Adaptive Loop Filtering by Temporal Layer for Lower Video Decoding Load
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Solution Overview
Problem
Existing block-based hybrid video coding systems face high computational complexity due to the extensive use of adaptive loop filters (ALFs), particularly in block classification and filtering processes, which hinder efficient compression and decoding of high-resolution video signals.
Innovation Solution
The proposed method reduces computational complexity by selectively applying adaptive loop filtering (ALF) procedures based on temporal layer and gradient calculation, using subsampling techniques for gradient computation and disabling ALF for higher temporal layers, and employing frame-adaptive ALF skip to minimize redundant processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If adaptive loop filtering is applied to all blocks in video coding, then video quality is improved, but computational complexity increases significantly
Solution Approach 1:
The patent applies ALF selectively to specific blocks based on their characteristics rather than uniformly to all blocks. Block classification identifies regions that benefit from filtering, applying ALF only where needed to maintain video quality while reducing overall computational complexity.
Solution Approach 2:
The patent uses subsampling techniques to compute gradients at reduced resolution, performing partial gradient calculations that are sufficient for block classification decisions. This partial action reduces the number of computations required while maintaining adequate filtering performance.
2Measurement precision
If gradient calculation is performed for all pixels in block classification, then filtering accuracy is improved, but processing time increases
Solution Approach 1:
The patent calculates gradients only for a subset of pixels rather than all pixels in the block. This partial gradient calculation provides sufficient accuracy for block classification while significantly reducing the number of operations and processing time required.
Solution Approach 2:
The patent divides the block processing into segments, applying gradient calculation only to selected regions or pixel subsets. This segmentation approach maintains filtering accuracy for critical areas while avoiding redundant calculations in other regions.
3Manufacturing precision
If ALF is applied to all temporal layers, then video quality is maintained, but redundant processing occurs in higher temporal layers
Solution Approach 1:
The patent dynamically adjusts ALF application based on temporal layer characteristics. Higher temporal layers with motion-compensated prediction are identified as having reduced benefit from ALF, so filtering is adaptively disabled for these layers, eliminating redundant processing while maintaining quality where it matters.
Data Source
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AI summary
Systems, methods and instrumentalities are disclosed for adaptively selecting an adaptive loop filter (ALF) procedure for a frame based on which temporal layer the frame is in. ALF procedures may vary in computational complexity. One or more frames including the current frame may be in a temporal layer of a coding scheme. The decoder may determine the current frame's temporal layer level within the coding scheme. The decoder may select an ALF procedure based on the current frame's temporal layer level. If the current frame's temporal layer level is higher within the coding scheme than some other temporal layer levels, an ALF procedure that is less computationally complex may be selected for the current frame. Then the decoder may perform the selected ALF procedure on the current frame.