VVC Chroma Prediction Using Collocated Luma Block Vectors

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Solution Overview

Problem

In the H.266/VVC standard, the chroma prediction mode for screen content-type video sequences is inaccurate and inefficient due to the use of a fixed DC mode, which fails to utilize information from collocated luma blocks, leading to reduced coding efficiency.

Innovation Solution

The proposed method determines a second block vector parameter for the chroma component based on the block vector parameter of the luma component, utilizing information from collocated luma blocks for improved chroma prediction, thereby enhancing encoding and decoding efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a fixed DC mode is used for chroma prediction in IBC, then the encoding process is simple, but the chroma prediction accuracy is poor and coding efficiency is reduced

Engineering Contradiction:

Improveencoding process simplicityVSAvoidchroma prediction accuracy

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The patent transforms the static fixed DC mode into a dynamic adaptive mode selection mechanism. The chroma prediction mode is dynamically determined based on the luma block's prediction mode (intra, inter, or IBC) and collocated block information, allowing the system to adapt to different content characteristics and achieve optimal prediction accuracy for each case

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the prediction mode parameter based on the luma block type and collocated block availability. Instead of using a fixed DC mode, the system selects from multiple chroma prediction modes (intra, inter, IBC) by changing the mode parameter according to the specific coding context, thereby improving prediction accuracy without significantly complicating the encoding process

Inventive Principle:

Principle #35Parameter changes

2Device complexity

If chroma prediction uses fixed DC mode, then device complexity is low, but coding efficiency is reduced

Engineering Contradiction:

Improveprediction mode complexityVSAvoidcoding efficiency

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The patent performs preliminary determination of chroma prediction mode based on already-decoded luma block information and collocated block data. By using information that is already available from the decoding process, the system avoids complex real-time calculations while achieving improved coding efficiency

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system uses its own decoded luma block information and collocated block data to determine the chroma prediction mode, without requiring external or additional complex processing. The decoding process itself provides the necessary information for mode selection, making the system self-sufficient and avoiding additional complexity

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS20250294167A1Encoding method, decoding method, and decoder

Publication Date: 2025.09.18 GUANGDONG OPPO MOBILE TELECOMMUNICATIONS CORP LTD

AI summary

A decoding method includes: at least one first colour component block of a current block is determined; in response to the at least one first colour component block being intra predicted based on a block vector, at least one second block vector parameter of a second colour component block of the current block is determined based on at least one first block vector parameter of the at least one first colour component block; a prediction value of a second colour component is determined based on the at least one second block vector parameter.