Scene-Adaptive HDR Tone Mapping for Lower-Luminance Displays
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Solution Overview
Problem
Displaying mastered videos on displays with lower maximum luminance levels than the mastering monitor results in clipped luminance values, leading to reduced video quality and loss of image details.
Innovation Solution
Implementing HDR tone mapping methods with a parameterized tone map function using a normalized Bezier curve to adaptively adjust luminance values based on local contrast, allowing for efficient conversion from high to lower luminance levels while preserving image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a mastering monitor with high maximum luminance is used to produce mastered videos, then the luminance range and brightness levels of the original videos are optimized, but the videos display with clipped luminance values and reduced quality when shown on target displays with lower maximum luminance levels
Solution Approach 1:
The patent applies parameter changes by using a tone mapping function with adjustable parameters (alpha, beta, gamma) that can be optimized based on the specific luminance characteristics of both the mastering monitor and target display. This allows the tone mapping curve to be precisely tuned to preserve luminance relationships across different display capabilities, preventing clipping while maintaining image quality.
Solution Approach 2:
The invention implements dynamics by making the tone mapping process adaptive rather than static. The system dynamically adjusts the tone mapping parameters based on the actual luminance range and characteristics of the content being displayed, allowing optimal performance across varying video content and target display specifications.
2Adaptability or versatility
If standard tone mapping methods are used to convert videos from high luminance to lower luminance levels, then the videos can be displayed on target displays, but image details are lost and video quality is reduced
Solution Approach 1:
The patent applies local quality by implementing local contrast enhancement within the tone mapping function. Different regions of the luminance range are treated differently - highlights are preserved with one set of parameters while shadows and midtones use different parameter settings. This localized approach ensures that image details are maintained across the entire luminance spectrum rather than applying a uniform transformation that would lose information.
Solution Approach 2:
The invention uses feedback by incorporating metadata about the original mastered video's luminance characteristics into the tone mapping process. This metadata provides feedback about the source content's properties, allowing the tone mapping function to compensate for potential information loss by adjusting parameters based on the original luminance distribution and contrast relationships.
3Manufacturing precision
If re-mastering processes are performed to adapt videos for different luminance levels, then video quality can be maintained, but the time and cost associated with the process increase
Solution Approach 1:
The patent applies self-service by enabling the target display or playback system to perform the tone mapping operation automatically using the embedded metadata and parameterized function. This eliminates the need for manual re-mastering processes, as the system self-adjusts the luminance transformation based on the content's characteristics and the display's capabilities, significantly reducing time and cost while maintaining quality.
Solution Approach 2:
The invention implements preliminary action by pre-calculating and embedding the optimal tone mapping parameters and metadata into the video file during the mastering phase. This preliminary preparation allows for rapid, automated tone mapping at playback without requiring time-consuming re-mastering processes, as the heavy computational work has already been done and the parameters are ready for immediate application.
Data Source
AI summary
A method includes receiving a quantized video having a first maximum luminance level or brightness associated with a mastering display with which the quantized video was mastered. The method also includes de-quantizing the quantized video in order to generate a de-quantized video. The method further includes applying a scene-adaptive tone mapping function to the de-quantized video in order to generate a tone mapped video. In addition, the method includes displaying the tone mapped video on a target display. The tone mapped video has a second maximum luminance level or brightness associated with the target display, and the second maximum luminance level or brightness is less than the first maximum luminance level or brightness.