Encoder-Side Biased Search Ranges for Screen Capture Intra Copy
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing video codec standards, particularly HEVC, face inefficiencies in block size options and encoder decisions for intra block copy prediction, leading to suboptimal performance in scenarios involving screen capture content.
Innovation Solution
Innovations include asymmetric and symmetric partitioning of blocks for intra block copy prediction, using bottom-up and iterative evaluation methods for block vector estimation, and employing search ranges with horizontal or vertical bias during encoding and decoding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional symmetric block partitioning is used for intra BC prediction, then the encoding process is simple, but the rate-distortion performance is suboptimal for screen capture content
Solution Approach 1:
The patent introduces asymmetric block partitioning modes that divide a current block into partitions of different sizes (e.g., 2N×N and 2N×2N, or N×2N and 2N×2N) instead of traditional symmetric divisions. This asymmetry allows better adaptation to the directional characteristics of screen capture content, improving rate-distortion performance by more accurately modeling the actual content structure.
Solution Approach 2:
The patent segments the block vector search process into multiple stages: first evaluating smaller partition sizes (N×N, 2N×N), then progressively evaluating larger partitions (2N×2N, 4N×4N). This segmented approach systematically explores the solution space while maintaining manageable complexity through iterative refinement.
2Manufacturing precision
If limited block size options are used in intra BC prediction, then the encoder complexity is reduced, but the prediction accuracy deteriorates
Solution Approach 1:
The patent implements dynamic block size selection where the encoder adaptively chooses from multiple partition sizes (N×N, 2N×N, 2N×2N, 4N×4N) based on the actual content characteristics. This dynamic approach allows the system to increase prediction accuracy when needed while avoiding unnecessary complexity for simpler content, resolving the trade-off between accuracy and encoder complexity.
Solution Approach 2:
The patent changes the parameter of block size from a fixed limited set to a variable multi-size system. By allowing block sizes to vary dynamically based on content analysis, the system achieves higher prediction accuracy for diverse screen capture content while the encoder complexity increases only moderately due to systematic evaluation procedures.
3Manufacturing precision
If exhaustive block vector search is performed, then the prediction quality is maximized, but the encoding time increases significantly
Solution Approach 1:
The patent employs periodic evaluation where blocks are processed in cycles of increasing size: first all N×N partitions are evaluated, then 2N×N and 2N×2N partitions, and finally 4N×4N partitions. This periodic, staged approach ensures thorough search for high prediction quality while controlling encoding time by systematically limiting the search depth and allowing early termination when satisfactory matches are found.
Solution Approach 2:
The patent performs preliminary evaluation of smaller block partitions before committing to larger, more computationally intensive searches. By first assessing N×N and 2N×2N partitions, the encoder can identify promising candidates early and limit subsequent exhaustive search to only those regions, thereby maintaining high prediction quality while significantly reducing overall encoding time.
Data Source
AI summary
Innovations in encoder-side search ranges having horizontal bias or vertical bias are described herein. For example, a video encoder determines a block vector (“BV”) for a current block of a picture, performs intra prediction for the current block using the BV, and encodes the BV. The BV indicates a displacement to a region within the picture. When determining the BV, the encoder checks a constraint that the region is within a BV search range having a horizontal bias or vertical bias. The encoder can select the BV search range from among multiple available BV search ranges, e.g., depending at least in part on BV values of one or more previous blocks, which can be tracked in a histogram data structure.