Color Mapping Function Offset Handling for Video Signals
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Solution Overview
Problem
Existing color mapping techniques for video signals, such as those described in WO 2015/007599 A1, US 7 692 666 B1, and US 2009/167955 A1, face limitations in handling offsets and dynamic range translation, particularly in YCbCr color difference encoding systems, where 1D LUTs cannot handle negative offsets and do not utilize the full dynamic range effectively.
Innovation Solution
A device and method for color mapping a video signal using a color mapping function that includes obtaining and applying specific offsets and a 3x3 matrix, along with one-dimensional mapping functions, to transform the video signal, ensuring accurate color space conversion and utilizing the full dynamic range by determining the color encoding systems and applying appropriate offsets before and after the matrix transformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If 1D LUTs are used for color mapping, then the implementation is simple, but they cannot handle negative offsets and do not utilize the full dynamic range
Solution Approach 1:
The patent combines multiple color mapping operations (matrix transformation and offset addition) into a unified color mapping function. This integration allows the system to handle both the rotational transformation and the offset translation (including negative offsets) within a single cohesive framework, resolving the limitation of 1D LUTs that could only handle simple look-up without negative offsets
Solution Approach 2:
The patent extends the color mapping approach from one-dimensional LUTs to a multi-dimensional transformation involving a 3x3 matrix and offset vectors. This dimensional expansion enables handling of the full color space transformation including negative offsets and full dynamic range utilization, while maintaining implementation efficiency through the structured mathematical framework
2Measurement precision
If the CRI color mapping function is used, then color space rotation is achieved, but it cannot handle offsets since 1D LUTs are defined with positive values only
Solution Approach 1:
The patent segments the color mapping process into distinct operations: a 3x3 matrix transformation for color space rotation and separate offset addition for translation. This segmentation allows each operation to be optimized independently, with the matrix handling rotation precision and the offset mechanism handling translation including negative values, thereby resolving the limitation of 1D LUTs
Solution Approach 2:
The patent introduces an intermediary offset mechanism that bridges the gap between the matrix transformation and the final color output. This intermediary layer handles the translation operation, including negative offsets, allowing the system to achieve both accurate color space rotation and proper offset handling that 1D LUTs alone could not provide
3Adaptability or versatility
If video signal standards use restricted dynamic range, then compatibility is maintained, but the full dynamic range is not utilized
Solution Approach 1:
The patent implements a dynamic offset mechanism that can adaptively adjust the color mapping based on the input signal characteristics. This dynamic approach allows the system to utilize the full dynamic range when available while maintaining compatibility with restricted range signals through appropriate offset selection, thereby resolving the trade-off between compatibility and full dynamic range utilization
Data Source
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AI summary
A method for color mapping a video signal comprising: • obtaining (8) at least one color mapping function; • determining (1000) the color encoding system of the video signal and of the mapped video signal; • determining (1010) said at least one offset responsive to said determined color encoding systems; and • applying (12) the color mapping function and the at least one offset on the video signal to obtain a mapped video signal.