Extra-Long Tap Deblocking for Large Smooth Video Blocks
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Solution Overview
Problem
Existing deblocking filters in video coding standards like VVC struggle to effectively handle large smooth blocks due to increased transform sizes, leading to residual block artifacts and inefficiencies in bitrate allocation for smooth areas.
Innovation Solution
An extra-long tap deblocking filter is introduced to address the issue of large smooth blocks, enhancing deblocking performance by applying longer filter lengths and adapting quantization parameters for improved subjective quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If transform size is increased to improve coding efficiency, then coding efficiency is improved, but block artifacts become more prominent in smooth areas
Solution Approach 1:
The patent extends the deblocking filter length parameter from the conventional 7 samples to 15 samples, and in some cases up to 31 samples. This parameter change allows the filter to operate over a larger spatial extent, effectively smoothing block artifacts in smooth areas while preserving coding efficiency gains from large transform sizes.
2Device complexity
If conventional deblocking filter length is used, then processing complexity is low, but block artifacts remain in large smooth blocks
Solution Approach 1:
The patent applies different filter lengths based on local block characteristics. Extra-long tap deblocking (length 15 or 31) is selectively applied to large smooth blocks, while conventional filter lengths are used elsewhere. This local adaptation improves artifact removal where needed while maintaining low complexity in other regions.
3Object-affected harmful factors
If extra-long tap deblocking is applied to all blocks, then block artifacts are reduced, but processing complexity increases
Solution Approach 1:
The patent applies extra-long tap deblocking selectively rather than universally. By using smoothness detection to identify only the blocks that need extended filtering, the solution achieves partial action - applying the computationally intensive operation only where necessary, thus reducing overall processing complexity while still effectively removing artifacts in problematic areas.
4Quantity of substance
If larger transform sizes are used, then bitrate efficiency is improved, but subjective quality in smooth areas deteriorates
Solution Approach 1:
The extended deblocking filter acts as an intermediary between the large transform blocks and the final reconstructed image. It mediates the trade-off by smoothing artifacts introduced by large transforms in smooth areas, thereby improving subjective quality while preserving the bitrate efficiency benefits of using large transform sizes.
Data Source
AI summary
A method for deblocking is provided. The method includes checking whether a size of a current block exceeds a size threshold. The method includes checking whether a size of an adjacent block exceeds the size threshold. The adjacent block is adjacent to a boundary of the current block. The method includes determining that a criteria is true. The criteria comprises both a size of the current block and a size of the adjacent block exceeding the size threshold. The method includes, as a result of determining that the criteria is true, applying a long-tap deblocking across the boundary of the current block. A length of the long-tap deblocking is greater than 7.