Dual-LUT Color Conversion Logic for Memory-Accuracy Tradeoff
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Solution Overview
Problem
Existing color conversion systems face a trade-off between achieving high color accuracy, which requires large 3-D look-up tables (LUTs), and the need for cost and performance efficiencies, which are better served by smaller LUTs, as larger LUTs consume more memory and resources.
Innovation Solution
A system that includes both an on-chip primary color LUT and an off-chip secondary LUT, where the decision logic selectively accesses either based on the difference between neighboring pixels and a threshold, allowing interpolation when the secondary LUT does not have a direct match, to balance accuracy and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a large 3-D LUT is used to map all possible RGB combinations, then color accuracy is improved, but memory consumption and system cost increase
Solution Approach 1:
The patent divides the color conversion system into two segments: a small on-chip primary LUT for fast access and a larger off-chip secondary LUT for comprehensive color mapping. This segmentation allows the system to achieve high color accuracy using the secondary LUT while maintaining fast processing speeds through the primary LUT, avoiding the need to store a complete large LUT in on-chip memory.
Solution Approach 2:
The patent introduces a temporal dimension to the color conversion process by implementing a two-stage lookup approach. Instead of a single static LUT, the system performs sequential lookups across different memory hierarchies (on-chip then off-chip), effectively adding a time dimension to the color conversion operation to resolve the memory-speed-accuracy tradeoff.
2Measurement precision
If a large 3-D LUT is used, then color accuracy is improved, but access delays and processing time increase
Solution Approach 1:
The patent segments the LUT access process into two stages: first accessing a small on-chip primary LUT for immediate color values, then accessing the off-chip secondary LUT only when the primary LUT indicates a need for higher precision. This segmentation reduces average access time while maintaining color accuracy when needed.
Solution Approach 2:
The system performs preliminary color conversion using the on-chip primary LUT before determining whether additional lookup in the secondary LUT is necessary. This preliminary action allows most color conversions to complete quickly without accessing the larger off-chip memory, reducing overall access delays.
3Quantity of substance
If a small subset 3-D LUT is used, then memory usage is reduced, but color accuracy deteriorates due to unmapped RGB combinations
Solution Approach 1:
The patent segments the color mapping function across two LUTs: the primary LUT handles common RGB combinations with high precision, while the secondary LUT provides comprehensive coverage for all possible RGB combinations. This segmentation allows the system to achieve complete color mapping accuracy without requiring all data to reside in a single small memory.
Solution Approach 2:
The on-chip primary LUT acts as an intermediary between the input RGB values and the off-chip secondary LUT. It performs initial color conversion and determines whether further lookup is needed, mediating between the limited on-chip memory and the comprehensive off-chip memory to achieve both efficiency and accuracy.
Data Source
AI summary
A processor is provided that includes a primary memory and color conversion logic. The primary memory may store a first color look-up table (LUT) related to a second color space. The color conversion logic, in response to a received set of pixels having color values in a first color space, converts the received set of pixels to a second color space. The color conversion logic selectively accesses, based on a comparison of one or more pixel parameters to a threshold, one of the primary memory and a secondary memory located on a second device to obtain a color value of the second color space that is associated with each pixel of the set of pixels. The color conversion logic monitors the number of times that each of the primary memory and the secondary memory are accessed and automatically adjusts the threshold to maintain an access ratio.