Palette-Based Video Coding for Screen Content
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Solution Overview
Problem
Traditional video coding techniques are inefficient for compressing screen-generated content, such as computer graphics, due to its discrete-tone nature and high contrast boundaries, which differ from the continuous-tone and smooth assumptions made in existing methods.
Innovation Solution
Palette-based coding is introduced, where a video coder represents video data using a palette of colors, encoding index values that map pixels to these colors, allowing for efficient compression of screen-generated content by predicting or deriving palettes and encoding them in various modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional video coding techniques are used, then continuous-tone and smooth video content can be encoded, but screen-generated content with discrete-tone and high contrast boundaries cannot be efficiently compressed
Solution Approach 1:
The video block is divided into multiple palette groups, where each group shares a common palette. This segmentation allows the coding method to adapt to different regions with discrete-tone characteristics while maintaining efficiency for continuous-tone areas, resolving the contradiction between compression efficiency and adaptability to screen-generated content.
Solution Approach 2:
The patent introduces palette-based coding parameters including palette size, palette entries, and palette group indices. By changing from traditional pixel-value-based parameters to palette-index-based parameters, the system achieves efficient compression for screen-generated content while maintaining compatibility with traditional video content through configurable palette sizes and groupings.
2Productivity
If palette-based coding is used, then compression efficiency for screen-generated content is improved, but device complexity increases due to palette management
Solution Approach 1:
Multiple palette groups are merged by sharing common palettes. Instead of managing separate palettes for each group, the system combines palette resources so that N groups share M palettes (where M < N), reducing the total number of palettes that need to be transmitted and managed, thus lowering device complexity while maintaining compression efficiency.
Solution Approach 2:
Palettes are copied and reused across multiple palette groups. Rather than creating unique palettes for each group, the system copies existing palettes and assigns them to multiple groups, significantly reducing the amount of palette data that needs to be encoded and decoded, thereby reducing device complexity.
3Measurement precision
If multiple palettes are used for different palette groups, then coding precision is improved, but the amount of data to be transmitted increases
Solution Approach 1:
Redundant palette information is discarded by identifying and removing duplicate palettes across palette groups. The system analyzes palettes from multiple groups, discards duplicates, and recovers the essential unique palette information, thereby maintaining color representation precision while reducing the total data transmission volume.
Solution Approach 2:
Instead of transmitting multiple unique palettes, the system transmits a smaller set of unique palettes and uses copying to reconstruct the full palette set at the decoder. This approach maintains color precision by ensuring all necessary palette entries are available while significantly reducing the quantity of transmitted data.
Data Source
AI summary
In an example, a method of coding video data includes determining, by a video coder and for a block of video data, a palette having a plurality of entries indicating a plurality of respective color values, wherein a first line of the block of video data includes a pixel located adjacent to an edge of the block of video data, and wherein a second line of the block of video data includes a pixel located adjacent to the edge of the block and adjacent to the pixel of the first line. In this example, the method also includes coding, in a scan order, index values that map pixels of the block to entries in the palette, wherein the pixel of the second line immediately follows the pixel of the first line in the scan order.