Multiple Transform Selection for Video Coding Efficiency
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Solution Overview
Problem
Existing video coding standards face challenges in efficiently managing multiple transforms, leading to increased computational complexity and reduced coding efficiency, especially with the growing demand for higher resolution videos.
Innovation Solution
The proposed method involves selecting a common transform as both a vertical and horizontal transform within a multiple transform selection (MTS) process, and applying these transforms to video blocks during the conversion between the current block and its bitstream representation, while also considering sub-block transforms and transform coefficient zero-out processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple transforms are applied to video blocks in existing video coding standards, then coding efficiency is improved, but computational complexity increases
Solution Approach 1:
The transform process is segmented into multiple stages: primary transform applied to the residual block, followed by secondary transform applied to selected coefficient blocks. This segmentation allows the system to apply complex transforms only where needed rather than uniformly across all blocks, improving coding efficiency while managing computational complexity through selective application.
Solution Approach 2:
The patent applies transforms partially by using transform skip flags to conditionally apply or skip the secondary transform based on block characteristics. Additionally, the system applies transforms excessively in certain regions by using different transform types (DST-VII, DCT-VIII) for different coefficient blocks, allowing the encoder to achieve better compression by applying transforms where they provide the most benefit while avoiding them where unnecessary.
2Productivity
If multiple transform types are selected for different video blocks, then coding efficiency is improved, but device complexity increases
Solution Approach 1:
The transform selection is made dynamic through the use of transform skip flags and block-type-dependent transform selection. The encoder dynamically chooses between different transform types (DST-VII, DCT-VIII, or skip) based on block characteristics such as prediction mode, block size, and coefficient distribution. This dynamic adaptation allows the system to optimize coding efficiency for each block while managing overall device complexity through standardized transform implementations.
3Device complexity
If transform coefficients are zeroed out for large transform blocks, then computational complexity is reduced, but coding efficiency may be affected
Solution Approach 1:
The patent applies local quality by differentiating transform processing based on block size and position. For large transform blocks (e.g., 64×64), the system zeros out high-frequency coefficients in certain regions while preserving low-frequency coefficients. This local differentiation allows the system to reduce computational complexity for large blocks by eliminating obviously insignificant high-frequency data, while maintaining coding efficiency by preserving important low-frequency information that contributes to visual quality.
Data Source
AI summary
Devices, systems and methods for digital video coding, which includes using multiple transforms, are described. In a representative aspect, a method for video processing includes selecting, as part of a multiple transform selection (MTS) process, a common transform as both a vertical transform and a horizontal transform, and applying, as part of performing a conversion between a current block of a video and a bitstream representation of the video, the vertical transform and the horizontal transform to the current block.