Color Gamut Mapping Mode Selection for HDR Content
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Solution Overview
Problem
Low-cost Consumer Electronics (CE) devices struggle with processing explicit color gamut mapping parameters, leading to degraded user experience in premium HDR content delivery, as they either discard or use 'blind' gamut mapping, which compromises the quality of HDR rendering.
Innovation Solution
A method for generating a second image from a first image using a color gamut mapping process controlled by a bitstream, which selects a substitute gamut mapping mode from additional data when explicit parameters are not enabled, ensuring high-fidelity color rendering by choosing between preset modes and explicit parameters, and determining a substitute mode based on the color spaces of the images and displays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If explicit color gamut mapping parameters are used, then color rendering fidelity is improved, but device complexity increases making low-cost devices unable to process them
Solution Approach 1:
The patent introduces a fallback mechanism that uses simple preset gamut mapping modes (BT.709_to_P3D65, BT.709_to_BT.2020) for low-cost devices that cannot process explicit parameters. These preset modes act as simplified, pre-computed solutions that maintain acceptable quality without requiring complex processing capabilities, effectively providing a 'cheap' alternative for devices with limited resources.
Solution Approach 2:
The patent changes the parameter representation from complex explicit gamut mapping parameters to simple preset mode indicators (0, 1, or 2). This parameter transformation allows low-cost devices to process the information easily while still achieving color gamut mapping, resolving the contradiction between fidelity and device complexity by simplifying the parameter structure.
2Adaptability or versatility
If preset gamut mapping modes are used, then device compatibility is improved, but color rendering fidelity deteriorates compared to explicit parameters
Solution Approach 1:
The patent implements a dynamic parameter selection mechanism where the system adapts the gamut mapping approach based on device capabilities. HDR-capable devices receive and process explicit parameters for high fidelity, while SDR devices automatically receive preset mode indicators for compatibility. This dynamic adaptation resolves the contradiction by allowing each device type to operate at its optimal capability level.
Solution Approach 2:
The patent segments the gamut mapping parameter set into two distinct parts: a compact preset mode indicator (0, 1, or 2) for SDR devices, and detailed explicit parameters for HDR devices. This segmentation allows each device type to process only the relevant portion, maintaining both broad compatibility and high fidelity where needed.
3Adaptability or versatility
If dual-layer coding is used to support SDR backward compatibility, then compatibility is improved, but system complexity increases and not all distribution workflows are adapted
Solution Approach 1:
The patent merges SDR and HDR compatibility into a single-layer distribution system. By embedding both preset mode indicators and explicit parameters in one bitstream, the system eliminates the need for separate SDR and HDR layers, reducing distribution complexity while maintaining backward compatibility with SDR devices and native support for HDR devices.
Solution Approach 2:
The patent creates a universal gamut mapping parameter structure that serves both SDR and HDR devices simultaneously. The preset mode indicator field can be interpreted by SDR devices for basic compatibility, while HDR devices can utilize the full explicit parameter set, making the same bitstream structure universally applicable across different device capabilities without requiring separate encoding passes.
Data Source
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AI summary
Applying a color gamut mapping process on a first image to generate a second image, where the content of the first and second images is similar but the respective color spaces of the first and second images are different, can involve controlling the color gamut mapping process at least by a color gamut mapping mode obtained from a bitstream where the color gamut mapping mode belongs to a set comprising at least two preset modes and an explicit parameters mode and, if the obtained color gamut mapping mode is the explicit parameters mode and the color gamut mapping process is not enabled for the explicit parameters mode, controlling the color gamut mapping process by a substitute color gamut mapping mode determined from additional data.