Bi-Prediction Merge BCW Index Selection Using Template Matching

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Solution Overview

Problem

The inherited BCW index for merge-coded blocks in the VVC and ECM specifications may not be suitable, leading to inefficiencies in bi-prediction processes.

Innovation Solution

Derivation of a merge candidate BCW index based on template matching cost, utilizing a set of possible weight values to optimize the bi-prediction process.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If the BCW index is inherited from neighboring blocks according to the VVC and ECM specifications, then the decoding process is simplified and processing speed is improved, but the accuracy and suitability of the BCW index for the current merge-coded block deteriorates

Engineering Contradiction:

Improveprocessing speedVSAvoidBCW index accuracy

Core Design Contradiction:

SpeedVSMeasurement precision

Solution Approach 1:

The patent replaces the simple inheritance mechanism (copying BCW index from neighboring blocks) with a template matching mechanism that calculates similarity metrics. This substitution allows the system to select the most suitable BCW index based on actual block content similarity rather than positional proximity, resolving the contradiction between processing simplicity and index accuracy.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces a feedback mechanism where the template matching cost is calculated and used to select the optimal BCW index from multiple candidates. The system evaluates the matching cost for different BCW indices and selects the one with the minimum cost, creating a closed-loop optimization that improves accuracy while maintaining reasonable processing efficiency.

Inventive Principle:

Principle #23Feedback

2Measurement precision

If template matching cost is used to derive the merge candidate BCW index, then the accuracy and suitability of the BCW index is improved, but the computational complexity and processing time increases

Engineering Contradiction:

ImproveBCW index accuracyVSAvoidcomputational complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent applies partial action by limiting the template matching process to specific candidate blocks and using a simplified matching cost calculation. Rather than performing exhaustive template matching on all possible blocks with full complexity, the method selectively applies template matching to merge candidate blocks and uses a streamlined cost function, achieving improved accuracy with reduced computational burden.

Inventive Principle:

Principle #16Partial or excessive action

Solution Approach 2:

The patent changes the parameter of BCW index selection from a simple inheritance rule to a template matching-based selection. This parameter change transforms the selection criterion from positional (inherited from neighbors) to content-based (selected by matching cost), thereby improving accuracy while the selective application to only merge-coded blocks controls the increase in complexity.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If the inherited BCW index is used for merge-coded blocks, then the coding process is faster and more efficient, but the coding performance and prediction accuracy deteriorates

Engineering Contradiction:

Improvecoding efficiencyVSAvoidprediction accuracy

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent performs preliminary template matching and BCW index selection specifically for merge-coded blocks before final encoding. By pre-calculating the template matching cost and selecting the optimal BCW index in advance, the system ensures high prediction accuracy for these blocks without significantly impacting overall coding efficiency, as the additional computation is localized to specific block types.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent applies local quality by treating merge-coded blocks differently from other blocks. Instead of uniformly applying the simple inheritance rule to all blocks, the method selectively applies template matching only to merge-coded blocks where it is most beneficial, thereby improving prediction accuracy for critical blocks while maintaining high coding efficiency for the overall video stream.

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS12489886B2Deriving bi-prediction with coding unit-level weight indices for merge candidates

Publication Date: 2025.12.02 ALIBABA (CHINA) CO LTD

AI summary

A VVC-standard encoder and a VVC-standard decoder are provided, implementing derivation of a BCW index according to cost values based on template matching. A template matching cost can be calculated for each among a set of possible BCW weight values, and a BCW weight value yielding a lowest template matching cost among each template matching cost calculated can be selected as a BCW index for a bi-predicted merge candidate. Alternatively, a template matching cost can be calculated for each among a subset of possible BCW weight values based on an inherited BCW weight. Additionally, a merge candidate BCW index can be derived while adjusting template matching cost of an inherited BCW weight from a value calculated according to the VVC standard and ECM specifications, or while adjusting template matching cost of a BCW weight having equal weight from a value calculated according to the VVC standard and ECM specifications.