Intra Block Copy Video Coding with Adaptive Transform Unit Splitting
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Solution Overview
Problem
Current video coding technologies face challenges in efficiently compressing digital video due to the increasing bandwidth demand, particularly in handling large video blocks and optimizing the use of intra block copy (IBC) tools.
Innovation Solution
The proposed method involves determining whether to split a current block in a video into multiple transform units based on its characteristics, and whether to enable the intra block copy (IBC) tool, without signaling these decisions in the coded representation. This approach allows for more efficient conversion and prediction using filtered reconstructed reference samples.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the current block is split into multiple transform units, then the conversion efficiency is improved, but the signaling complexity increases
Solution Approach 1:
The current block is divided into multiple transform units (TUs) of different sizes (e.g., 32x32, 16x16, 8x8) to improve conversion efficiency. The encoder selectively applies TU splitting based on block characteristics, allowing flexible segmentation without requiring explicit signaling for each split decision, thus resolving the contradiction between improved conversion efficiency and reduced signaling complexity
Solution Approach 2:
The transform unit splitting structure is made dynamic and adaptive based on the characteristics of the current block. The encoder determines the optimal TU configuration adaptively without predetermined fixed patterns, allowing the system to optimize conversion efficiency for different block types while avoiding complex signaling through implicit or omitted signaling mechanisms
2Measurement precision
If the intra block copy tool is enabled, then the prediction accuracy is improved, but the bandwidth consumption increases
Solution Approach 1:
The intra block copy (IBC) tool copies reference blocks from previously decoded regions within the same picture to predict current blocks. This copying mechanism improves prediction accuracy by utilizing spatial redundancy within the picture, while the copied data is already available in the decoded picture buffer, avoiding additional bandwidth consumption for transmitting prediction data
Solution Approach 2:
The IBC tool serves multiple functions: it improves prediction accuracy for various block types (luma and chroma), works with different transform unit configurations, and can be applied selectively based on content characteristics. This multi-functionality allows the system to achieve high prediction accuracy without proportionally increasing bandwidth consumption, as the same IBC mechanism serves diverse coding scenarios
3Productivity
If the block size is increased, then the coding efficiency is improved, but the processing complexity increases
Solution Approach 1:
Large current blocks are segmented into multiple transform units of appropriate sizes (32x32, 16x16, 8x8) to maintain coding efficiency while managing processing complexity. The segmentation allows the encoder to process blocks in manageable units while still benefiting from the overall large block structure, balancing coding efficiency and processing complexity through hierarchical decomposition
Solution Approach 2:
Different transform unit sizes are applied to different regions within the current block based on local characteristics. Larger TUs are used in regions with smooth content where high coding efficiency is achieved, while smaller TUs are used in regions with detailed content where lower processing complexity is needed. This local adaptation optimizes the balance between coding efficiency and processing complexity across the entire block
Data Source
AI summary
A method of video processing includes determining, for a conversion between a current block of a video and a coded representation of the video, whether a syntax element indicating usage of a skip mode for an intra-block copy (IBC) coding model is included in the coded representation according to a rule that specifies that signaling of the syntax element is based on a dimension of the current block and/or a maximum allowed dimension for a block that is coded using the IBC coding model. The method also includes performing the conversion based on the determining.