SDR to HDR Video Signal Conversion via Luminance Expansion
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Solution Overview
Problem
Conventional methods for converting standard dynamic range (SDR) video to high dynamic range (HDR) video are time-consuming, require skilled operators, and are not suitable for live broadcasts, as they involve manual colour grading processes.
Innovation Solution
A method that expands the luminance component of SDR video signals in a linear manner above a threshold, allowing the signals to be usable on HDR devices without affecting other parts of the signal range, implemented through a converter that uses a 3D look-up table or similar processing steps, ensuring the conversion is content-independent and reversible.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If manual colour grading is used to convert SDR video to HDR video, then the quality of the converted video is improved, but the processing time and cost increase significantly
Solution Approach 1:
The patent creates a mathematical model that copies the effect of manual colour grading through automated algorithms. By analyzing the relationship between SDR and HDR video signals, the invention reproduces the quality improvements of manual grading without requiring skilled operators, thus resolving the contradiction between quality and processing time
Solution Approach 2:
The invention transforms the video signal by applying parameter changes to the luminance component. By modifying the transfer function and adjusting luminance parameters according to the established model, the system automatically achieves HDR conversion with quality comparable to manual grading but without the time and cost overhead
2Manufacturing precision
If manual colour grading is used for SDR to HDR conversion, then the video quality is improved, but the process cannot be applied to live broadcasts
Solution Approach 1:
The patent replaces the mechanical/manual colour grading process with an automated electronic system. By substituting human operators with a computational model that processes video signals in real-time, the invention enables HDR conversion for live broadcasts while maintaining quality improvements, thus resolving the contradiction between quality and real-time capability
3Manufacturing precision
If the luminance component is expanded to utilize HDR dynamic range, then the perceived quality on HDR displays is improved, but other parts of the signal range may be affected
Solution Approach 1:
The patent applies local quality by selectively expanding only the highlight portions of the luminance signal above a specific threshold. By targeting only the relevant portion of the signal range for expansion while leaving other portions unchanged, the invention improves perceived quality on HDR displays without adversely affecting other parts of the signal, thus resolving the contradiction between quality improvement and signal integrity
Data Source
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AI summary
A method and device for converting a video signal from a lower dynamic range source to produce a signal usable by target devices of a higher dynamic range comprises converting with a convertor that implements a process in which a received signal is received as a luminance component and separate colour components, A modified luminance component is then produced by applying an expansion function to the luminance component for luminance values above a threshold, applying a gamma function and then applying a scaling function. The modified luminance and separate colour components are then provided as an output signal for display on a target device of a higher dynamic range. The expansion of luminance ensures that the luminance range appropriately matches the range for a target display. By applying the expansion luminance values above a threshold, values below a threshold can be maintained with appropriate values for display.