Intra Sharpening and De-ringing Filter for Video Coding
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Solution Overview
Problem
Conventional video coding standards, such as H.264/AVC and H.265/HEVC, face challenges in preserving natural edges during intra frame prediction, leading to blurring and ringing effects due to quantization matrices, which can be exacerbated by attempts to suppress ringing with linear smoothing filters.
Innovation Solution
A decoder and encoder system that selectively applies sharpening and de-ringing filters based on flags in the bitstream, allowing for improved prediction efficiency and image quality by filtering reference samples before generating prediction blocks, and optionally using smoothing filters to avoid opposing actions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If linear smoothing filters are applied to suppress ringing effects, then ringing artifacts are reduced, but natural edges become blurred
Solution Approach 1:
The patent applies different filtering operations to different regions of the image based on local characteristics. Edge regions are identified and processed differently from non-edge regions, allowing ringing suppression in smooth areas while preserving edge sharpness through selective filter application.
Solution Approach 2:
Instead of applying smoothing filters to reduce ringing (which blurs edges), the patent inverts the approach by applying sharpening filters to enhance edges. This counterintuitive method compensates for the blurring effect of quantization and smoothing while maintaining ringing suppression through adaptive processing.
2Stability of the object's composition
If quantization matrices are used to preserve low frequency components, then low frequency information is maintained, but errors increase for blocks containing natural edges resulting in blurring and ringing
Solution Approach 1:
The patent dynamically changes filtering parameters based on the characteristics of the image block being processed. By analyzing edge content and block properties, the system adjusts filter strength and type to optimize the balance between low-frequency preservation and edge accuracy, rather than using fixed quantization matrices.
Solution Approach 2:
The filtering process transitions from static quantization matrices to dynamic adaptive filtering. The system continuously adjusts filter parameters based on local image characteristics, allowing it to respond to varying edge content and block properties throughout the video sequence.
3Productivity
If conventional intra prediction is used, then coding efficiency is maintained, but distortion of natural edges occurs in prediction blocks
Solution Approach 1:
The patent applies sharpening and de-ringing filters to reference samples before they are used for intra prediction. This preliminary processing of reference data improves the quality of the prediction block by pre-correcting edge distortions, leading to better prediction accuracy and reduced residuals without significantly increasing computational complexity.
Data Source
AI summary
A decoder for decoding a block of a current frame of a video from a bitstream, the decoder comprising a reference sample selection unit configured to select reference samples of a reconstructed part of the current frame, a filter unit configured to filter the reference samples, and a block generation unit configured to generate a prediction of the block based on the filtered reference samples, wherein the filter unit comprises a sharpening filter and/or a de-ringing filter to be applied based on a flag in the bitstream.