Illumination Compensation in Video Encoding Sub-Block Modes
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Solution Overview
Problem
The use of Local Illumination Compensation (LIC) in video compression technologies, such as those developed by the Joint Exploration Model (JEM), can be problematic in certain operating modes, leading to reduced compression efficiency due to limitations in determining LIC model parameters, and is often prohibited, which further impacts efficiency.
Innovation Solution
Enabling the use of LIC during potentially problematic situations by inferring the LIC flag and efficiently controlling LIC usage and parameter computation, particularly in sub-block temporal motion vector prediction and triangle partitions, to improve compression efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If LIC is used in sub-block based motion compensation or non-rectangular block partition modes, then compression efficiency is improved, but determination of LIC model parameters becomes problematic and may reduce efficiency
Solution Approach 1:
The patent applies local quality by making LIC parameter determination adaptive to different block types. For rectangular blocks, full LIC parameter determination is performed, while for sub-block based or non-rectangular blocks, the patent uses simplified or alternative approaches (such as inferring from neighboring blocks or using default parameters), thus optimizing compression efficiency without excessive complexity in each local context.
Solution Approach 2:
The patent introduces dynamic adaptation of LIC usage based on motion compensation mode. The system dynamically adjusts whether to apply LIC and how to determine its parameters depending on the specific block type and motion characteristics, allowing flexibility between compression efficiency and computational complexity based on local video content properties.
2Device complexity
If LIC is prohibited in certain operating modes to avoid parameter determination problems, then computational complexity is reduced, but compression efficiency deteriorates
Solution Approach 1:
The patent changes the parameters of LIC application based on operating mode. Instead of uniformly prohibiting LIC in certain modes, the patent modifies how LIC parameters are determined (e.g., using different derivation methods, inferring from neighbors, or adjusting parameter sets) to maintain compression efficiency while adapting to the constraints of sub-block based or non-rectangular motion compensation modes.
3Stability of the object's composition
If LIC is applied to all blocks uniformly, then illumination compensation consistency is improved, but processing overhead increases
Solution Approach 1:
The patent segments the video content into different block types (rectangular vs. sub-block based/non-rectangular) and applies LIC differently to each segment. This allows consistent illumination compensation where needed while avoiding unnecessary processing overhead in blocks where LIC is less effective or problematic, thus balancing consistency with processing efficiency.
Data Source
AI summary
A video codec can involve determining a motion compensation mode associated with encoding a first block of picture information, the motion compensation mode including a sub-block based motion compensation prediction mode or a non-rectangular block partition mode; determining that a second block of picture information spatially neighboring the first block was encoded or decoded based on an illumination compensation; and encoding or decoding the first block based on the motion compensation mode and the illumination compensation.