Color Palette Coding with Extended Tables for Bit Rate Reduction
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Solution Overview
Problem
Conventional color palette coding schemes are inefficient when dealing with high-quality coding and lossless coding conditions, particularly due to the high occurrence of escape colors in coding units, which leads to increased bit length and inefficiency in representing colors not covered by the limited major color table.
Innovation Solution
The proposed method involves using multiple color tables and a bit stream encoding scheme where a binary bit sequence represents up to 2N major colors and up to 2M extended colors, with each value uniquely indexing colors, and an escape color bit sequence is used only when necessary, allowing for variable length representation and efficient encoding of colors using Hoffman codes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a limited and fixed size major color table is used for palette coding, then the device complexity is reduced and ease of operation is improved, but the bit rate increases and coding efficiency deteriorates when QP is low or lossless coding is implemented due to frequent escape color occurrences
Solution Approach 1:
The patent divides the color representation into two segments: a major color table with limited fixed size for common colors, and an extended color table for additional colors. This segmentation allows the system to maintain the simplicity of a fixed-size table while adding capacity to reduce escape color occurrences, thereby reducing bit rate without sacrificing ease of operation.
Solution Approach 2:
The extended color table is nested within the palette coding structure as an补充 to the major color table. The encoding syntax includes a table identifier that nests the selection between major and extended tables, allowing the system to access a larger color space while maintaining the efficient fixed-size indexing mechanism of the major table.
2Productivity
If the major color table size is increased to cover more colors, then the occurrence of escape colors is reduced and coding efficiency is improved, but the device complexity increases and the fixed size limitation is violated
Solution Approach 1:
Instead of creating one large complex color table, the patent segments the color tables into a major table and an extended table. The major table maintains its fixed size for efficiency, while the extended table provides additional color coverage. This segmentation improves coding efficiency by reducing escape colors without increasing the complexity of the fixed-size major table structure.
Solution Approach 2:
The patent implements a partial extension of the color table by adding an extended color table that is activated only when needed. The encoding syntax selectively accesses either the major or extended table based on the color requirements, providing excessive color coverage capability without always incurring the full complexity overhead.
3Adaptability or versatility
If escape colors are frequently signaled with mode flag plus last index plus 24 bits color sample values, then all colors can be represented, but the bit length increases significantly and encoding efficiency deteriorates
Solution Approach 1:
The extended color table serves multiple functions: it acts as an extended palette for colors not in the major table, and it provides a more efficient encoding path than full escape color signaling. By universalizing the table-based indexing approach to include both major and extended tables, the system reduces bit length while maintaining the ability to represent all necessary colors.
Solution Approach 2:
Instead of signaling full 24-bit color values for escape colors, the patent copies the efficient indexing mechanism from the major color table and applies it to the extended color table. This allows escape-like colors to be represented with compact indices rather than full color samples, significantly reducing bit length while maintaining versatility.
Data Source
AI summary
The disclosure is directed to a method of color palette coding and an electronic device using the same method. The proposed method would include not limited to encoding, by using a processor, a bit stream to represent a color of a coding unit and storing the bit stream in a storage medium or transmitting the bit stream. The bit stream would include not limited to a binary bit representing a run flag, a N binary bit sequence representing up to 2N major colors in a coding unit with each of the possible values of the N binary bit sequence representing an unique major color index of N major color indices, and a M binary bit sequence representing up to 2M extended colors with each of the possible values of the M binary bit sequence representing an unique extended color index of M extended color indices.