Decoder-Side Intra Mode Derivation With Continuous Angle Discretization
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Solution Overview
Problem
Existing video encoding and decoding technologies face challenges in efficiently determining intra prediction modes due to limited context and discontinuities in angle discretization in Decoder Side Intra Mode Derivation (DIMD), leading to suboptimal compression performance.
Innovation Solution
The proposed solution extends the DIMD context to include additional decoded pixels on the above-right and bottom-left sides of the block and implements a continuous angle discretization method to accurately determine the intra prediction mode, using gradients from surrounding reference pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the DIMD context is limited to standard reference pixels, then the device complexity is reduced, but the measurement precision of gradient information deteriorates
Solution Approach 1:
The patent extends the DIMD context from the standard L-shaped reference pixel arrangement to include additional reference pixels in the above-right and bottom-left regions, effectively adding spatial dimensions to the context. This dimensional expansion provides more comprehensive gradient information for intra prediction mode determination without fundamentally changing the processing architecture.
2Manufacturing precision
If angle discretization uses fixed intervals, then the device complexity is reduced, but the manufacturing precision of angle selection deteriorates
Solution Approach 1:
The patent transitions from fixed interval angle discretization to continuous angle discretization, where the angle step size dynamically adapts based on the gradient direction. This parameter change allows for higher precision angle selection in critical regions while maintaining efficiency in less critical regions, resolving the contradiction between precision and complexity.
3Reliability
If additional reference pixels are included in DIMD context, then the reliability of intra prediction mode determination is improved, but the loss of time for processing increases
Solution Approach 1:
The patent performs gradient calculations using the extended reference pixels during the decoding process before final mode selection. By preparing gradient information in advance from the expanded context, the system enables faster and more reliable mode determination without significant additional processing time during critical path operations.
Data Source
AI summary
Decoder side intra mode derivation (DIMD) capability is enhanced by using reference pixels that extend several rows above and several columns left of a current video block, and also includes pixels above and left of the current video block, as well as columns above and right and rows below and left of the current video block. The reference pixels are formed from surrounding reconstructed/previously encoded samples surrounding the current video block. The derivation of an intra prediction mode is determined from gradients determined from each of the reference pixels in a defined surrounding area. In one embodiment, the gradients are determined using horizontal and vertical filters. In a sub-embodiment, the filters do not extend beyond the defined surrounding area. In another embodiment, reassignment of an index indicative of the target intra prediction mode is performed.