Tone Mapping Switching for HDR Video Stability
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Solution Overview
Problem
Dynamic metadata-based tone mapping in video display systems can lead to unstable video quality, particularly when graphics such as subtitles or menus are overlaid on HDR videos, causing luminance and color variations that are undesirable.
Innovation Solution
The video reproduction apparatus transmits a 'graphics overlay flag' to the video display apparatus, allowing it to switch between dynamic and fixed tone mapping or adjust tone mapping intensity based on the presence and state of graphics, ensuring consistent luminance and reducing discontinuities in tone mapping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dynamic metadata-based tone mapping is used to enhance HDR video quality, then video luminance and color accuracy are improved, but video stability deteriorates when graphics are overlaid
Solution Approach 1:
The system dynamically switches between dynamic tone mapping and fixed tone mapping modes based on the presence of overlaid graphics. When graphics are detected, the system transitions from dynamic metadata-based tone mapping to fixed tone mapping, thereby maintaining video stability while preserving the ability to achieve high luminance and color accuracy when graphics are not present
Solution Approach 2:
The invention changes the tone mapping parameters from dynamic (time-varying metadata) to fixed (constant values) depending on the graphical overlay state. This parameter switching resolves the contradiction by adapting the tone mapping behavior to the specific display conditions, ensuring both accuracy and stability are maintained in their respective contexts
2Manufacturing precision
If dynamic tone mapping is applied to HDR videos, then video quality is enhanced, but luminance consistency of overlaid graphics deteriorates
Solution Approach 1:
The invention extracts the tone mapping operation from the main video processing chain when graphics are overlaid, applying fixed tone mapping separately to maintain consistent luminance for graphical elements. This separation allows the main video to benefit from enhanced quality processing while graphics maintain their luminance consistency independently
3Measurement precision
If dynamic metadata is used for tone mapping, then HDR video fidelity is improved, but transition smoothness between tone mapping states deteriorates
Solution Approach 1:
The system performs preliminary detection of graphic overlay states and proactively switches to fixed tone mapping mode before luminance inconsistencies can occur. This preliminary action prevents the need for corrective transitions, ensuring smooth visual experience while maintaining HDR video fidelity through appropriate tone mapping mode selection
Data Source
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Figure 3A~3B
AI summary
A video display system (100) includes: a tone mapping processor (123B) that performs a tone mapping process of converting a luminance of a video by using conversion characteristics according to a maximum luminance of the video; and a display (124) that displays the video that has undergone the tone mapping process. The tone mapping processor (123B) switches between a first tone mapping process of dynamically changing the conversion characteristics according to a time-depend change in the maximum luminance of the video and a second tone mapping process that is performed using constant conversion characteristics irrespective of the time-depend change in the maximum luminance of the video. When the tone mapping process used is switched from the second tone mapping process to the first tone mapping process, the conversion characteristics used is changed gradually or stepwise from the constant conversion characteristics to dynamically changing conversion characteristics over a plurality of frames.