Motion Vector Difference Scaling in Video Coding

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Solution Overview

Problem

Current video coding standards, such as ITU-T H.264 and H.265, face challenges in efficiently deriving motion vector differences, particularly when inter-layer prediction is used, leading to suboptimal scaling factors that do not effectively account for the distance between reference pictures and the current picture.

Innovation Solution

The proposed method determines whether inter-layer prediction is utilized by checking the usage of reference pictures in different lists and sets a scaling factor to 1 when inter-layer prediction is used, or a value between -4096 and 4095 when it is not, to derive the motion vector difference based on this determination.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a fixed scaling factor is used for motion vector difference derivation, then the derivation process is simple, but it does not effectively account for the distance between reference pictures and the current picture

Engineering Contradiction:

Improvesimplicity of derivation processVSAvoidaccuracy of motion vector difference

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The patent applies dynamics by making the scaling factor variable rather than fixed. The scaling factor is dynamically adjusted based on the picture order count difference between reference pictures and the current picture, allowing the system to adapt to different temporal distances and improve motion vector difference accuracy accordingly.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the parameter of the scaling factor from a constant value to a variable that depends on the picture order count difference. This parameter change enables the system to account for the distance between reference pictures and the current picture, thereby improving the accuracy of motion vector difference derivation.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If different scaling factors are used for inter-layer prediction and non-inter-layer prediction, then the accuracy is improved, but the complexity of determining the scaling factor increases

Engineering Contradiction:

Improveaccuracy of motion vector differenceVSAvoidcomplexity of scaling factor determination

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent applies preliminary action by pre-defining the conditions for selecting different scaling factors based on the inter-layer prediction flag and picture order count differences. This allows the decoder to determine the appropriate scaling factor through straightforward conditional logic rather than complex calculations, reducing computational complexity while maintaining accuracy.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS11516476B2Systems and methods for deriving a motion vector difference in video coding

Publication Date: 2022.11.29 SHARP KK

AI summary

A method of deriving a motion vector difference for coding video data, the method comprises determining whether inter-layer prediction is utilized by determining whether both a reference picture in a first reference picture list is not marked as used for long-term reference and a reference picture in a second reference picture list is not marked as used for long-term reference; based on whether the inter-layer prediction is utilized, setting a scaling factor to one of: a value of 1 in a case where the inter-layer prediction is utilized; or a value in the range of −4096 to 4095 in a case where the inter-layer prediction is not utilized; and deriving the motion vector difference based on the scaling factor.