Escape Sample Coding in Palette-Based Video Compression
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Solution Overview
Problem
Traditional video coding techniques are inefficient for compressing screen-generated content with discrete-tone and high contrast features, as they assume continuous-tone and smoothness, leading to suboptimal compression performance in applications like remote desktop and wireless display.
Innovation Solution
Palette-based coding techniques are employed, where a video coder represents video data using a 'palette' of colors, encoding pixel indices rather than actual pixel values, suitable for areas with a small number of colors, and can be integrated with existing standards like HEVC, allowing for inter- and intra-predictive coding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional video coding techniques are used, then continuous-tone and smoothness assumptions are made, but compression efficiency deteriorates for screen-generated content with discrete-tone and high contrast features
Solution Approach 1:
The patent changes the fundamental parameter of color representation from continuous pixel values to discrete palette indices. By transforming the color space from continuous to discrete, the coding system becomes adapted to screen-generated content characteristics, improving compression efficiency while maintaining coding performance reliability.
Solution Approach 2:
The patent segments the color space into discrete palette entries rather than using continuous color values. This segmentation allows the system to represent screen content with limited colors more efficiently, addressing the contradiction between compression efficiency and coding performance for discrete-tone content.
2Productivity
If palette-based coding is used for screen-generated content, then compression efficiency improves, but device complexity increases due to additional signaling requirements
Solution Approach 1:
The patent extracts and removes redundant signaling information by using implicit escape coding. When a palette index exceeds the number of defined palette entries, the system automatically uses escape coding without requiring additional explicit flags or signaling, thus reducing device complexity while maintaining compression efficiency.
Solution Approach 2:
The coding system performs self-service by automatically handling out-of-bounds palette indices through implicit escape coding. The decoder can identify and process escape codes without additional signaling, allowing the system to manage its own complexity and reduce the burden on external signaling mechanisms.
Data Source
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AI summary
In an example, a method of processing video data includes determining a value of a block-level syntax element that indicates, for all samples of a block of video data, whether at least one respective sample of the block is coded based on a color value of the at least one respective sample not being included in a palette of colors for coding the block of video data. The method also includes coding the block of video data based on the value.