Intra Prediction Mode Mapping for Non-Square VVC Blocks

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 prediction accuracy due to non-square blocks and the borrowing of luma block modes in chroma prediction, 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 unifying mode representation across different block shapes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If wide angular modes are used in luma prediction to reduce bits for entropy coding, then coding efficiency is improved, but angular mode representation accuracy deteriorates due to deviations in actual angle directions

Engineering Contradiction:

Improvecoding efficiencyVSAvoidangular mode representation accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent applies parameter changes by introducing a mapping relationship between angular mode indices and actual angle directions. Different angular mode indices are mapped to different actual angle directions based on the width-height ratio of the block. This allows the system to maintain coding efficiency while improving angular mode representation accuracy through parameter transformation.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent implements dynamics by making the angular mode mapping adaptive to different block shapes. The mapping relationship changes dynamically based on the width-height ratio of the processed block, allowing the system to adjust angular mode representation according to the specific geometric characteristics of each block.

Inventive Principle:

Principle #15Dynamics

2Device complexity

If chroma prediction borrows luma block prediction modes, then chroma prediction complexity is reduced, but prediction accuracy deteriorates due to deviations in angular mode correspondence

Engineering Contradiction:

Improveprediction process complexityVSAvoidprediction accuracy

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent introduces an intermediary mapping mechanism that bridges luma and chroma prediction processes. This mapping relationship serves as a mediator to ensure accurate correspondence between angular modes in luma blocks and chroma blocks, resolving the accuracy issue while maintaining the simplicity of mode borrowing.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent applies parameter changes by establishing a specific mapping between angular mode indices of luma blocks and chroma blocks. This parameter transformation ensures that when chroma prediction borrows luma modes, the angular mode correspondence remains accurate, thereby improving prediction reliability without increasing complexity.

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If angular modes are represented by fixed indices, then encoding simplicity is maintained, but angle conversion becomes complicated for non-square blocks

Engineering Contradiction:

Improveencoding simplicityVSAvoidangle conversion complexity

Core Design Contradiction:

Ease of manufactureVSDevice complexity

Solution Approach 1:

The patent implements dynamics by making the angular mode mapping adaptive to different block shapes. The mapping relationship changes dynamically based on the width-height ratio of the processed block, allowing the system to adjust angular mode representation according to the specific geometric characteristics of each block.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent applies parameter changes by introducing a mapping relationship between angular mode indices and actual angle directions. Different angular mode indices are mapped to different actual angle directions based on the width-height ratio of the block. This allows the system to maintain coding efficiency while improving angular mode representation accuracy through parameter transformation.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS20250365443A1Intra prediction method and device and computer-readable storage medium

Publication Date: 2025.11.27 GUANGDONG OPPO MOBILE TELECOMMUNICATIONS CORP LTD

AI summary

A method for intra prediction and a decoder are provided. The method includes the following operations. At least one neighbouring block of a current block is determined. A first intra prediction mode index of the at least one neighbouring 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.