Adaptive Reference Sample Filtering for Wide Angle Intra Prediction
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Solution Overview
Problem
Current video coding technologies, such as HEVC and VVC, have limitations in intra prediction modes, particularly for non-square blocks, where conventional angular modes fail to capture wide angular directions effectively, leading to suboptimal filtering of reference samples.
Innovation Solution
The method involves identifying whether an intra prediction mode has a wide angle direction, and if so, using an edge-smoothing filter, or an edge-preserve filter, depending on the block size and direction, to adaptively filter reference samples for accurate prediction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional intra prediction modes are used, then the prediction is simple and fast, but wide angular directions cannot be captured effectively leading to poor prediction accuracy
Solution Approach 1:
The patent applies dynamics by making the filtering process adaptive rather than static. The filter selection (edge-smoothing vs. edge-preserve) dynamically changes based on the intra prediction mode angle, allowing the system to optimize prediction accuracy for different directional scenarios without requiring a fixed complex filtering structure
Solution Approach 2:
The patent changes the filtering parameter based on the prediction mode angle. When the angle exceeds 45 degrees, the system switches from edge-preserve filtering to edge-smoothing filtering, using parameter changes to resolve the contradiction between handling wide angles and maintaining filtering simplicity
2Measurement precision
If edge-smoothing filter is used for wide angle directions, then prediction accuracy improves, but filtering complexity increases
Solution Approach 1:
The patent applies local quality by applying different filtering strategies to different local cases: edge-preserve filtering for conventional angles (≤45°) and edge-smoothing filtering for wide angles (>45°). This localized approach improves reference sample accuracy where needed while avoiding unnecessary complexity in other cases
Solution Approach 2:
The patent uses partial action by applying the more complex edge-smoothing filter only partially - specifically only when the prediction mode angle exceeds 45 degrees. This selective application improves accuracy for wide-angle cases without incurring the full complexity cost for all prediction modes
3Measurement precision
If adaptive filtering based on prediction mode is applied, then prediction quality improves, but processing time increases
Solution Approach 1:
The patent applies preliminary action by determining the appropriate filter type before performing the actual filtering operation. The angle comparison and filter selection are done in advance based on the prediction mode, allowing the subsequent filtering to proceed efficiently without runtime decision-making delays
Data Source
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AI summary
A method of controlling intra prediction for decoding or encoding of a video sequence, is by at least one processor and includes identifying whether an intra prediction mode of a current block has a wide angle direction, based on the intra prediction mode being identified to have the wide angle direction, filtering reference samples of the current block, using an edge-smoothing filter, and based on the intra prediction mode being identified to not have the wide angle direction, filtering the reference samples, using an edge-preserve filter.