintaining encoding efficiency for luminance components.
2Adaptability or versatility
If different scaling lists are applied to different color components, then quantization can be optimized for each component, but inconsistency arises when ACT-applied and non-ACT-applied blocks coexist
Solution Approach 1:
The patent introduces dynamic scaling list selection based on the ACT application state. The scaling list configuration changes dynamically depending on whether ACT is applied to the current block. When ACT is applied, uniform scaling lists are used for chrominance components; when ACT is not applied, traditional component-specific scaling lists are used. This dynamic adaptation maintains both optimality and consistency.
Solution Approach 2:
The patent makes the uniform scaling list serve multiple functions: it acts as the scaling list for chrominance components during ACT, and also ensures consistency across blocks with different ACT application states. This universal application of uniform scaling lists for chrominance during ACT resolves the inconsistency issue while maintaining quantization optimization through context-aware selection.
Data Source
AI summary
An encoding device encodes each encoding-target block. The encoding device includes: a predictor configured to generate, for each of the components, a prediction block corresponding to the encoding-target block; a residual generator configured to generate, for each of the components, a prediction residual that represents a difference between the encoding-target block and the prediction block; a color space transformer configured to perform a color space transform process on the prediction residual of each of the components; a transformer configured to generate transform coefficients by performing a transform process on the prediction residual; a quantization controller configured to determine a scaling list to be used in a quantization process on the transform coefficients; and a quantizer configured to perform the quantization process on the transform coefficients by using the determined scaling list, wherein the quantization controller is configured to determine the scaling list, based on the color space transform process.