SDR to HDR Conversion via Luminance Mapping Ratios
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Solution Overview
Problem
Converting between standard dynamic range (SDR) and high dynamic range (HDR) media formats is challenging due to non-linear relationships between luminance values, often resulting in noticeable chroma hue shifts, especially when converting between different HDR formats with varying bit depths or color spaces.
Innovation Solution
The proposed solution involves using luminance mapping ratios and direct R,G,B component mapping techniques to convert between SDR and HDR formats, employing linear or non-linear functions implemented in lookup tables or piecewise linear functions to adjust luminance and color components without causing hue shifts, allowing for bi-directional conversions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional SDR/HDR conversion methods are used, then format conversion is achieved, but chroma hue shift occurs that is noticeable to viewers
Solution Approach 1:
The patent applies parameter changes by using piecewise linear functions with different slopes for different luminance ranges, and by adjusting the chroma scaling factor based on luminance level. This allows the conversion process to adapt parameters dynamically, maintaining color accuracy across the full luminance range while enabling SDR/HDR format conversion.
Solution Approach 2:
The patent segments the luminance range into multiple intervals and applies different linear transformation parameters to each segment. By dividing the conversion process into discrete luminance ranges with tailored transformation functions, the system maintains chroma accuracy for both dark and bright regions while achieving format conversion.
2Illumination intensity
If luminance mapping is performed between SDR and HDR formats, then dynamic range is expanded, but non-linear relationships cause conversion difficulties
Solution Approach 1:
The patent segments the non-linear luminance mapping into multiple linear segments. By approximating the complex non-linear relationship with a series of linear pieces, the system achieves accurate luminance mapping across the full dynamic range while keeping the conversion process computationally manageable through simple linear operations in each segment.
Solution Approach 2:
The patent changes the transformation parameters based on the input luminance level. By selecting different linear transformation parameters for different luminance ranges, the system accurately maps between SDR and HDR luminance scales while maintaining a relatively simple piecewise linear computation process.
3Adaptability or versatility
If different HDR formats with varying bit depths are converted, then format flexibility is improved, but quantization contouring increases
Solution Approach 1:
The patent adjusts the luminance mapping parameters based on the target format's bit depth and characteristics. By optimizing the piecewise linear function parameters for each specific HDR format, the system achieves smooth luminance transitions and avoids quantization contouring while maintaining compatibility across different HDR formats with varying bit depths.
Data Source
AI summary
In some aspects, the disclosure is directed to methods and systems for transformation between media formats, such as between standard dynamic range (SDR) and high dynamic range (HDR) media or between HDR media formats, without undesired hue shifting, via one or both of a luminance mapping ratio technique and a direct color component mapping technique.