Two-Stage Adaptive Loop Filter for Video Decoding
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Solution Overview
Problem
Current video decoding techniques face limitations in improving the quality of decoded video data, as single-stage adaptive loop filtering (ALF) fails to effectively account for local features of video data.
Innovation Solution
A video decoder is configured to perform two stages of adaptive loop filtering, determining activity and direction values for reconstructed samples to select appropriate filters from predefined sets, applying these filters to improve the quality of decoded video data by accounting for local features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single-stage adaptive loop filter is applied to decoded video data, then the filtering process is simple and fast, but the quality of decoded video data is insufficient because local features are not effectively accounted for
Solution Approach 1:
The adaptive loop filtering process is divided into two distinct stages: a first stage that applies a first filter to the decoded video data, and a second stage that applies a second filter to the intermediate results. This segmentation allows each stage to focus on specific local features independently, improving overall quality while maintaining manageable complexity through modular processing.
Solution Approach 2:
The invention adds a temporal dimension to the filtering process by introducing a second filtering stage that operates on the output of the first stage. This multi-stage approach transforms a single-pass filter into a sequential two-pass system, enabling more sophisticated handling of local features without requiring a single overly complex filter.
2Manufacturing precision
If a two-stage adaptive loop filtering is applied to account for local features, then the quality of decoded video data is improved, but the filtering process becomes more complex
Solution Approach 1:
Each filtering stage is configured to handle specific local features of the video data independently. The first filter and second filter can be designed with different characteristics optimized for different types of local variations, allowing the system to account for diverse local features without requiring a single universally complex filter.
Solution Approach 2:
The first filtering stage performs preliminary processing on the decoded video data, preparing it for the second stage. This preliminary action allows the second filter to focus on refining specific aspects of the data, dividing the complex task of quality improvement into manageable sequential steps rather than requiring one overly complex simultaneous operation.
Data Source
AI summary
A video decoder can be configured to apply a first stage adaptive loop filter (ALF) to a reconstructed sample by determining a first class index for the reconstructed sample, selecting a filter from a first set of filters based on the first class index, and applying the filter from the first set of filters to the reconstructed sample to determine a first intermediate sample value; apply a second stage ALF to the reconstructed sample by determining a second class index for the reconstructed sample; select a second filter from a second set of filters based on the second class index, applying the second filter to the reconstructed sample to determine a first sample modification value, and determining a second sample modification value based on the first intermediate sample value; and determine a filtered reconstructed sample based on the reconstructed sample and the first and second sample modification values.