Intra Block Copy Prediction with Flipping and Skip Mode
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Solution Overview
Problem
The H.265/HEVC standard's intra block copy (BC) prediction mode faces inefficiencies in coding blocks with predictable BC displacement and handling content with reversed patterns, particularly in terms of coding efficiency.
Innovation Solution
The implementation of block flipping and skip mode signaling, where an intra-BC-predicted block's reference region is flipped relative to its original position, and a signaled block vector (BV) differential is used without residual data, to improve coding efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If intra BC prediction mode is used with standard reference region copying, then coding complexity is reduced, but coding efficiency deteriorates for blocks with predictable BC displacement and reversed patterns
Solution Approach 1:
The prediction mode is segmented into multiple types: standard intra BC prediction, flipped intra BC prediction, and skip mode. This segmentation allows the system to select the most appropriate mode for each block, improving coding efficiency without significantly increasing overall complexity through conditional mode selection
Solution Approach 2:
The patent introduces dynamic mode selection where the encoder can adaptively choose between standard intra BC prediction, flipped intra BC prediction, and skip mode based on the characteristics of each block. This dynamic adaptation improves coding efficiency for different block types while maintaining manageable complexity through context-based decision making
2Productivity
If block flipping is added to handle reversed patterns, then coding efficiency for reversed patterns improves, but device complexity increases
Solution Approach 1:
The prediction functionality is segmented into standard mode and flipped mode, allowing the system to apply flipping operations only when needed for reversed patterns. This selective application improves efficiency for specific cases while limiting the increase in overall device complexity
Solution Approach 2:
The patent applies block flipping (inversion) to the reference region to handle reversed patterns. By inverting the reference block horizontally or vertically and comparing it with the current block, the system can efficiently encode reversed patterns that would otherwise be difficult to predict, improving coding efficiency for these specific cases
3Loss of substance
If skip mode with BV differential signaling is implemented, then bit rate is reduced for predictable blocks, but device complexity increases
Solution Approach 1:
The patent extracts and signals only the block vector differential (BV differential) for skip mode blocks, omitting the full BV signaling and residual data. This extraction of essential information reduces bit rate for predictable blocks while keeping device complexity manageable through selective signaling
Solution Approach 2:
For skip mode blocks with predictable content, the patent applies partial action by signaling only the BV differential without full residual encoding. This partial signaling approach reduces bit rate for these specific blocks while maintaining acceptable reconstruction quality, balancing bit rate reduction with controlled complexity increase
Data Source
AI summary
Innovations in the area of encoding or decoding of blocks using intra block copy (“BC”) prediction improve coding efficiency for intra-BC-predicted blocks in many situations. For example, some of the innovations relate to block flipping in which an intra-BC-predicted block is flipped relative to a reference region, which can be indicated by a block vector (“BV”) value. Other innovations relate to signaling of a skip mode in which a current intra-BC-predicted block uses a signaled BV differential but lacks residual data.