Intra Prediction Mode Derivation for Transform and MPM Selection
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Solution Overview
Problem
Existing video coding technologies face inefficiencies in deriving intra prediction modes for coding blocks, particularly when conventional modes are not applicable, leading to suboptimal compression and decoding performance.
Innovation Solution
The proposed method involves deriving a second intra prediction mode from a pre-defined region that includes current and previously coded coding tree units, updating this region as needed, and using this mode to select transforms and construct most probable mode lists, while handling candidate blocks outside the region by substitution or skipping, thereby enhancing intra prediction accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional intra prediction modes are used for coding blocks, then the decoding process is simple, but the prediction accuracy deteriorates when conventional modes are not applicable
Solution Approach 1:
The system automatically determines whether a candidate block is coded with an unconventional intra prediction mode and derives a corresponding conventional intra prediction mode without external intervention. This self-service mechanism resolves the contradiction by enabling accurate prediction only when needed, rather than applying complex procedures universally.
Solution Approach 2:
The patent applies different processing strategies to different regions: candidate blocks within the pre-defined region undergo mode derivation while those outside do not. This local differentiation optimizes prediction accuracy for blocks that need it while avoiding unnecessary complexity for blocks that don't, resolving the contradiction between accuracy and complexity.
2Productivity
If a pre-defined region is used to select candidate blocks for mode derivation, then the processing is efficient, but prediction accuracy deteriorates for blocks outside the region
Solution Approach 1:
The system performs mode derivation only for a subset of candidate blocks (those within the pre-defined region) rather than all candidate blocks. This partial action maintains processing efficiency while achieving sufficient prediction accuracy for the most critical blocks, resolving the contradiction between efficiency and accuracy.
3Loss of energy
If unconventional intra prediction modes are directly used, then the compression performance is improved, but compatibility with standard transforms deteriorates
Solution Approach 1:
The patent introduces a conventional intra prediction mode as an intermediary between unconventional modes and standard transforms. This intermediary enables blocks coded with unconventional modes to use standard transforms by providing a bridge that maintains both compression performance and transform compatibility, resolving the contradiction.
Solution Approach 2:
The system changes the parameter representation by deriving a conventional intra prediction mode index from unconventional mode information. This parameter transformation allows the block to be processed using standard transform procedures while preserving the benefits of unconventional prediction, resolving the compatibility issue.
Data Source
AI summary
Aspects of the disclosure include methods and an apparatus for video coding. The apparatus includes processing circuitry that receives coded information of a current block in a current picture. The current block is coded with a first intra prediction mode that is different from a plurality of intra prediction modes including a DC mode, a Planar mode, and angular intra prediction modes. A candidate block in the current picture coded by an intra prediction mode different from the plurality of intra prediction modes is selected. If the candidate block is located within a pre-defined region, a second intra prediction mode is derived from the plurality of intra prediction modes for the candidate block. The second intra prediction mode is associated with the current block and is used to select a transform for the current block and/or to construct a most probable mode (MPM) list for another block.