Palette Table and Index Map Coding for Screen Content Compression
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Solution Overview
Problem
Current screen content coding techniques, such as pseudo string match and color palette coding, face challenges in complexity and efficiency, particularly with fixed block decomposition and increased encoder complexity, limiting their performance in lossless and lossy coding modes.
Innovation Solution
The proposed solution involves advanced screen content coding using improved palette table and index map coding methods, including pixel representation, palette table compression, color index map compression, and residual compression, which are integrated with the HEVC Range Extension to enhance coding efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If intra block copy with fixed block decomposition is used, then coding performance is bounded, but device complexity increases significantly
Solution Approach 1:
The patent divides the screen content into multiple layers including a foreground layer and a background layer. Each layer is independently coded with its own palette table and index map, allowing selective processing of different content regions and reducing overall encoding complexity while maintaining coding performance.
Solution Approach 2:
The patent introduces a new dimension of color space representation by using multiple palette tables for different layers instead of a single palette table. This dimensional expansion in color representation allows more efficient coding of diverse screen content without increasing block decomposition complexity.
2Loss of information
If pseudo string match is used for lossless coding, then coding gain is highest, but complexity overhead is significant
Solution Approach 1:
The patent segments the coding process into multiple stages: palette table generation, index map creation, and residual coding. This segmentation allows the lossless pseudo string match technique to be applied selectively to the index map rather than the entire image, reducing complexity overhead while maintaining lossless coding gain.
Solution Approach 2:
The patent applies partial string matching only to the index map data rather than the full image data. This partial action approach achieves most of the lossless coding benefit with significantly reduced computational complexity compared to full image-level string matching.
3Loss of information
If color palette coding is used, then compression efficiency improves for screen content, but performance is limited for continuous color tones
Solution Approach 1:
The patent segments the color representation into multiple palette tables, each optimized for specific content regions or layers. This allows the system to use discrete palette coding for regions with limited colors while maintaining the ability to represent continuous color tones through multiple specialized palettes, improving both compression efficiency and color adaptability.
Solution Approach 2:
The patent creates a composite coding structure that combines multiple palette tables with different color characteristics. This composite approach allows the system to leverage the strengths of palette coding for screen content while extending adaptability to handle continuous color tones through the combination of multiple specialized color tables.
Data Source
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AI summary
An apparatus is configured to perform a method for screen content encoding. The method includes deriving a palette table and a color index map based on a coding unit (CU). The method also includes encoding the palette table and encoding the color index map. The method further includes combining the encoded palette table and the encoded color index map for transmission to a receiver, where the palette table and index map are decoded to reconstruct a pixel block.