Color Volume Mapping for Wide Color Gamut Broadcast Signals
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Solution Overview
Problem
Current methods for transmitting and receiving digital broadcast signals struggle to accurately represent wide color gamut (WCG) content on legacy displays with narrow gamuts, leading to color distortion and loss of intended contrast and chroma details, as they do not adequately consider lightness information in gamut mapping.
Innovation Solution
A method involving three-dimensional color volume mapping, where lightness and hue information are separately mapped, and regions are divided to maintain balanced lightness and chroma information, preventing chroma inversion and color distortion by setting anchor points and using specific mapping functions for each region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If two-dimensional gamut mapping is performed without considering lightness information, then the mapping process is simple, but color distortion occurs and original colors cannot be represented accurately
Solution Approach 1:
The patent transitions from two-dimensional chroma mapping to three-dimensional color space mapping by incorporating lightness information. The mapping is performed in a three-dimensional space where lightness, chroma, and hue are simultaneously considered, enabling accurate color representation while maintaining manageable complexity through structured processing steps.
Solution Approach 2:
The patent divides the color space mapping into separate processing stages: first mapping lightness information, then mapping chroma and hue information based on the mapped lightness. This segmentation allows each dimension to be processed independently with appropriate algorithms, balancing simplicity and accuracy.
2Adaptability or versatility
If WCG content is mapped to narrow gamut displays using conventional methods, then the display compatibility is maintained, but chroma inversion and color distortion occur
Solution Approach 1:
The patent uses metadata about the original content's color space characteristics (BT.2020 gamut, HDR parameters) to guide the mapping process. This feedback mechanism allows the system to adjust mapping parameters dynamically, preventing chroma inversion and ensuring accurate color representation on narrow gamut displays while maintaining compatibility.
Solution Approach 2:
The patent transforms color information from the wide color gamut space (BT.2020) to the narrow color gamut space (BT.709) by changing multiple parameters simultaneously: lightness mapping, chroma scaling, and hue adjustment. These coordinated parameter changes prevent color distortion and maintain display compatibility.
3Power
If only chroma components are mapped excluding lightness components, then the mapping computation is reduced, but the lightness range limitation causes color representation failure
Solution Approach 1:
The patent segments the color mapping computation into distinct phases: lightness mapping first, then chroma-hue mapping conditioned on the mapped lightness. This segmentation improves computational efficiency by breaking down the complex 3D transformation into manageable steps while ensuring accurate color representation through proper sequencing.
Solution Approach 2:
The patent performs lightness mapping as a preliminary step before chroma and hue mapping. By establishing the mapped lightness values first, subsequent chroma and hue mappings can be performed with reference to these predetermined lightness levels, improving computational efficiency and ensuring color accuracy.
Data Source
AI summary
Disclosed is a color volume mapping method. A broadcast signal transmission method according to an embodiment of the present invention may comprise the steps of: encoding video data and metadata for the video data; generating a broadcast signal including the encoded video data and metadata; and transmitting the generated broadcast signal.