Secondary Transform for Energy Compaction in Intra Video Coding
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Solution Overview
Problem
Existing video encoding and decoding technologies face challenges in achieving high compression efficiency, particularly in intra sub-block partitions, as they often rely on conventional transforms that do not fully exploit the energy compaction of transform coefficients.
Innovation Solution
Implementing a secondary transform, such as the Low-Frequency Non-Separable Transform (LFNST), for coding units in intra sub-partition mode, allowing for enhanced energy compaction of transform coefficients and improved entropy coding efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional transform is used for intra sub-block partition coding, then the encoding process is simple, but compression efficiency is insufficient
Solution Approach 1:
The patent segments the transform processing into two distinct stages: a primary transform that processes the entire residual block, and a secondary transform that processes specific sub-regions. This segmentation allows the system to apply complex processing only where needed (in regions with horizontal or vertical gradients), thereby improving compression efficiency without uniformly increasing complexity across the entire block.
Solution Approach 2:
The patent applies different transform strategies to different regions of the residual block based on local characteristics. The secondary transform is selectively applied to sub-blocks identified as having horizontal or vertical gradients, while other regions use only the primary transform. This local differentiation optimizes compression efficiency for gradient regions without unnecessarily complicating the processing of uniform regions.
2Productivity
If a secondary transform is applied to all transform units, then energy compaction is improved, but computational complexity increases
Solution Approach 1:
The patent implements partial application of the secondary transform by first applying a primary transform to the entire residual block, then selectively applying the secondary transform only to specific sub-blocks that exhibit horizontal or vertical gradient characteristics. This partial action approach achieves energy compaction improvement where needed while avoiding the excessive computational cost of applying the secondary transform uniformly across all transform units.
Solution Approach 2:
The patent changes the processing parameters dynamically based on the characteristics of each sub-block. By detecting whether a sub-block contains horizontal or vertical gradients and adjusting the transform application accordingly, the system optimizes energy compaction for gradient regions while reducing computational power consumption for uniform regions.
Data Source
AI summary
A method and apparatus for encoding/decoding a picture use a secondary transform for video encoding and decoding in INTRA mode and more particularly use a secondary transform for the transform units of a coding unit in intra sub partition mode. Different signaling and selection variants are proposed according to various parameters of the coding unit and transform unit.