Block Vector Prediction for Efficient Intra-Block Copy Coding

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Solution Overview

Problem

The HEVC standard's intra block copy (BC) prediction mode inefficiently signals block vector (BV) values and fails to effectively handle blocks with predictable displacements, leading to suboptimal coding efficiency.

Innovation Solution

Implementing a default BV predictor with a non-zero value, using skip mode for BV prediction, and employing merge mode to select among multiple BV predictor candidates, thereby improving coding efficiency for intra-BC-predicted blocks.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of information

If intra block copy prediction mode is used with conventional BV signaling, then block displacement prediction can be performed, but BV values are not signaled efficiently and coding efficiency is suboptimal

Engineering Contradiction:

ImproveBV signaling efficiencyVSAvoidcoding efficiency

Core Design Contradiction:

Loss of informationVSProductivity

Solution Approach 1:

The patent applies preliminary action by establishing default BV predictor candidates before actual BV signaling. These default candidates (e.g., vertical, horizontal, and diagonal predictors) are pre-defined based on the current block's position and neighboring blocks, allowing the encoder to signal only deviations from these defaults rather than complete BV values, thus improving signaling efficiency

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the parameter representation by transitioning from signaling absolute BV values to signaling differential values relative to default predictors. This parameter transformation allows more efficient entropy coding, especially when BV values follow predictable patterns such as vertical or horizontal displacements common in screen-capture content

Inventive Principle:

Principle #35Parameter changes

2Reliability

If conventional BV signaling is used, then block prediction can be performed, but blocks with predictable BC displacement are not efficiently handled

Engineering Contradiction:

Improveprediction accuracyVSAvoidbit rate efficiency

Core Design Contradiction:

ReliabilityVSLoss of information

Solution Approach 1:

The patent applies local quality by providing different default BV predictor candidates based on the specific characteristics and position of each current block. Different default predictors (vertical, horizontal, diagonal) are selected according to the local pattern characteristics, allowing the system to adapt to local displacement patterns rather than using a uniform signaling approach

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent uses preliminary action by pre-defining multiple default BV predictor candidates that capture common displacement patterns. These predictors are established before encoding, enabling the system to efficiently handle predictable displacements by signaling only when and how the actual BV deviates from these pre-planned candidates

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS20250227286A1Block vector prediction in video and image coding/decoding

Publication Date: 2025.07.10 MICROSOFT TECHNOLOGY LICENSING LLC

AI summary

Innovations in the area of prediction of block vector (“BV”) values improve encoding or decoding of blocks using intra block copy (“BC”) prediction. For example, some of the innovations relate to use of a default BV predictor with a non-zero value. Other innovations relate to use of a selected one of multiple BV predictor candidates for a current block. Still other innovations relate to use of a skip mode in which a current intra-BC-predicted block uses a predicted BV value.