Palette Index Map Coding Syntax Grouping
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Solution Overview
Problem
Current palette index map coding techniques in video data compression face inefficiencies in syntax parsing throughput and coding efficiency, particularly in handling palette indices and escape pixels within the HEVC Screen Content Coding standard.
Innovation Solution
The method involves grouping syntax elements by type, such as pixel indices, escape pixels, run types, and run lengths, and signaling them in specific orders within the video bitstream to optimize parsing and reduce redundancy, including the use of last-run mode syntax elements to indicate copy-index or copy-above modes and omitting unnecessary signaling for identical palette indices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If palette indices and escape pixels are coded separately for each pixel position, then coding completeness is maintained, but syntax parsing throughput decreases and coding efficiency deteriorates
Solution Approach 1:
The patent merges separate coding of palette indices and escape pixels into a unified run-based coding structure. Instead of coding each pixel position independently, the invention combines multiple consecutive pixels with the same palette index into runs, and codes these runs collectively with shared syntax elements, thereby improving syntax parsing throughput while maintaining coding completeness
Solution Approach 2:
The patent segments the palette index map into runs of consecutive pixels with identical palette indices. By identifying and segmenting these runs, the invention enables efficient group coding where one set of syntax elements represents multiple pixels, reducing overall syntax complexity and improving parsing throughput
2Productivity
If all palette indices are signaled explicitly, then decoding accuracy is ensured, but bitstream redundancy increases and coding efficiency decreases
Solution Approach 1:
The patent extracts and removes redundant palette index information by identifying runs where consecutive pixels share the same palette index. Instead of signaling the same index repeatedly for each pixel, the invention extracts the unique index value once per run and applies it to all pixels in that run, eliminating bitstream redundancy while preserving decoding accuracy
Solution Approach 2:
The patent applies partial signaling by only coding palette indices that change between runs, rather than explicitly signaling every palette index for every pixel. This partial action approach maintains sufficient information for accurate decoding while significantly reducing bitstream redundancy
3Productivity
If run-based coding is implemented, then coding efficiency improves, but syntax element grouping complexity increases
Solution Approach 1:
The patent segments the pixel data into runs based on palette index equality, creating discrete coding units that can be efficiently processed. This segmentation transforms the raw pixel data into a structured sequence of runs, each characterized by a starting position, length, and palette index, simplifying the overall coding process despite the initial grouping complexity
Solution Approach 2:
The patent changes the coding parameters from per-pixel indexing to run-based parameters (start position, run length, palette index). This parameter transformation enables more efficient representation by capturing the essential information in fewer, more meaningful parameters that describe groups of pixels rather than individual pixels
Data Source
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AI summary
A method of palette index map coding of blocks in a picture by grouping coded symbols of the same type is disclosed for video encoder and decoder. In one embodiment, all syntax elements corresponding to the pixel index are grouped into a pixel index group, and all syntax elements corresponding to the escape pixel are grouped into an escape pixel group. All syntax elements corresponding to the run type and run length are grouped into an interleaved run type/run length group, or grouped into separate run type group and run length group. In another embodiment, the system parses from the video bitstream a last-run mode syntax element for a current block, where the last-run mode syntax element indicates whether a last run mode is a copy-index mode or a copy-above mode. Information associated with the last-run mode syntax element is used for reconstructing palette index map.