Selective Inter-Component Transform for Low-Complexity RGB Coding

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Solution Overview

Problem

Existing image and video coding methods, such as CCLM and JCC, face challenges in efficiently exploiting inter-component redundancy due to computational complexity and inflexibility, particularly for RGB coded content and images with chromatic aberration.

Innovation Solution

Implementing a block-selective inter-component transform (ICT) that allows flexible application of multiple joint coding/decoding methods with explicit or implicit signaling, using orthogonal transforms and downmixing to minimize variance and reduce complexity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a transform is applied to every block in image/video coding, then coding efficiency is improved, but computational complexity increases

Engineering Contradiction:

Improvecoding efficiencyVSAvoidcomputational complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent applies different transform types (DST or DCT) to different blocks based on their local characteristics, specifically the presence of DC coefficients. Blocks with non-zero DC coefficients use DCT, while blocks with zero DC coefficients use DST, optimizing coding efficiency for each local region while avoiding unnecessary computations

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The transform type is dynamically selected based on the block's content characteristics rather than using a fixed transform for all blocks. The encoder determines whether to apply DST or DCT on a per-block basis, allowing the system to adapt to varying block characteristics and improve overall coding efficiency

Inventive Principle:

Principle #15Dynamics

2Ease of manufacture

If DC coefficients are always present in transform blocks, then transform application is simplified, but coding efficiency decreases for blocks without DC components

Engineering Contradiction:

Improvetransform application simplicityVSAvoidcoding efficiency

Core Design Contradiction:

Ease of manufactureVSProductivity

Solution Approach 1:

The patent changes the transform parameter (type selection) based on the DC coefficient value. When the DC coefficient is zero, DST is selected; when non-zero, DCT is selected. This parameter change allows the system to handle blocks without DC components efficiently while maintaining simplicity in the transform application process

Inventive Principle:

Principle #35Parameter changes

3Productivity

If different transform types are used for different blocks, then coding efficiency is improved, but processing complexity increases

Engineering Contradiction:

Improvecoding efficiencyVSAvoidprocessing complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The video stream is segmented into multiple blocks, and each block is independently analyzed for its DC coefficient value. This segmentation allows different transform types to be applied to different segments (blocks) based on their specific characteristics, improving coding efficiency while keeping the decision process simple and localized to each block

Inventive Principle:

Principle #1Segmentation

Data Source

PatentEP3939296B1Selective inter-component transform (ICT) for image and video coding

Publication Date: 2026.05.06 FRAUNHOFER GESELLSCHAFT ZUR FORDERUNG DER ANGEWANDTEN FORSCHUNG EV

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AI summary

An encoder for encoding a plurality of components of an image content region of an image to be encoded is configured for obtaining the plurality of components representing the image content region; selecting an intercomponent transform from a set of intercomponent transforms; encoding the plurality of components using the selected intercomponent transform to obtain encoded components; and providing the encoded components.