Palette Coding for Screen Content Video Compression
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Solution Overview
Problem
Existing video compression methods are inefficient for screen content, leading to poor compression performance and quality issues, such as blurred curves and texts, due to their failure to fully characterize the features of screen content, which is prevalent in media presentations and remote desktop applications.
Innovation Solution
The use of palette decoding techniques, including palette index prediction and BWT-based palette index map reordering, to efficiently encode screen content by creating a palette table and index map that maps pixels to color indices, reducing redundancy and improving compression efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If existing video compression methods are used for screen content, then general video compression is achieved, but compression performance is inefficient and quality is poor with blurred curves and texts
Solution Approach 1:
The patent segments screen content into discrete color palettes and represents the content using palette indices rather than full color values. This segmentation approach separates the color information (palette) from the spatial information (index map), enabling more efficient compression while preserving sharp edges and text clarity.
Solution Approach 2:
The patent transforms the representation parameters of screen content from direct color values to palette indices. By changing the parameter space from continuous color values to discrete index values, the method achieves better compression efficiency while maintaining the sharpness of text and graphical elements.
2Productivity
If block coding modes and transform are used for screen content encoding, then video coding is performed, but bandwidth consumption increases
Solution Approach 1:
The patent uses run-length encoding to copy repeated palette indices without transmitting them individually. Consecutive pixels with the same color index are represented by a single index value and a run length, significantly reducing the data volume and bandwidth consumption for screen content with large uniform areas.
3Productivity
If palette decoding techniques are used, then compression efficiency is improved and bandwidth consumption is reduced, but device complexity increases
Solution Approach 1:
The patent performs preliminary palette extraction and organization before the main encoding process. By pre-processing the screen content to identify and store the palette table, the actual encoding process becomes simpler, as it only needs to generate index maps rather than process full color information.
Solution Approach 2:
The patent introduces a palette table as an intermediary data structure between the original screen content and the compressed representation. This intermediary allows the encoder to work with simplified index values while maintaining the ability to reconstruct the original content, reducing overall system complexity.
Data Source
AI summary
Video data may be palette decoded. Data defining a palette table may be received. The palette table may comprise index values corresponding to respective colors. Palette index prediction data may be received and may comprise data indicating index values for at least a portion of a palette index map mapping pixels of the video data to color indices in the palette table. The palette index prediction data may comprise run value data associating run values with index values for at least a portion of a palette index map. A run value may be associated with an escape color index. The palette index map may be generated from the palette index prediction data at least in part by determining whether to adjust an index value of the palette index prediction data based on a last index value. The video data may be reconstructed in accordance with the palette index map.