Color Remapping SEI Message Adaptation for Video Chroma Formats
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Solution Overview
Problem
The existing color remapping information (CRI) Supplemental Enhancement Information (SEI) message in video coding standards, such as HEVC, is limited in its applicability and flexibility, particularly restricting color remapping processes to only 4:4:4 decoded samples, and does not effectively support monochrome video content or other chroma formats like 4:2:0 and 4:2:2 domains.
Innovation Solution
The proposed solution involves modifying the semantics of the CRI SEI message to allow its application across various video content types, including 4:2:0, 4:2:2, and 4:0:0 domains, by restricting certain syntax elements based on chroma formats and color remap values, enabling the use of pre-lookup tables and color remap matrices only when necessary, and allowing for identity mappings in cases where all color components are not present.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the CRI SEI message is restricted to only 4:4:4 decoded samples, then the color remapping process is simpler to implement, but the applicability to various video content types (4:2:0, 4:2:2, monochrome) is limited
Solution Approach 1:
The patent applies different color remapping processes to different chroma formats based on their specific characteristics. For 4:4:4 samples, the full color remapping process is applied. For 4:2:0 and 4:2:2 samples, the process is adapted to work directly on subsampled chroma components. For monochrome content, only luma remapping is performed. This localized adaptation resolves the contradiction by making the system versatile across content types while maintaining appropriate complexity for each case.
Solution Approach 2:
The patent creates a universal color remapping framework that can handle multiple chroma formats (4:4:4, 4:2:2, 4:2:0) and content types (color and monochrome) through a single unified SEI message structure. The color remapping model is designed to be format-agnostic, automatically adapting its operation based on the input chroma format, thereby achieving universality without requiring separate processing paths for each format.
2Manufacturing precision
If upsampling is performed to convert 4:2:0 or 4:2:2 samples to 4:4:4 before color remapping, then the color remapping model can be applied as defined, but the computational overhead increases and video quality may be degraded
Solution Approach 1:
Instead of upsampling chroma components to 4:4:4 before applying color remapping (the conventional approach), the patent inverts the approach by applying color remapping directly to the subsampled 4:2:0 or 4:2:2 chroma components. This reversal eliminates the need for computationally intensive upsampling operations while maintaining color remapping accuracy, as the remapping is applied to the actual chroma data available rather than to upsampled interpolations.
3Adaptability or versatility
If the CRI SEI message syntax elements are made flexible to support all chroma formats, then the message becomes more versatile, but the message structure becomes more complex
Solution Approach 1:
The patent introduces dynamic syntax elements in the CRI SEI message that adapt their presence and interpretation based on the chroma format of the video content. The color_remap_id syntax element dynamically indicates which color components should be remapped, allowing the message structure to flexibly accommodate different chroma formats without requiring separate message types. This dynamic approach provides versatility while maintaining a relatively simple unified message structure.
Data Source
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AI summary
Systems, methods, and computer readable media are described for providing improved color remapping. In some examples, a video bitstream is obtained that includes a plurality of pictures having a first color characteristic. A color remapping information (CRI) supplemental enhancement information (SEI) message is identified from the video bitstream. A restriction is placed on the CRI SEI message such that a value of a syntax element of the CRI SEI message is restricted based on a condition. One or more samples of the plurality of pictures is remapped from the first color characteristic to a second color characteristic using a color remapping model of the CRI SEI message according to the restriction. In some cases, the condition is a chroma format of the plurality of pictures, in which case the value of the syntax element of the CRI SEI message is restricted based on the chroma format. In some cases, the condition is a color remap value identifying a purpose of the color remapping model of the CRI SEI message, in which case the value of the syntax element of the CRI SEI message is restricted based on the color remap value.