SL-HDR1 SDR Chroma Correction to Prevent HDR Clipping
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Solution Overview
Problem
In SDR/HDR distribution systems, discrepancies in precision levels across different modules lead to display errors due to clipping of values during calculations, particularly when entities perform internal calculations using varying bit-depth and range values, causing unacceptable errors in displayed HDR video.
Innovation Solution
A method and device that utilize a color correction function to obtain chroma components, estimate a clipping factor, and apply correction factors based on ratios dependent on sample characteristics like brightness and saturation to prevent clipping, ensuring accurate conversion from SDR to HDR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If different entities perform internal calculations using varying bit-depth and range values, then each entity can optimize for its specific processing requirements, but display errors occur due to clipping of values during calculations
Solution Approach 1:
The patent applies preliminary action by estimating the clipping factor before actual HDR conversion operations. The method calculates a clipping factor based on SDR picture characteristics (luma and chroma components) and uses this pre-computed factor to adjust the conversion process, preventing clipping errors before they occur during the actual HDR rendering stage.
Solution Approach 2:
The patent implements feedback by using the estimated clipping factor to correct the SDR picture before HDR conversion. The clipping factor serves as a feedback signal that indicates potential clipping issues, and the method adjusts the conversion parameters accordingly to maintain display accuracy while allowing different entities to use their preferred calculation precision levels.
2Measurement precision
If calculations are performed with high precision, then display errors are reduced, but computational complexity and processing time increase
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the clipping factor based on the characteristics of the SDR picture being processed. Instead of using a fixed high-precision conversion approach, the method modifies the conversion parameters (clipping factor, scaling factors) according to the specific image content, achieving sufficient precision without unnecessary computational complexity.
Solution Approach 2:
The patent applies partial action by performing precision adjustments only where necessary. The method calculates clipping factors selectively based on chroma component thresholds and applies corrections only when clipping is detected or predicted, rather than applying high-precision processing to all image data uniformly, thus reducing overall computational complexity.
3Reliability
If clipping prevention is implemented through correction factors, then display errors are limited, but additional calculation steps are required
Solution Approach 1:
The patent applies preliminary action by pre-calculating the clipping factor based on SDR picture characteristics before the main HDR conversion process. This allows the correction to be prepared in advance and applied efficiently during rendering, minimizing the impact on processing speed while ensuring display accuracy.
Solution Approach 2:
The patent replaces complex multi-step clipping prevention mechanisms with a simplified approach using a single clipping factor parameter. Instead of implementing multiple correction algorithms or complex validation processes, the method uses this one parameter to control and prevent clipping, significantly reducing computational overhead while maintaining effectiveness.
Data Source
AI summary
A method for correcting a SDR video in a SL-HDR1 system comprising identifying samples of a SDR picture the chroma components values of which risking to be clipped during a SL-HDR1 process; and, correcting the identified samples to prevent from the clipping before a generation of a HDR picture from the SDR picture.