Intra Block Copy Vector-Difference Wrap-Around for Video Compression
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Solution Overview
Problem
Existing video encoding and decoding systems face inefficiencies in compressing and decompressing large video sequences due to redundant information, leading to high resource requirements for storage and transmission.
Innovation Solution
Intra block copy (IBC) vector difference wrap around technique is employed to enhance video encoding and decoding by leveraging intra prediction within a single picture, reducing redundant information through intra block copying and vector difference handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If conventional video encoding is used to compress video sequences, then storage and transmission resources are consumed, but redundant information is not sufficiently reduced leading to high resource requirements
Solution Approach 1:
The patent employs intra block copy (IBC) technique where blocks within the current picture are copied to predict other blocks. This creates redundant information that needs to be transmitted, increasing bitrate. The wrap-around mode extends this copying capability to wrap around picture boundaries, further increasing redundancy but enabling better compression for certain patterns.
2Loss of substance
If intra block copy with wrap around mode is used to reduce redundant information, then encoding complexity increases due to additional boundary checking and wrap around logic
Solution Approach 1:
The patent segments the picture into multiple blocks and applies IBC technique to each block independently. The wrap-around mode divides the picture boundary checking into discrete segments (normal mode vs. wrap-around mode) that can be selectively applied. This segmentation allows the decoder to implement complexity-efficient logic by checking specific conditions rather than performing exhaustive boundary checks for all blocks.
Solution Approach 2:
The patent implements partial wrap-around mode where wrap-around behavior is applied only when beneficial (when it improves compression) rather than universally. The encoder selectively enables wrap-around mode based on content analysis, performing the additional complexity only when it provides sufficient compression benefit to justify the increased encoding and decoding effort.
3Productivity
If IBC vector difference wrap around technique is implemented, then bitrate is reduced and encoding efficiency is improved, but the quality of reconstructed video may be affected by wrap around artifacts
Solution Approach 1:
The patent changes the spatial parameters of block copying by allowing wrap-around at picture boundaries. This parameter change (from non-wraparound to wrap-around mode) enables blocks to be copied from locations that would otherwise be out of bounds, improving encoding efficiency for certain patterns. The encoder selects the appropriate mode (normal or wrap-around) based on which produces better compression for each block.
Solution Approach 2:
The patent converts the potential harm of picture boundaries (which normally restrict block copying options) into a benefit by implementing wrap-around mode. The picture boundary, instead of being a hard limit, becomes a wrap point that enables additional valid copy sources. This transforms the boundary from a constraint into an opportunity for better compression, particularly for patterns that repeat across picture edges.
Data Source
AI summary
A decoder receives, from a bitstream, an indication of a block vector predictor (BVP) and a first block vector difference (BVD) for a current block. The decoder determines a second BVD based on: the first BVD and whether a location displaced from the current block by a sum of the BVP and the first BVD is outside a reference region. The decoder calculates a block vector (BV) based on a sum of the second BVD and the BVP. The decoder reconstructs the current block based on a reference block indicated by the BV.