Intra Prediction Mode Mapping for Non-Square VVC Blocks
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Solution Overview
Problem
In the luma and chroma prediction processes of the next generation video coding standard H.266/VVC, the use of wide angular modes leads to deviations in angular mode representation, affecting the accuracy of intra prediction due to non-square blocks and the borrowing of prediction modes, which complicates angle conversion and results in inaccurate prediction.
Innovation Solution
An intra prediction method that configures actual angular modes using relative angle numbers, determined by preset angle sampling points and width-height relationships, ensuring a one-to-one correspondence with actual angular modes, thereby simplifying angle conversion and eliminating deviations in luma and chroma prediction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If wide angular modes are used in non-square blocks, then prediction direction coverage is improved, but angular mode representation accuracy deteriorates due to deviation between angular mode index and actual angle direction
Solution Approach 1:
The patent introduces a mapping relationship between angular mode indices and actual angle directions, adjusting the parameter interpretation based on block shape and position. For non-square blocks, the angular mode index is adjusted according to the block's width-height ratio to accurately represent the actual prediction direction, thereby resolving the representation accuracy issue while maintaining wide angular mode coverage.
2Productivity
If direct mode borrows luma block prediction mode, then chroma prediction efficiency is improved, but prediction accuracy deteriorates due to deviation in angular mode representation
Solution Approach 1:
The patent introduces an intermediary mapping mechanism that translates the borrowed luma block's angular mode index into the correct chroma block angular mode index. This intermediary adjustment ensures that the borrowed prediction mode accurately represents the chroma block's actual prediction direction, maintaining both efficiency and accuracy.
3Device complexity
If angular mode index is used directly without adjustment, then coding complexity is reduced, but prediction accuracy deteriorates due to angle conversion complications
Solution Approach 1:
The patent performs preliminary adjustment of angular mode indices based on block shape and position before the prediction process. By pre-establishing the mapping relationships between angular mode indices and actual angle directions, the system avoids complex angle conversions during coding while ensuring accurate prediction representation.
Data Source
AI summary
A method for intra prediction and a non-volatile computer-readable storage medium are provided. The method includes the following operations. A first intra prediction mode index of at least one neighbouring block of a current block is determined. An intra prediction mode list is constructed based on the first intra prediction mode index of the at least one neighbouring block. A first intra prediction mode index of the current block is determined based on the intra prediction mode list. A width to height ratio of the current block is obtained, and the first intra prediction mode index is mapped to a second intra prediction mode index according to the width to height ratio. Prediction is performed for the current block based on a target intra prediction mode, and a prediction block is obtained. A reconstruction block of the current block is obtained.