Inter-Predicted Transform Block Deblocking With Adaptive Boundary Strength
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Solution Overview
Problem
Conventional deblocking filters fail to effectively address discontinuities at edges between transform/coding blocks, particularly those using inter prediction, leading to visible artifacts in video coding.
Innovation Solution
Introduce a deblocking filter apparatus and methods that apply deblocking processes to transform block boundaries within coding blocks, especially when sub block transform (SBT) is used, by determining a boundary strength parameter and performing filtering based on this parameter to mitigate or remove blocking artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional deblocking filters are applied to transform block boundaries, then blocking artifacts are reduced, but visible discontinuities remain at edges between transform blocks using inter prediction
Solution Approach 1:
The patent applies different boundary strength values (BS=0, BS=1, or BS=2) to different transform block boundaries based on local characteristics. Specifically, boundaries between transform blocks using inter prediction are assigned BS=0 to prevent excessive filtering that would create discontinuities, while other boundaries receive appropriate filtering strength. This localized differentiation resolves the contradiction by adapting filter strength to local block characteristics rather than applying uniform filtering.
Solution Approach 2:
The boundary strength parameter is dynamically determined based on the prediction mode of adjacent transform blocks. The patent introduces conditional logic that adjusts BS values according to whether blocks use intra or inter prediction, making the filtering process adaptive rather than static. This dynamic adjustment allows the filter to maintain effectiveness while avoiding artifacts specific to inter-predicted blocks.
2Object-affected harmful factors
If deblocking filtering is performed on all transform block boundaries, then edge artifacts are reduced, but coding efficiency decreases due to increased processing complexity
Solution Approach 1:
The patent applies deblocking filtering selectively rather than universally. By identifying specific boundary conditions (inter prediction mode) where filtering should be avoided or reduced, the patent performs partial filtering action. This approach removes edge artifacts where necessary while skipping filtering in cases where it would be ineffective or harmful, thereby maintaining coding efficiency without sacrificing artifact reduction where it matters.
Solution Approach 2:
The patent changes the boundary strength parameter based on transform block characteristics, specifically setting BS=0 for boundaries between inter-predicted blocks. This parameter modification optimizes the filtering process by adjusting its intensity according to local conditions, reducing unnecessary processing operations and improving overall coding efficiency while maintaining artifact reduction effectiveness.
Data Source
AI summary
A deblocking method, for deblocking a transform block boundary within a coding block in an image encoding and/or an image decoding is provided, wherein the coding block comprising transform blocks is coded in inter prediction mode and the transform blocks comprises a first transform block and a second transform block. The method comprises: determining, when the boundary between the first transform block and the second transform block is a transform block boundary and at least one of the first transform block and the second transform block has one or more non-zero transform coefficients, a value of a BS parameter for the boundary between the first transform block and the second transform block to be a first value; and performing de-blocking filtering process to the boundary between the first transform block and the second transform block at least based on the value of the boundary strength parameter.