3D LUT Encoding for Compatible Wide-Color Video Rendering
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Solution Overview
Problem
Existing rendering devices struggle with adapting to diverse color spaces and display characteristics, particularly with the introduction of new color formats like ITU-R Recommendation BT.2020, leading to issues in color conversion and compatibility with legacy devices.
Innovation Solution
A method and system for encoding and decoding color transforms using Supplemental Enhancement Information (SEI) messages, which include first parameters describing video signal characteristics and second parameters representing the color transform, allowing for flexible and compatible color mapping across different display environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a new wider color space format (Rec. 2020) is introduced to improve color rendering quality, then color gamut and rendering accuracy are improved, but compatibility with legacy devices is worsened
Solution Approach 1:
The patent introduces color metadata as an intermediary element that carries color transform information between the video stream and rendering devices. This metadata acts as a bridge, enabling legacy devices to interpret and render Rec. 2020 content by providing them with the necessary color space transformation parameters without requiring the devices themselves to natively support the new color format.
Solution Approach 2:
The patent encodes color transform parameters (such as 3D LUT data, matrix coefficients, and transfer characteristics) as modifiable parameters in the video bitstream. Rendering devices can dynamically adjust their color rendering behavior by applying these parameters, allowing the same video content to be optimally displayed across different device capabilities while maintaining color accuracy.
2Loss of information
If color transform parameters are transmitted in private streams at the transport system level, then color metadata can be delivered to rendering devices, but most transmission systems discard these metadata because they do not know how to interpret them
Solution Approach 1:
The patent designs the color metadata structure to be universally compatible with existing video coding standards (HEVC, SHVC). The metadata is embedded using standard SEI message mechanisms that are already recognized by transmission systems, allowing the same infrastructure to carry both video data and color transformation information without requiring separate interpretation protocols.
Solution Approach 2:
The rendering devices are equipped with the capability to self-interpret and apply the color metadata without requiring external processing or conversion. The metadata contains self-descriptive information including transform type identifiers and parameter values that devices can automatically process based on their supported feature sets.
3Measurement precision
If deterministic color space conversion is used to ensure accurate color transformation, then color accuracy is improved, but non-deterministic operations such as color grading cannot be supported
Solution Approach 1:
The patent enables dynamic color transformation by allowing the selection of different color transform types (deterministic matrix operations or non-deterministic 3D LUT-based transformations) based on the content characteristics and target application. The encoded metadata indicates the transform type, allowing rendering devices to apply the appropriate method - deterministic transforms for standard content and more flexible non-deterministic transforms for color-graded content requiring artistic adjustment.
Data Source
AI summary
In an example method, for a plurality of octants, residual information is obtained for one or more vertices of the respective octant, where the vertices correspond to respective points in a three-dimensional lookup table. The lookup table is decoded recursively as follows: at least a first one of the plurality of octants is decoded by reconstructing at least a first color sample value from the residual information for at least a first vertex of the first octant; and a plurality of second octants in the plurality of octants are decoded, where the second octants are obtained by splitting the first octant. A color transform is then applied based on the decoded lookup table.