Palette Coding Quantization Parameter Management
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Solution Overview
Problem
The existing high efficiency video coding (HEVC) scheme for compressing and recording moving images faces inefficiencies due to the use of a single quantization parameter for both escape coding in palette coding and prediction coding, which fails to effectively control pixel values and transform coefficients, leading to decreased coding efficiency.
Innovation Solution
An image decoding and coding apparatus that determines whether a block is palette-coded or prediction-coded and uses different quantization parameters for escape coding and prediction coding, respectively, to adaptively control the quantization process, thereby improving coding efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single quantization parameter is used for both escape coding and prediction coding, then device complexity is reduced, but coding efficiency deteriorates
Solution Approach 1:
The patent segments the quantization parameter management into two distinct parameters: one for escape coding (QpEscape) and one for prediction coding (Qp). This allows each coding mode to use the most appropriate quantization parameter independently, resolving the contradiction between device complexity and coding efficiency by organizing the system into specialized sub-components.
Solution Approach 2:
The patent applies local quality by allowing different quantization parameters to be used in different coding contexts. Escape-coded pixels use QpEscape while prediction-coded blocks use Qp, enabling each local region to be optimized for its specific coding requirements rather than using a uniform approach throughout.
2Productivity
If different quantization parameters are used for escape coding and prediction coding, then coding efficiency is improved, but device complexity increases
Solution Approach 1:
The patent introduces an intermediary mechanism (the QpEscape derivation process) that automatically generates the escape coding quantization parameter based on the prediction coding quantization parameter and escape coding strength. This mediator handles the complexity of managing two parameters, allowing the system to benefit from differentiated quantization while minimizing the operational burden through automated parameter derivation.
3Device complexity
If pixel values are quantized using a quantization parameter optimized for transform coefficients, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent applies parameter changes by adjusting the quantization parameter specifically for escape coding based on the characteristics of pixel values versus transform coefficients. The QpEscape parameter is derived to account for the different statistical properties and value ranges of pixel data compared to transform coefficients, ensuring optimal quantization precision for each data type.
Data Source
AI summary
An image decoding apparatus decodes a bit stream generated by coding an image and decodes coded data included in the bit stream and corresponding to a target block to be decoded in the image. The apparatus includes a first determining unit configured to determine whether the target block is prediction-coded or palette-coded; a second determining unit configured to determine whether or not a pixel in the target block is escape-coded if the first determining unit determines that the target block is palette-coded; and a first decoding unit configured to decode the target block by using a second quantization parameter different from a first quantization parameter if the second determining unit determines that the pixel is escape-coded. The first quantization parameter is used to decode the coded data in a case where the first determining unit determines that the target block is prediction-coded.