HDR Luminance Mapping for Ambient-Light Display Adaptation
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Solution Overview
Problem
Existing HDR video coding technologies struggle to optimally adapt image pixel luminances for display under varying ambient light conditions, particularly when transitioning between high dynamic range (HDR) and standard dynamic range (SDR) displays, without requiring excessive data communication or complex algorithms.
Innovation Solution
A method and apparatus for adapting HDR video pixel luminances using a luminance mapping function (F_L) to generate a desired look, allowing for efficient conversion between HDR and SDR formats, with metadata communication of the mapping function to enable display adaptation (FL_DA) for optimal viewing on different displays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If HDR video is encoded with absolute luminance values for optimal display on HDR displays, then image quality on HDR displays is improved, but image quality on SDR displays deteriorates due to improper luminance mapping
Solution Approach 1:
The patent implements dynamic metadata that changes over time to describe the relationship between HDR and SDR luminances. This allows the encoding system to adaptively adjust luminance mapping parameters based on the specific scene content and timing, enabling optimal display quality across both HDR and SDR displays without requiring static, one-size-fits-all mapping
Solution Approach 2:
The patent changes the luminance mapping parameters dynamically by introducing time-varying metadata that describes the relationship between HDR and SDR luminances. This allows the system to transform the absolute HDR encoding into relative SDR representation with proper adaptation, resolving the contradiction between maintaining absolute luminance accuracy for HDR displays and adapting to relative luminance requirements of SDR displays
2Measurement precision
If detailed luminance mapping metadata is communicated to enable precise display adaptation, then display adaptation accuracy is improved, but data communication overhead increases
Solution Approach 1:
The patent extracts only the essential luminance relationship information needed for display adaptation into compact metadata. Instead of communicating complete luminance mapping functions or extensive calibration data, the system extracts and transmits only the critical time-varying parameters that describe the HDR-to-SDR luminance relationship, achieving accurate adaptation with minimal data overhead
Solution Approach 2:
The patent performs preliminary calculation and preparation of luminance mapping parameters during the encoding phase. By pre-computing the necessary adaptation metadata and embedding it in the video stream, the system eliminates the need for complex real-time calculations at the display side, reducing both data transmission requirements and processing complexity while maintaining high adaptation accuracy
3Manufacturing precision
If complex algorithms are used to adapt HDR video for SDR displays, then adaptation quality is improved, but computational complexity increases
Solution Approach 1:
The patent introduces an intermediary metadata layer that mediates between HDR and SDR representations. This metadata acts as a bridge, providing the necessary transformation information without requiring complex direct mapping algorithms. The intermediary metadata simplifies the adaptation process by pre-encoding the relationship between HDR and SDR luminances, allowing displays to perform simple look-up operations rather than complex real-time calculations
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables efficient display adaptation of HDR video content to match varying ambient light conditions, ensuring optimal image quality on both HDR and SDR displays by minimizing data overhead and simplifying the display adaptation process.
Implementation Method 1
converting the difference (dif) to a luma difference (Ydif) by applying the opto-electronic transfer function (OETF_psy) with the difference as input to the opto-electronic transfer function (OETF_psy)
Data Source
AI summary
To obtain in a pragmatic manner better watchable images for various potentially considerably different viewing environment light levels, the inventor proposes a method of processing an input image to obtain an output image, comprising: obtaining for the pixels of the input image starting lumas (Yn_CC), by applying an opto-electronic transfer function (OETF_psy) to input luminances (L_in) of the input image; obtaining a minimum luminance of a targeted display (mL_VD), the targeted display corresponding to an end-user display (210), which end-user display is to be supplied with the output image to display it; obtaining a minimum luminance of the end-user display (mL_De) in a viewing room, wherein the minimum luminance of the end-user display (mL_De) is dependent on an amount of illumination in the viewing room; calculating a difference (dif) by subtracting the luminance of the end-user display (mL_De) from the minimum luminance of a targeted display (mL_VD); converting the difference (dif) to a luma difference (Ydif) by applying the opto-electronic transfer function (OETF_psy) with the difference as input to the opto-electronic transfer function (OETF_psy), which yields the luma difference as output; mapping the starting lumas by applying a linear function which applies as additive constant the luma difference multiplied by −1.0, and uses the luma difference increased by the value 1.0 as multiplier to multiply by the starting lumas, which yields mapped lumas (Yim); converting the mapped lumas (Yim) by applying the inverse of the opto-electronic transfer function to obtain normalized intermediate luminances (Lim); subtracting a second minimum luminance of an end-user display (mL_De2) divided by a maximum luminance of the output image (PL_O) from the intermediate luminances (Ln_im), and scaling the subtraction by 1.0 minus the result of dividing the second minimum luminance of an end-user display (mL_De2) by the maximum luminance of the output image (PL_O), to obtain final normalized luminances (Ln_f); multiplying the final normalized luminances (Ln_f) by the maximum luminance of the output image (PL_O), to obtain output luminances; and outputing the output luminances in a color representation of pixels of the output image.