Virtual Buffer Mapping for Intra-Block Copy Video Coding

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Solution Overview

Problem

Current video coding standards face challenges in efficiently managing virtual buffers for intra block copy (IBC) operations, particularly when CTU sizes exceed 128x128, and there is a lack of clarity on the relationship between virtual buffer size and reference sample size, leading to restricted subpicture areas and potential chroma QP table misdesign.

Innovation Solution

The implementation of general virtual buffers for IBC, where the size of the virtual buffer is determined by the virtual pipeline data unit (VPDU) size, CTB/CTU size, and specific constraints are applied to ensure that reference blocks are fully within VPDU rows or columns, with additional operations required to fill prediction values when blocks cross multiple VPDUs, and block vectors are constrained within specific ranges.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the virtual buffer size is increased to support larger CTU sizes (greater than 128x128), then the IBC operation capability is improved, but the memory usage and buffer management complexity increase

Engineering Contradiction:

ImproveIBC operation capabilityVSAvoidbuffer management complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The virtual buffer is divided into multiple sub-picture areas, each independently managed. This segmentation allows the system to handle large CTU sizes by processing smaller, manageable sub-regions, reducing the complexity of buffer management while maintaining support for large block copy operations

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The buffer management system dynamically adjusts the virtual buffer size and subpicture area boundaries based on the actual CTU size and IBC operation requirements. This dynamic adaptation allows the system to optimize memory usage for different picture sizes and coding scenarios

Inventive Principle:

Principle #15Dynamics

2Ease of operation

If the reference block must be fully within VPDU rows or columns, then the buffer management becomes simpler, but the flexibility in IBC operations is reduced

Engineering Contradiction:

Improvebuffer management easeVSAvoidIBC operation flexibility

Core Design Contradiction:

Ease of operationVSAdaptability or versatility

Solution Approach 1:

The patent introduces a virtual buffer coordinate system that maps logical reference block positions to physical buffer locations. This dimensional transformation allows reference blocks to logically span across VPDU boundaries while physically being managed within constrained regions, maintaining both simplicity and flexibility

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Manufacturing precision

If additional operations are performed to fill prediction values when blocks cross multiple VPDUs, then the prediction accuracy is improved, but the computational complexity increases

Engineering Contradiction:

Improveprediction accuracyVSAvoidcomputational complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The system pre-calculates and stores prediction values in the virtual buffer before actual IBC operations are performed. When blocks cross VPDU boundaries, these pre-computed values are readily available, avoiding complex real-time calculations and reducing computational complexity while maintaining prediction accuracy

Inventive Principle:

Principle #10Preliminary action

4Quantity of substance

If the virtual buffer size is determined by VPDU size and CTB/CTU size, then the memory usage efficiency is improved, but the adaptability to different picture configurations is reduced

Engineering Contradiction:

Improvememory usage efficiencyVSAvoidpicture configuration adaptability

Core Design Contradiction:

Quantity of substanceVSAdaptability or versatility

Solution Approach 1:

The virtual buffer dimensions are defined as functions of VPDU size and CTB/CTU size parameters, allowing the buffer configuration to automatically adapt to different picture resolutions and coding tree block sizes. This parameter-based approach maintains memory efficiency while providing flexibility across various picture configurations

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS11533507B2Mapping restriction for intra-block copy virtual buffer

Publication Date: 2022.12.20 DOUYIN VISION CO LTD

AI summary

A method for video processing includes determining, for a conversion between a current video block of a video picture of a video and a bitstream of the video, a number of reference samples in a virtual buffer comprising reference samples derived from the video picture based on a rule, wherein the rule specifies that a maximum number of available reference samples in the virtual buffer is less than a size of the virtual buffer; and performing the conversion based on the determining, wherein the current video block is coded in a prediction mode in which prediction samples are derived from blocks of the available reference samples in the virtual buffer based on a block vector.