Encoder-Side Biased Search Ranges for Block Vector Estimation
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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 iterative evaluation methods for block vector estimation, and biased search ranges during motion estimation to improve encoding efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If encoder uses limited block sizes for intra BC prediction 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 and second sub-blocks) that can be independently predicted using intra BC prediction with different block vectors. This segmentation allows the encoder to handle complex block structures while maintaining manageable complexity for each sub-block, thereby improving overall encoding efficiency without excessively increasing device complexity.
Solution Approach 2:
The patent introduces dynamic block size selection and adaptive partitioning strategies where the encoder can choose between different block sizes and partitioning modes based on the content characteristics. This dynamic approach allows the system to adapt to different scenarios, improving encoding efficiency while keeping the base device complexity relatively low through selective application of complex modes.
2Device complexity
If encoder uses symmetric partitioning for current block, then device complexity is reduced, but manufacturing precision of prediction deteriorates
Solution Approach 1:
The patent explicitly introduces asymmetric partitioning modes where the current block can be divided into sub-blocks of different sizes (e.g., one sub-block larger than the other). This asymmetric division allows for more precise adaptation to the actual content structure, improving prediction accuracy by matching the partitioning to the underlying image features rather than forcing symmetric divisions.
Solution Approach 2:
Different sub-blocks can have different prediction parameters, block vectors, and partitioning strategies applied locally based on their specific content characteristics. This local quality approach allows each region to be predicted with optimal parameters for its specific features, improving overall prediction accuracy without requiring complex global optimization.
3Device complexity
If encoder uses unbiased search range for block vector estimation, then device complexity is reduced, but measurement precision of block vector deteriorates
Solution Approach 1:
The search range for block vector estimation is made adaptive and content-dependent, with different search ranges and biases applied to different blocks or regions based on their characteristics. This local quality approach allows the encoder to use more precise, biased search ranges for blocks that benefit from them while maintaining simpler, unbiased searches for blocks where such complexity is unnecessary, thereby improving overall measurement precision without uniformly increasing device complexity.
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.