Adaptive Loop Filtering After Fixed Filtering for VVC Artifacts
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Solution Overview
Problem
Existing video coding technologies face challenges in effectively addressing residual artifacts and noise in compressed video data, particularly in advanced standards like Versatile Video Coding (VVC), where traditional loop filters may not adequately adapt to the complexity and variability of video content.
Innovation Solution
Implementing adaptive loop filtering (ALF) techniques that apply both fixed and adaptive filters with changeable coefficients to enhance the filtering process, allowing for more precise and context-aware enhancement of video quality, particularly through the use of block-based and cross-component ALF methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional loop filters are used in video coding, then device complexity is reduced, but video quality and artifact reduction capability deteriorate
Solution Approach 1:
The filtering process is divided into multiple independent filter stages, each handling specific types of artifacts. The first filter processes certain frequency components while the second filter handles residual artifacts, allowing each filter to be optimized for its specific function without requiring excessive complexity in a single filter design.
Solution Approach 2:
Filters are applied in a nested sequence where the output of the first filter becomes the input to the second filter. This nested filtering approach enables progressive refinement of video quality, with each filter building upon the work of the previous filter to achieve superior artifact reduction.
2Adaptability or versatility
If fixed filter coefficients are used, then device complexity is reduced, but adaptability to diverse video content deteriorates
Solution Approach 1:
The system transitions from static fixed coefficients to dynamic adaptive coefficients that change based on the characteristics of the video content being processed. The filter coefficients are adjusted according to local image properties such as edge strength and texture, enabling the filter to adapt to diverse video content while maintaining manageable complexity through structured adaptation rules.
3Manufacturing precision
If multiple filtering stages are applied, then residual artifact reduction is improved, but processing time increases
Solution Approach 1:
The filtering system applies multiple stages but strategically terminates or reduces filtering in regions where it is not needed, such as flat areas or already well-filtered regions. This partial application approach maintains high artifact reduction capability in problematic areas while minimizing processing time in benign areas.
Solution Approach 2:
Different filtering strengths and types are applied to different regions of the video content based on local characteristics. Areas with strong edges or textures receive appropriate filtering while preserving detail, whereas smooth areas receive minimal processing, optimizing the balance between artifact reduction and processing efficiency.
Data Source
AI summary
An apparatus includes processing circuitry that receive a bitstream including a picture. The processing circuitry applies one or more first fixed filters with constant filter coefficients to samples in the picture to obtain one or more respective first filtered outputs of the samples in the picture. Subsequent to applying the one or more first fixed filters, the processing circuitry applies one or more second adaptive filters with changeable coefficients to the one or more first filtered outputs to obtain a second filtered sample of a current sample in the samples and decodes the picture based at least on the second filtered sample of the current sample in the picture. Each coefficient of the second adaptive filter can be applied to a corresponding one of the one or more first filtered outputs.