Aspect-Ratio Directional Intra-Prediction for Rectangular Blocks
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Solution Overview
Problem
The existing QTBT partitioning framework in video coding standards does not adequately account for the asymmetry of rectangular blocks, leading to inefficient handling of directional intra-prediction modes due to the same number of reference samples being used along both shorter and longer sides, regardless of aspect ratio or availability.
Innovation Solution
An apparatus and method that extend the set of directional intra-prediction modes based on the aspect ratio of a block, enabling or disabling modes based on reference sample availability, and signaling these modes through mode mapping and a one-bit flag.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the same number of reference samples are used along both shorter and longer sides of rectangular blocks, then the implementation is simple, but the coding efficiency is reduced due to not accounting for block asymmetry
Solution Approach 1:
The patent applies asymmetry by differentiating the handling of reference samples based on block aspect ratio. For rectangular blocks, different numbers of reference samples are used along the shorter side versus the longer side, matching the actual geometric asymmetry of the block and improving prediction accuracy without excessive complexity
Solution Approach 2:
The patent applies local quality by adapting the prediction mode set locally according to the specific aspect ratio of each block. Different directional intra-prediction modes are enabled or disabled based on the local geometric characteristics of each rectangular block, allowing optimal prediction for each region
2Productivity
If the set of directional intra-prediction modes is extended to account for block asymmetry, then coding efficiency is improved, but the device complexity increases
Solution Approach 1:
The patent applies dynamics by making the set of available directional intra-prediction modes dynamic rather than static. The apparatus selectively enables or disables specific prediction modes based on the aspect ratio of the current block, adapting the complexity to the actual need rather than always maintaining the maximum mode set
Solution Approach 2:
The patent applies parameter changes by modifying which prediction modes are available based on the aspect ratio parameter of the block. This conditional parameter change allows the system to improve coding efficiency for rectangular blocks while avoiding unnecessary complexity for square blocks where the extended modes would not provide benefit
Data Source
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AI summary
The invention relates to an intra-prediction apparatus (100) for extending a set of predetermined directional intra-prediction modes of a rectangular video coding block. The intra-prediction apparatus (100) comprises an aspect ratio determining unit (101) configured to determine an aspect ratio of the rectangular video coding block, a complementary angle range determining unit (103) configured to determine a complementary angle range upon the basis of the aspect ratio, a directional intra-prediction mode extending unit (105) configured to select a complementary direction within the complementary directional range, and to add an extension directional intra-prediction mode being associated with the complementary direction to the set of predetermined directional intra-prediction modes, and an intra-prediction unit (107) configured to intra-predict pixel values of pixels of the rectangular video coding block on the basis of the extension directional intra-prediction mode.