Adaptive Color Transform Unit Size Restriction
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Solution Overview
Problem
Current video coding technologies face challenges in efficiently managing transform sizes during adaptive color transform, leading to increased buffer requirements and reduced coding efficiency, especially when the adaptive color transform is enabled or disabled at the coding unit level.
Innovation Solution
The implementation of specific maximum transform sizes based on the adaptive color transform (ACT) flag, allowing for vertical or horizontal splits of transform units, depending on the ACT flag status and block dimensions, to optimize transform unit processing and reduce buffer requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If adaptive color transform is enabled at coding unit level, then coding efficiency is improved, but buffer requirements increase
Solution Approach 1:
The transform unit is divided into multiple sub-transform units through vertical or horizontal binary splits when the transform block size exceeds the maximum transform size. This segmentation allows processing of large blocks in smaller manageable units, reducing the buffer memory required for transform operations while maintaining the coding efficiency benefits of adaptive color transform.
Solution Approach 2:
The maximum transform size is dynamically adjusted based on the adaptive color transform flag status. When ACT is enabled, a smaller maximum transform size (e.g., 32×32) is used compared to when ACT is disabled (e.g., 64×64). This dynamic adjustment optimizes the balance between coding efficiency and buffer requirements adaptively.
2Productivity
If transform unit size is increased, then processing efficiency is improved, but buffer requirements increase
Solution Approach 1:
Large transform blocks are recursively divided into smaller sub-transform units through binary splitting (vertical or horizontal) when they exceed the maximum transform size. This segmentation enables processing of large blocks in smaller units that require less temporary buffer memory, while still achieving the processing efficiency of handling large blocks through systematic decomposition.
Solution Approach 2:
Different maximum transform sizes are applied locally based on the adaptive color transform flag status and block characteristics. Instead of using a uniform maximum transform size throughout, the system adapts the transform size to local requirements, using smaller sizes where ACT is enabled and larger sizes where it is disabled, optimizing both processing efficiency and buffer usage.
3Adaptability or versatility
If coding unit level ACT flag is used, then adaptability is improved, but device complexity increases
Solution Approach 1:
The maximum transform size is dynamically determined based on the ACT flag status at the coding unit level. When ACT is enabled, a smaller maximum transform size is used; when disabled, a larger size is used. This dynamic adaptation provides versatility in handling different block types while maintaining relatively simple decision logic based on a single flag.
Solution Approach 2:
The system changes the parameter of maximum transform size based on the ACT flag state. By modifying this key parameter adaptively, the system achieves high adaptability to different block characteristics and ACT requirements without introducing complex control mechanisms, as the parameter change is driven by a simple flag condition.
Data Source
AI summary
Aspects of the disclosure provide methods, apparatuses, and non-transitory computer-readable storage mediums for video encoding/decoding. An apparatus includes processing circuitry that decodes prediction information for a current block in a current picture that is a part of a coded video sequence. The prediction information includes an adaptive color transform (ACT) flag indicating whether ACT is enabled for the current block. The processing circuitry determines whether a transform unit (TU) split is performed on the current block based on a maximum transform size that is determined according to whether the ACT flag indicates the ACT is enabled for the current block. The processing circuitry determines a type of the TU split in response to the TU split being determined to be performed on the current block. The processing circuitry performs the TU split on the current block based on the determined type of the TU split.