MPM List Construction with Offset Candidates for Non-Square Blocks
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Solution Overview
Problem
The existing video coding standards, such as VVC, face challenges in efficiently constructing the Most Probable Modes (MPM) list, particularly in handling non-square blocks and wide-angle intra prediction modes, which affect coding efficiency.
Innovation Solution
The method involves generating alternative candidates for the MPM list by adding offset distances to the initial MPM candidates, with constraints based on block size, aspect ratio, or template matching costs, and applying decoder-side intra mode derivation (DIMD) to enhance the MPM list construction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the initial MPM list construction method is used, then the coding process is simple, but the coding efficiency is insufficient for non-square blocks and wide-angle intra prediction modes
Solution Approach 1:
The patent applies preliminary action by pre-defining offset distance sets based on block aspect ratios before the actual MPM list construction. These offset sets are prepared in advance according to different block shapes (square, wide, tall), allowing the encoder to quickly select appropriate candidates without complex real-time calculations during mode selection, thus improving coding efficiency while maintaining manageable complexity
Solution Approach 2:
The patent implements local quality by tailoring the MPM list construction process to specific block characteristics. Different offset distance sets are applied based on the local block shape (square, wide, or tall), ensuring that each block type receives optimized candidates suited to its geometry. This localized approach improves coding efficiency for non-square blocks without unnecessarily complicating the overall system
2Measurement precision
If more MPM candidates are added to improve accuracy, then the prediction accuracy improves, but the computational complexity increases
Solution Approach 1:
The patent applies parameter changes by systematically varying the offset distances based on block aspect ratio parameters. Instead of adding all possible candidates uniformly, the method adjusts the offset values (e.g., ±1, ±2, ±4, ±8) according to the block shape parameters, creating an adaptive candidate selection process that improves prediction accuracy while controlling computational complexity through parameter-based filtering
Solution Approach 2:
The patent uses partial action by selectively adding only the necessary MPM candidates based on block characteristics rather than exhaustively evaluating all possible intra prediction modes. The method adds a limited number of offset-based candidates (typically 2-4 per base mode) which is sufficient to capture the dominant prediction directions for each block type without the full computational burden of exhaustive search
Data Source
AI summary
A method and apparatus for alternative derived modes in MPM list construction in video coding. According to the method, an initial MPM (Most Probable Modes) list, comprising comprises MPM1 candidate and MPM2 candidate is determined for the current block. Alternative first candidates are generated by adding one or more first offset distances to the MPM1 candidate. Alternative second candidates are generated by adding one or more second offset distances to the MPM2 candidate. At least one of the alternative first candidates and at least one of alternative second candidates are inserted into the initial MPM list to form an extended MPM list. At least one of alternative first candidates and at least one of alternative second candidates are inserted into the initial MPM according to associated offset distances. The current block is encoded or decoded using information comprising the extended MPM list.