Biased Block Vector Search Ranges for Intra Block Copy Encoding
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Solution Overview
Problem
Existing video codec standards, particularly HEVC, face limitations in block sizes for intra block copy prediction and inefficient encoder decisions, leading to suboptimal encoding efficiency.
Innovation Solution
Innovations in intra block copy prediction include asymmetric and symmetric partitioning of blocks, bottom-up and top-down approaches for partitioning, and biased block vector search ranges to enhance encoding efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If intra BC prediction uses limited block sizes as specified in HEVC standard, then device complexity is reduced, but encoding efficiency deteriorates
Solution Approach 1:
The current block is divided into multiple sub-blocks (first sub-block and second sub-block) with different sizes. The encoder selectively applies intra BC prediction to specific sub-blocks based on their characteristics, allowing flexible adaptation to different content types while maintaining manageable complexity through structured segmentation.
Solution Approach 2:
The patent introduces dynamic block size selection where the encoder can choose between different block sizes (e.g., 2N×2N, 2N×N, N×2N) and partitioning schemes (horizontal, vertical, asymmetric) based on the specific picture content and predicted block vector directions, making the encoding process adaptive rather than static.
2Measurement precision
If encoder uses exhaustive search for block vector estimation, then prediction accuracy is improved, but computational complexity increases
Solution Approach 1:
The patent applies different search strategies to different sub-blocks based on their local characteristics. For example, sub-blocks with horizontal motion patterns use horizontal search ranges, while those with vertical patterns use vertical search ranges. This localized approach improves accuracy for each region without requiring exhaustive search across the entire block.
Solution Approach 2:
Instead of performing exhaustive search over the complete search range for all blocks, the encoder performs partial search by limiting the search to biased ranges (horizontal or vertical) based on predicted motion directions. This partial action achieves sufficient accuracy for most cases while significantly reducing computational complexity.
3Adaptability or versatility
If encoder uses asymmetric partitioning for intra BC prediction, then adaptability to different motion patterns is improved, but device complexity increases
Solution Approach 1:
The patent introduces asymmetric partitioning where the current block is divided into sub-blocks of different sizes (e.g., one 2N×N sub-block and one N×2N sub-block) rather than equal partitions. This asymmetric structure better matches real-world motion patterns where different regions of a block often move in different directions and magnitudes, improving prediction accuracy.
Solution Approach 2:
The encoder dynamically selects the partitioning scheme (horizontal, vertical, or asymmetric) based on the predicted block vector directions and content characteristics. This dynamic adaptation allows the system to optimize for different motion patterns without requiring manual configuration, achieving versatility through algorithmic decision-making.
Data Source
AI summary
Innovations in intra block copy (“BC”) prediction as well as innovations in encoder-side search patterns and approaches to partitioning are described herein. For example, some of the innovations relate to use of asymmetric partitions for intra BC prediction. Other innovations relate to search patterns or approaches that an encoder uses during block vector estimation (for intra BC prediction) or motion estimation. Still other innovations relate to uses of BV search ranges that have a horizontal or vertical bias during BV estimation.