HDR to SDR Video Signal Processing with Contrast Emphasis
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Solution Overview
Problem
When generating a Standard Dynamic Range (SDR) video signal from a High Dynamic Range (HDR) video signal captured by a camera, the contrast of high luminance portions is significantly reduced, leading to reduced visibility in the display video, and existing methods have not satisfactorily addressed this issue.
Innovation Solution
An imaging device is configured with a contrast emphasis signal generation unit and a VF signal processing unit that extract a high-pass luminance change component from the HDR video signal, generate a contrast emphasis signal, and add it to the SDR luminance reduction video signal to enhance the contrast of the high luminance portions, ensuring the SDR video signal maintains the visibility of high luminance details.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If knee correction is applied to generate SDR video from HDR video, then the luminance range is compressed to fit standard displays, but the contrast of high luminance portions is significantly reduced
Solution Approach 1:
The video signal processing is segmented into multiple stages: first applying knee correction to compress the overall luminance range for SDR compatibility, then separately processing the high luminance portion by extracting its contrast information and adding it back to the corrected signal. This segmentation allows different parts of the signal to be treated differently - the overall luminance is compressed while the local contrast in high luminance regions is preserved.
Solution Approach 2:
The invention applies local quality enhancement by specifically targeting the high luminance portions of the video signal. Instead of uniformly processing the entire signal, the system identifies and extracts contrast information from high luminance regions (using high-pass filtering) and selectively adds it back after knee correction. This ensures that contrast is preserved locally in regions where it matters most for visual quality.
2Adaptability or versatility
If knee correction is applied to compress HDR luminance to SDR range, then display compatibility is improved, but visibility of high luminance details is reduced
Solution Approach 1:
The invention introduces an intermediary processing step that extracts contrast information from the high luminance portions before the final SDR output. A high-pass filter acts as an intermediary to separate and extract the contrast component, which is then added back to the knee-corrected signal. This intermediary process prevents direct loss of detail information during the luminance compression.
Solution Approach 2:
The contrast information is extracted and preserved in advance (preliminarily) before the knee correction compresses the luminance range. By performing the high-pass filtering and contrast extraction before the final SDR conversion, the system ensures that detail information is captured and preserved, then reintroduced to the compressed signal to maintain visibility of high luminance details.
Data Source
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AI summary
An imaging device includes: an imaging unit having an imaging element; a first video signal processing unit that generates a first video signal of a first dynamic range from a pixel signal obtained by the imaging unit; and a second video signal processing unit that generates an information signal of a high-pass luminance change component of at least a high luminance portion from the first video signal, reduces a luminance value of a high luminance portion of the first video signal to generate a luminance reduction video signal of a second dynamic range narrower than the first dynamic range, and adds the generated luminance reduction video signal to the information signal of the luminance change component to generate a second video signal.