Multilayer Video Coding ALF APS Management

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Solution Overview

Problem

Existing video coding standards like VVC face challenges in efficiently managing Adaptive Loop Filters (ALF) in multilayer coding scenarios, leading to inter-layer conflicts and reduced coding efficiency when handling subpictures or multiple layers in video content.

Innovation Solution

Implementing a restricted alf_aps_id space per layer and using layer_id to uniquely identify ALF APSs, ensuring no inter-layer conflicts by defining alf_aps_id ranges specific to each layer, and signaling layer-dependent ALF filter sets.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a shared alf_aps_id space is used across multiple layers, then device complexity is reduced, but inter-layer conflicts occur and coding efficiency deteriorates

Engineering Contradiction:

ImproveALS APS management complexityVSAvoidcoding efficiency

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The patent segments the shared alf_aps_id space into layer-specific ranges, where each layer is assigned a dedicated range of alf_aps_id values. This segmentation prevents inter-layer conflicts by ensuring that different layers use distinct identifier ranges, thereby resolving the contradiction between reduced complexity and maintained coding efficiency.

Inventive Principle:

Principle #1Segmentation

2Productivity

If layer-dependent ALF filter sets are signaled for each layer, then coding efficiency is enhanced, but device complexity increases

Engineering Contradiction:

Improvecoding efficiencyVSAvoidALS APS signaling complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent applies local quality by making ALF filter set signaling layer-dependent. Each layer can independently signal its own alf_aps_id values within its assigned range, allowing optimized filtering for specific layer characteristics while maintaining overall system organization through the hierarchical layer structure.

Inventive Principle:

Principle #3Local quality

3Reliability

If alf_aps_id ranges are restricted per layer, then inter-layer conflicts are prevented, but adaptability across layers is reduced

Engineering Contradiction:

Improveconflict preventionVSAvoidcross-layer adaptability

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent resolves this contradiction by adding a layer dimension to the alf_aps_id selection process. While each layer is restricted to its specific range (ensuring reliability), the system maintains cross-layer adaptability by allowing flexible selection within the constrained range and enabling different layers to use different filter sets appropriate to their specific requirements.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Data Source

PatentUS20250317584A1ALF APSs FOR MULTILAYER CODING AND DECODING

Publication Date: 2025.10.09 INTERDIGITAL CE PATENT HOLDINGS SAS

AI summary

A restricted syntax range per layer in a multi-layer video coding scheme prevents inter-layer conflicts. In one embodiment, adaptive loop filtering sets defined in an adaptive parameter set are distinct in the multiple layers. In another embodiment, a layer identification is also used to uniquely identify the adaptation parameter set. In a related embodiment, a high-level syntax flag indicates whether a layer is independent of other layers.