HDR Image Encoding Dual Grading System
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Solution Overview
Problem
Current image and video encoding technologies, such as PAL and JPEG, are inadequate for handling high dynamic range (HDR) images, as they are primarily designed for low dynamic range (LDR) rendering and fail to effectively encode scenes with vast luminance variations, leading to loss of detail and inaccurate color representation.
Innovation Solution
A dual grading system that includes an automatic grading unit and a human grading unit, which generates two sets of mapping parameters to transform HDR images into a technically optimal second low dynamic range (LDR) image (GT_IDR) and an artistically preferred LDR image (Im_LDR), allowing for minimal information loss and accurate reconstruction of the HDR image.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current image and video encoding technologies (PAL, JPEG) are used for HDR images, then compatibility with legacy systems is maintained, but detail loss and inaccurate color representation occur due to inadequate handling of vast luminance variations
Solution Approach 1:
The patent divides the encoding process into two separate grading paths: technical grading (automatic) and artistic grading (manual). Each path processes the image differently to preserve different aspects of quality - technical grading preserves luminance accuracy for HDR reconstruction, while artistic grading optimizes for LDR display quality. This segmentation allows both HDR detail preservation and LDR compatibility without information loss.
Solution Approach 2:
The patent transforms the encoding approach by changing the luminance mapping parameters. Instead of using a single fixed gamma curve, it applies different luminance-correlate mapping functions for technical and artistic grading. The technical grading uses a mapping that preserves the full luminance range for accurate HDR reconstruction, while artistic grading applies a different mapping optimized for LDR display, thus preventing detail loss in both domains.
2Ease of operation
If a single LDR encoding is produced for legacy system compatibility, then ease of operation is improved, but the ability to reconstruct HDR images with optimal quality deteriorates
Solution Approach 1:
The patent segments the output into two distinct LDR images: GT_IDR (technically graded) and Im_LDR (artistically graded). The GT_IDR is specifically designed for HDR reconstruction with preserved luminance relationships, while Im_LDR is optimized for direct display on legacy systems. This segmentation allows legacy systems to operate easily with Im_LDR while HDR reconstruction quality is maintained through GT_IDR.
Solution Approach 2:
The patent introduces GT_IDR as an intermediary product that bridges between HDR source material and legacy LDR systems. This intermediate technically-graded image serves as a lossless intermediary that preserves all luminance information needed for HDR reconstruction, while still being viewable on legacy systems. It mediates between the conflicting requirements of HDR fidelity and LDR compatibility.
3Productivity
If automatic grading alone is used for LDR image generation, then productivity is improved, but artistic quality and color accuracy deteriorate
Solution Approach 1:
The patent segments the grading function into two independent processes: automatic technical grading for efficiency and manual artistic grading for quality. The automatic grading unit (203) handles the technical requirements of HDR preservation and luminance mapping, while the human grading unit (201) handles artistic quality and color accuracy. This segmentation allows both productivity and artistic quality to be optimized independently.
Solution Approach 2:
The patent uses the technically-graded image GT_IDR as an intermediary that the human grader can reference and adjust. This intermediary provides an objective technical baseline that preserves luminance accuracy, allowing the human grader to focus solely on artistic quality improvements without compromising technical fidelity. The GT_IDR serves as a mediator between automatic processing and manual refinement.
4Measurement precision
If HDR images are encoded with full luminance range preservation, then measurement precision is improved, but device complexity increases due to dual grading system requirements
Solution Approach 1:
The patent makes the encoding system multi-functional by producing two standardized LDR image formats (GT_IDR and Im_LDR) that can serve different purposes. GT_IDR serves both as a viewable image for legacy systems and as a reconstruction source for HDR, while Im_LDR serves as the primary display image. This universality allows the system to maintain measurement precision while reducing complexity by using standard LDR formats rather than requiring specialized HDR processing in all downstream systems.
Data Source
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AI summary
To allow graders to make optimally looking content of HDR scenes for various rendering displays, we invented an image encoder (202) comprising: an input (240) for a high dynamic range input image (M_HDR); an image grading unit (201) arranged to allow a human color grader to specify a color mapping from a representation (HDR_REP) of the high dynamic range input image defined according to a predefined accuracy, to a low dynamic range image (Im_LDR) by means of a human-determined color mapping algorithm, and arranged to output data specifying the color mapping (Fi(MP_DH)); and an automatic grading unit (203) arranged to derive a second low dynamic range image (GT_IDR) by applying an automatic color mapping algorithm to one of the high dynamic range input image (M_HDR) or the low dynamic range image (Im_LDR). We also describe and interesting new saturation processing strategy useful in the newly emerging high dynamic range image handling technology.