HDR to SDR Invertible Mapping for Backward Compatible Video Distribution
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Solution Overview
Problem
Current methods for distributing compressed High-Dynamic-Range (HDR) pictures/video face challenges in minimizing bitrate while ensuring good quality for both HDR and Standard-Dynamic-Range (SDR) versions, maintaining backward compatibility, and efficiently using legacy infrastructure.
Innovation Solution
A method involving invertible mapping from HDR to SDR and vice versa, using a three-step process including luminance dynamic reduction, chrominance component determination, and gamut correction, along with nonlinear dynamic expansion and reduction functions, to encode and decode HDR content compatible with legacy SDR workflows.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If HDR content is distributed using legacy SDR infrastructure, then backward compatibility is maintained and existing infrastructure can be used, but coding errors increase and visual quality deteriorates
Solution Approach 1:
The patent introduces an intermediate SDR representation as a mediator between HDR content and legacy SDR infrastructure. The invertible mapping process creates an SDR version that can be distributed through existing infrastructure while maintaining the ability to perfectly reconstruct the original HDR content, thus serving as a bridge that preserves both compatibility and quality.
Solution Approach 2:
The patent transforms HDR parameters (high dynamic range luminance values) into SDR parameters (standard dynamic range luminance values) through invertible mapping functions. This parameter transformation allows HDR content to be compatible with SDR infrastructure while preserving the ability to recover original HDR parameters without quality loss.
2Manufacturing precision
If separate distribution channels are used for HDR and SDR content, then quality for both formats is maintained, but bandwidth consumption increases
Solution Approach 1:
The patent merges HDR and SDR distribution into a single channel by encoding both the SDR representation and the invertible mapping parameters in one bitstream. This allows receivers to obtain both SDR and HDR content through one distribution channel, eliminating the need for separate channels while maintaining quality for both formats.
Solution Approach 2:
The patent creates a universal distribution format that serves multiple functions: it provides SDR content for legacy devices, HDR content for advanced devices, and the mapping information needed for conversion. This multi-functional approach eliminates redundant transmission and optimizes bandwidth usage.
3Device complexity
If simple luminance reduction is used to convert HDR to SDR, then processing complexity is reduced, but color accuracy and visual quality deteriorate
Solution Approach 1:
The patent performs preliminary chroma scaling during the HDR-to-SDR conversion process. By pre-adjusting the chrominance components based on the luminance mapping, the system ensures that color accuracy is preserved in the SDR representation. This preliminary action prevents color distortion that would otherwise occur with simple luminance reduction.
Solution Approach 2:
The patent applies coordinated changes to multiple parameters during conversion: luminance values are mapped from HDR to SDR range, and chrominance values are scaled accordingly. This coordinated parameter transformation maintains color relationships and visual quality while managing processing complexity through established mapping functions.
Data Source
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AI summary
A decoding method is disclosed that comprises: - decoding at least one luma component and two chroma components from a bitstream; - decoding color metadata, said metadata comprising at least one of: a syntax element representative of a color conversion type, a syntax element representative of an inverse transfer type and a syntax element representative of a color conversion matrix; - color converting the luma and/or chroma components responsive to said syntax element representative of a color conversion type; - applying an inverse transfer operation on the color converted luma and/or chroma to obtain a first, a second and a third component responsive to syntax element representative of an inverse transfer type; and - applying a color conversion matrix responsive to said syntax element representative of a color conversion matrix to obtain and RGB high dynamic range picture.