HDR Video Encoder Tone Mapping Metadata
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Solution Overview
Problem
Current HDR image encoding technologies struggle to effectively encode and render High Dynamic Range (HDR) images on various display devices with different peak brightness levels, as they often require significant bit increases or complex two-layer approaches, and lack a versatile solution for converting HDR images to suitable LDR images for diverse display ranges.
Innovation Solution
A more versatile HDR video encoding technology that includes an encoder and decoder system, which allows for the encoding of HDR images with a tone mapping function to map lower maximum luminance to a higher dynamic range, enabling the specification of color mapping functions for different display peak brightnesses, including 2000 nit, 5000 nit, and 100 nit displays, ensuring optimal rendering on a range of devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If LDR codec specifications are used to encode HDR images, then device complexity is reduced and compatibility is maintained, but encoding precision and visual quality are insufficient
Solution Approach 1:
The patent changes the luminance parameter representation by encoding HDR images with a reference white point of 2000 nit instead of the traditional 100 nit LDR standard. This parameter change allows the same codec infrastructure to handle HDR content by simply adjusting the reference luminance level, thereby improving encoding precision without significantly increasing device complexity
Solution Approach 2:
The patent creates a universal encoding approach that can handle both HDR and LDR content using the same codec specifications. By defining HDR encoding with a 2000 nit reference white and providing tone mapping functions, the system achieves multi-functionality where existing LDR codecs can be adapted to handle HDR content, maintaining compatibility while improving precision
2Illumination intensity
If HDR images are encoded with high maximum luminance (e.g., 5000 nit), then visual quality on high brightness displays is improved, but compatibility with standard displays (e.g., 100 nit) deteriorates
Solution Approach 1:
The patent applies preliminary tone mapping during the encoding process to prepare HDR content for different display capabilities. By pre-computing tone mapping functions that adapt the 2000 nit reference HDR content to various display peak brightness levels (including 100 nit LDR displays), the system ensures optimal visual quality across all display types without requiring real-time adaptation
Solution Approach 2:
The patent uses parameter changes in the tone mapping function to adapt the encoded HDR content to different display capabilities. By adjusting the output luminance parameter based on the target display's peak brightness, the system maintains visual quality and compatibility across the full range from 100 nit LDR to 5000 nit HDR displays
3Measurement precision
If bit depth is increased to encode HDR luminance details, then measurement precision is improved, but loss of time and processing overhead increase
Solution Approach 1:
The patent changes the luminance reference parameter to 2000 nit and uses this as the basis for encoding, which allows for efficient use of available bit depth. By establishing a well-defined reference white point and using standard tone mapping functions, the system achieves adequate luminance precision without requiring excessive bit depth increases, thus avoiding significant processing overhead
Data Source
AI summary
To enable future video transmission of a large range of HDR videos, and render them on displays of variable dynamic range or peak brightness capability, we describe an encoder (301) for encoding an input high dynamic range video set of images (Im_5000), having pixel colors with luminances lower than a first maximum luminance (L_max_M), into an encoded high dynamic range video (Im_2000), being a high dynamic range image, i.e. with a maximum luminance for displaying on a display with a corresponding peak brightness of at least 900 nit, being characterized in that the encoding definition allows encoding pixel color luminances up to a second maximum luminance (L_max_C), which is equal to or less than 50% of the first maximum luminance, the encoder comprising: a re-grading unit (320) arranged to allow a content creator to specify at least a tone mapping function (F_2Tu, 601) for color mapping the encoded high dynamic range video (Im_2000) of lower second maximum luminance (L_max_C) to a HDR video reconstruction (Im_5000*) of the high dynamic range video (Im_5000); and a formatter, arranged to write into a video signal (S_im) the encoded high dynamic range video (Im_2000) and as metadata the at least a tone mapping function (F_2Tu, 601), and related encoder and decoder embodiments and methods, and transmission technical components and technologies.