VVC ABT Split Restrictions for Lower Encoder Complexity
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Solution Overview
Problem
Existing video compression standards face challenges in optimizing the complexity and compression efficiency trade-off when incorporating Asymmetric Binary Tree (ABT) split modes, leading to increased encoder-side complexity and reduced coding efficiency.
Innovation Solution
Implement normative and non-normative restrictions on ABT partitioning, including limiting successive split modes, configuring supported transform sizes, and adapting LMCS chroma scaling parameters to optimize the trade-off between complexity and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If Asymmetric Binary Tree (ABT) split modes are introduced in VVC to improve compression efficiency, then coding efficiency is improved, but encoder-side complexity increases
Solution Approach 1:
The patent segments the encoding process by dividing ABT split mode evaluation into distinct phases: determining parent coding unit split modes, calculating sub-block indices, and applying restriction rules based on parent split mode and sub-block position. This segmentation allows the encoder to systematically manage complexity while maintaining compression efficiency gains from ABT.
Solution Approach 2:
The patent applies local quality by implementing position-dependent restriction rules where different sub-blocks (identified by index calculations) have different split mode allowances. Specifically, the restriction logic varies based on the parent split mode and the calculated sub-block index, creating localized encoding rules that reduce overall complexity while preserving efficiency in critical regions.
2Productivity
If unrestricted ABT split modes are used to maximize compression efficiency, then coding efficiency improves, but redundant split information increases
Solution Approach 1:
The patent extracts and removes redundant split information by applying restriction rules that prevent certain ABT split modes in specific contexts. The restriction logic identifies and eliminates unnecessary split mode evaluations based on parent split mode and sub-block index, thereby reducing redundant information in the bitstream while maintaining essential compression efficiency.
Solution Approach 2:
Instead of allowing all ABT split modes and then filtering redundancies, the patent inverts the approach by proactively restricting split modes based on parent configuration and sub-block position. This inversion prevents redundant split information from being generated in the first place, improving coding efficiency by reducing unnecessary data processing and transmission.
Data Source
AI summary
Some series of ABT split are normatively forbidden in order to limit the number of allowed series of splits, in a way that refines the trade-offs between the amount of allowed split series and the compression efficiency. In particular, a reduced combinatory in terms of allowed split series leads to reduced encoder-side complexity, in the rate distortion search for the best block partitioning. The normative split restrictions provide that when successively using horizontal or vertical then vertical or horizontal asymmetric splits, the considered succession of two splits leads to isolating the sub-area of the input block that is three-fourths the size of the parent block in width and height. Additional embodiments condition allowed splits on transform size, block size, and temporal layer of the slice and slice type.