Adaptive Loop Filter Scaling Across Temporal Video Layers

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Solution Overview

Problem

In video coding, encoder/decoder mismatch occurs when not all temporal layers of a temporally scalable bitstream are received, leading to issues with adaptive loop filtering due to missing scaling factors.

Innovation Solution

A video encoder and decoder store scaling factors in a buffer for future usage based on the second temporal layer ID being less than or equal to the first temporal layer ID, ensuring consistent filtering even if not all temporal layers are received.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If scaling factors are stored in a buffer for future usage based on temporal layer ID comparison, then encoder/decoder mismatch is prevented and filtering consistency is maintained, but device complexity increases due to buffer management requirements

Engineering Contradiction:

Improveencoder/decoder consistencyVSAvoidbuffer management complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies preliminary action by storing scaling factors in a buffer in advance, before they are needed for filtering operations. When a scaling factor is signaled in temporal layer N, it is proactively stored and made available for future use in temporal layers N-1 and earlier, preventing encoder/decoder mismatch without requiring complex real-time coordination

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The buffer acts as an intermediary mechanism between the encoder and decoder, decoupling the timing of scaling factor signaling from its usage. The buffer mediates the temporal discrepancy by holding scaling factors until they are needed for filtering operations in appropriate temporal layers, simplifying the overall system coordination

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If temporal layers are selectively received to reduce bandwidth usage, then transmission efficiency is improved, but adaptive loop filtering reliability deteriorates due to missing scaling factors

Engineering Contradiction:

Improvebandwidth efficiencyVSAvoidfiltering reliability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent resolves the contradiction by transitioning from a single temporal dimension to a two-dimensional solution: temporal layer selection for bandwidth efficiency, combined with a buffer dimension that stores scaling factors across all temporal layers. This allows receivers to selectively decode only needed temporal layers while the buffer ensures scaling factors are available whenever needed for filtering

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The buffer provides beforehand cushioning by pre-storing scaling factors for all temporal layers, including those that may not be received. This cushioning effect ensures that even if temporal layer N is not received, the scaling factor is already buffered and available for use in temporal layers N-1 and earlier, maintaining filtering reliability

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Data Source

PatentUS20250392710A1Temporal scalability for adaptive loop filter scaling factors for video coding

Publication Date: 2025.12.25 QUALCOMM INC

AI summary

A video encoder and video decoder are configured to determine a filter from a first temporal layer having a first temporal layer ID, determine a scaling factor for the filter from a second temporal layer having a second temporal layer ID, and store the scaling factor in a buffer for future usage based on the second temporal layer ID being less than or equal to the first temporal layer ID.