Non-Square Intra Prediction Mode Remapping for Video Coding
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Solution Overview
Problem
Existing video coding technologies face inefficiencies in handling non-square blocks due to the limited set of intra prediction modes, which can lead to increased bit usage for less likely prediction directions, thereby reducing compression efficiency.
Innovation Solution
The proposed solution involves remapping intra prediction modes from a first set designed for square blocks to a second set tailored for non-square blocks, considering the aspect ratio and disabling certain modes based on the block shape, and adjusting mode numbers to achieve a more efficient mapping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a limited set of intra prediction modes is used for non-square blocks, then device complexity is reduced, but compression efficiency deteriorates due to increased bit usage for less likely prediction directions
Solution Approach 1:
The patent changes the parameter of intra prediction mode selection by introducing aspect ratio-based classification. Blocks are categorized into square, wide, and tall types, and each category is assigned a tailored set of intra prediction modes. This parameter change allows the system to optimize the number and type of prediction modes according to block geometry, reducing unnecessary mode evaluations for non-square blocks while maintaining compression efficiency through appropriate mode selection.
2Loss of information
If intra prediction modes are remapped based on aspect ratio, then compression efficiency is improved, but device complexity increases due to additional mode mapping logic
Solution Approach 1:
The patent applies preliminary action by pre-defining aspect ratio thresholds and corresponding intra prediction mode sets before the actual coding process. The aspect ratio thresholds are determined in advance, and the mapping between aspect ratio ranges and intra prediction mode categories is established beforehand. This preliminary preparation simplifies the runtime decision-making process, as the encoder only needs to compare the block's aspect ratio against pre-computed thresholds to select the appropriate mode set, rather than performing complex real-time analysis.
3Quantity of substance
If certain intra prediction modes are disabled based on block shape, then bit usage is reduced for less likely directions, but adaptability deteriorates
Solution Approach 1:
The patent applies local quality by customizing the intra prediction mode availability according to the local characteristics of each block, specifically its aspect ratio. Instead of using a uniform mode set for all blocks, the system assigns different mode configurations to different block types: square blocks receive the full mode set, while wide and tall blocks receive specialized subsets. This local customization ensures that each block type has access to the most appropriate prediction modes for its geometry, improving compression efficiency without sacrificing necessary adaptability.
Data Source
AI summary
Aspects of the disclosure provide method and apparatus for video coding. In some examples, an apparatus includes processing circuitry. The processing circuitry decodes prediction information of a first block from a coded video bitstream. The first block is a non-square block and the prediction information for the first block is indicative of a first intra prediction mode in a first set of intra prediction modes for a square block. Then, the processing circuitry remaps the first intra prediction mode to a second intra prediction mode in a second set of intra prediction modes that is used for the non-square block. The second set of intra prediction modes includes at least the second intra prediction mode that is not in the first set of intra prediction modes. Further, the processing circuitry reconstructs at least one sample of the first block according to the second intra prediction mode.