Color Lookup Table Compression via YCbCr Segmentation
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Solution Overview
Problem
Three-dimensional lookup tables require significant memory capacity and bandwidth, making them inefficient for color transformations, especially when only certain color components change during the transformation process.
Innovation Solution
Converting to an intermediate color space that allows the use of two-dimensional lookup tables, reducing storage and memory bandwidth requirements, and adding extra color conversion steps to compensate for the lower dimensionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a three-dimensional lookup table is used for color transformation, then color accuracy is maintained, but memory capacity and memory bandwidth requirements become enormous
Solution Approach 1:
The patent segments the three-dimensional lookup table into multiple two-dimensional lookup tables by separating the luminance component (Y) from the chrominance components (Cb and Cr) in the YCbCr color space. This segmentation allows the large 3D table to be divided into smaller 2D tables that can be stored and processed more efficiently, reducing memory capacity requirements while maintaining color transformation accuracy.
Solution Approach 2:
The patent reduces the dimensionality of the lookup table from three dimensions (RGB) to two dimensions (YCbCr) by transforming the color space. This dimensionality change enables the use of smaller 2D lookup tables instead of large 3D tables, significantly reducing memory capacity and bandwidth requirements while preserving the necessary color transformation capabilities through the separation of luminance and chrominance information.
2Reliability
If a three-dimensional lookup table is used for color transformation, then complete color component transformation is achieved, but memory bandwidth requirements become enormous
Solution Approach 1:
The patent segments the color transformation process into separate operations on luminance (Y) and chrominance (Cb, Cr) components using two-dimensional lookup tables. This segmentation reduces memory bandwidth requirements because the smaller 2D tables require less data to be transferred from memory, while the color transformation remains complete through the coordinated processing of all components.
Solution Approach 2:
The patent extracts the luminance component (Y) from the chrominance components (Cb and Cr) in the YCbCr color space, allowing separate processing. By taking out the luminance information and processing it independently through 2D lookup tables, the patent reduces the amount of data that needs to be accessed from memory, thereby reducing memory bandwidth requirements while maintaining complete color transformation.
3Quantity of substance
If color space conversion to intermediate space is added, then lookup table size is reduced, but number of color conversion steps increases
Solution Approach 1:
The patent introduces an intermediate YCbCr color space to enable the use of two-dimensional lookup tables instead of three-dimensional ones. Although this adds a color space conversion step, the reduction in lookup table size from 48MB to a much smaller size makes the additional computational step worthwhile, as the overall system complexity is reduced through the use of smaller, more manageable data structures.
Data Source
AI summary
By converting a first color space to a second color space, using a two-dimensional lookup table in said second color space, and converting from said second color space to said first color space, it may be possible to use one or more two-dimensional lookup tables (LUTs) to do a task conventionally handled by three-dimensional lookup tables. This may reduce storage requirements and memory bandwidth requirements in some embodiments. In general a color pixel with N color components can be processed with n number of M dimensional LUT where M<N and n is some chosen positive integer number.