HDR Signal Reshaping and Coding Efficiency
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Solution Overview
Problem
Existing video compression standards, such as HEVC, are not optimized for coding high dynamic range (HDR) and wide color gamut (WCG) images, leading to inefficiencies in signal reshaping and coding.
Innovation Solution
The proposed solution involves a method for signal reshaping and coding of HDR images, where a decoder parses sequence processing set (SPS) data to detect HDR extension syntax structures, extracts post-processing information, and generates a second output signal based on this information to improve coding efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If existing video compression standards (HEVC) are used for HDR images, then compatibility with conventional displays is maintained, but coding efficiency deteriorates
Solution Approach 1:
The patent implements dynamic range conversion that adapts the HDR signal characteristics based on display capabilities. The system dynamically adjusts the transfer function (electro-optical transfer function or EOTF) applied to the decoded signal, switching between HDR-optimized transformations and SDR-compatible transformations based on the target display's dynamic range capabilities, thereby resolving the contradiction between maintaining compatibility and optimizing coding efficiency
Solution Approach 2:
The patent changes the parameter representation in the coded bitstream to include metadata about the transfer function and dynamic range characteristics. By encoding HDR images with explicit EOTF parameters and dynamic range information, the system enables both HDR and SDR displays to correctly interpret the signal, improving coding efficiency for HDR content while maintaining broad display compatibility through parameter-based adaptation
2Productivity
If signal reshaping is applied for HDR coding, then coding efficiency improves, but device complexity increases
Solution Approach 1:
The patent applies signal reshaping and transfer function conversion during the encoding stage rather than requiring complex processing at decoding. By pre-transforming the HDR signal using appropriate EOTFs and embedding the transformation parameters in the bitstream, the system achieves improved coding efficiency while keeping the decoder relatively simple, as the heavy lifting is performed during encoding
Solution Approach 2:
The patent introduces metadata about the transfer function and dynamic range characteristics as an intermediary between the encoded signal and the display device. This intermediary information allows displays to correctly interpret and render HDR content without requiring complex embedded processing, thereby improving coding efficiency while managing device complexity through information-based mediation rather than hardware complexity
Data Source
AI summary
In a method to improve the coding efficiency of high-dynamic range (HDR) images, a decoder parses sequence processing set (SPS) data from an input coded bitstream to detect that an HDR extension syntax structure is present in the parsed SPS data. It extracts from the HDR extension syntax structure post-processing information that includes one or more of a color space enabled flag, a color enhancement enabled flag, an adaptive reshaping enabled flag, a dynamic range conversion flag, a color correction enabled flag, or an SDR viewable flag. It decodes the input bitstream to generate a preliminary output decoded signal, and generates a second output signal based on the preliminary output signal and the post-processing information.