Luminance Signal Conversion Using EOTF Parameter Changes
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Solution Overview
Problem
Existing image signal processing apparatuses do not effectively handle luminance conversion between different luminance ranges, specifically from a first luminance range to a second range that is either larger or smaller.
Innovation Solution
A converting method that involves obtaining a first luminance signal, deciding a converted code value associated with the code value indicated by the first luminance signal for a second luminance range, and converting the first luminance signal into a second luminance signal indicating the converted code value, using both the first and second Electro-Optical Transfer Functions (EOTFs).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If luminance conversion between different luminance ranges is implemented, then the adaptability of the image signal processing apparatus is improved, but the device complexity increases
Solution Approach 1:
The patent applies parameter changes by utilizing different EOTF parameters (transfer functions) to represent different luminance ranges. The system switches between first EOTF and second EOTF based on the source and destination luminance ranges, enabling conversion between SDR and HDR without complex processing. This resolves the contradiction by using mathematical parameter transformation rather than hardware complexity.
Solution Approach 2:
The patent introduces EOTF (Electro-Optical Transfer Function) as an intermediary mechanism that mediates between different luminance ranges. The EOTF acts as a transfer function that maps luminance values from one range to another, simplifying the conversion process. This intermediary approach allows the system to handle luminance conversion systematically without direct complex processing.
2Adaptability or versatility
If luminance conversion is performed using traditional methods, then the luminance range can be changed, but image quality deteriorates
Solution Approach 1:
The patent maintains image quality by using EOTF parameter transformations that preserve the relationship between luminance values. Instead of direct linear conversion, the system uses the EOTF to map luminance values while maintaining the non-linear characteristics that define image quality. This ensures that tonal relationships and visual quality are preserved during conversion.
Solution Approach 2:
The patent replaces traditional mechanical or linear conversion methods with mathematical EOTF-based transformation. This substitution allows for more precise and quality-preserving conversion by using the appropriate transfer function that models the relationship between electrical signal and luminance, rather than simple linear scaling.
3Illumination intensity
If the luminance range is expanded, then the displayable luminance level is improved, but the processing complexity increases
Solution Approach 1:
The patent expands luminance range by switching to different EOTF parameters that support higher luminance values. When converting to HDR or expanding luminance range, the system uses the second EOTF which is designed for wider luminance ranges. This parameter-based approach allows luminance expansion without requiring complex processing algorithms, as the EOTF itself encodes the luminance mapping.
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AI summary
In a converting method relating to picture luminance according to one aspect of the present disclosure, the picture luminance is formed by luminance values in a first luminance range. In this method, a first luminance signal that indicates code values obtained by quantizing the luminance value of the picture is obtained, code values, which are associated with the code values indicated by the obtained first luminance signal by quantization for a second luminance range different in a maximum value from the first luminance range are determined as converted code values, and the first luminance signal is converted into a second luminance signal indicating the converted code values. As a result, the converting method is further improved.