Loop Restoration Boundary Filtering for Video Coding
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Solution Overview
Problem
Existing video coding technologies face inefficiencies in handling boundary pixel values during intra prediction and motion compensation, leading to suboptimal compression ratios and quality in video encoding and decoding processes.
Innovation Solution
Implementing a non-linear mapping based filter, such as a cross-component sample offset (CCSO) or local sample offset (LSO) filter, to buffer and process boundary pixel values within a loop filter chain, enhancing the application of loop restoration filters for improved video encoding and decoding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional intra coding and motion compensation are used, then video coding can be performed with basic compression, but the compression ratio and video quality are suboptimal due to inefficiencies in boundary pixel handling
Solution Approach 1:
The patent applies loop restoration filters before the final reconstruction of video blocks, performing boundary pixel optimization in advance. The filter chain processes boundary pixels between blocks to reduce artifacts and improve quality before the blocks are fully reconstructed and used for prediction, thereby achieving better compression ratios without sacrificing video quality
Solution Approach 2:
The patent introduces an intermediate filtering stage with loop restoration filters that operate on boundary pixels between reconstructed blocks. This intermediary processing step refines the boundary pixel values before they are used in subsequent prediction and reconstruction operations, resolving the contradiction by improving both compression efficiency and visual quality through intermediate optimization
2Productivity
If loop restoration filters are applied without optimized boundary pixel handling, then the filtering process is simpler, but the compression ratio and overall video quality remain suboptimal
Solution Approach 1:
The patent segments the filtering process into distinct stages: a first loop restoration filter that processes boundary pixels, followed by a second loop restoration filter that processes the filtered boundary pixels again. This segmentation allows each filter to specialize in specific aspects of boundary optimization, improving encoding efficiency while managing complexity through modular design
Solution Approach 2:
The patent implements a dynamic filter chain where the second loop restoration filter operates on the output of the first filter. The filtering process adapts to the characteristics of the boundary pixels through multiple passes, with each filter stage adjusting its operation based on the input from the previous stage, thereby optimizing video quality without requiring excessively complex single-stage filters
Data Source
AI summary
In a method for filtering in video coding, first boundary pixel values of a subset of first reconstructed samples are buffered at a first node in a loop filter chain, a first filter and a second filter being applied to the first boundary pixel values, the first boundary pixel values being values of pixels at a frame boundary. Second boundary pixel values of a subset of second reconstructed samples are buffered at a second node in the loop filter chain, the second boundary pixel values being values of the pixels at the frame boundary. A loop restoration filter is applied on to-be filtered reconstructed samples based on the buffered first boundary pixel values of the subset of the first reconstructed samples and the buffered second boundary pixel values of the subset of the second reconstructed samples.