Hash-Based Intra-Block Copy Search for Screen Content
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing video compression methods fail to effectively compress screen content, leading to low compression performance and quality issues such as blurred curves and texts, due to their inability to accommodate the unique characteristics of screen content like sharp edges and multiple colors.
Innovation Solution
The method involves a video encoder that determines a hash value for an input video block, identifies candidate blocks within a spatial range, and selects a predictor block based on correlation between luma and chroma components to encode the input block using intra-block copy prediction, specifically using hash-based search to reduce complexity and improve prediction accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional video compression methods are used to encode screen content, then the compression process can be performed, but the compression performance is low and quality issues occur such as blurred curves and texts
Solution Approach 1:
The patent changes the approach from conventional compression parameters to hash-based block identification parameters. By computing hash values of current and candidate blocks and comparing them, the system identifies matching blocks more accurately, preserving sharp edges and text while maintaining compression efficiency. This parameter change enables better reconstruction quality without sacrificing compression performance.
2Productivity
If hash-based search is used to identify candidate blocks, then the search complexity is reduced and prediction accuracy is improved, but additional computational steps are required
Solution Approach 1:
The patent replaces the mechanical block-by-block comparison system with a hash-based identification system. Instead of directly comparing pixel data between current and candidate blocks, the system computes hash values as a substitution mechanism. This reduces the computational complexity of block matching while improving search efficiency, as hash value comparison is much faster than full block comparison.
3Loss of energy
If intra-block copy prediction is used to encode screen content blocks, then compression efficiency is enhanced and bandwidth requirements are reduced, but the method requires accurate identification of predictor blocks
Solution Approach 1:
The patent implements a feedback mechanism where hash values of candidate blocks are computed and compared with the current block's hash value. This feedback loop allows the system to iteratively identify the best predictor block by checking hash matches and refining the selection. The feedback ensures accurate predictor block identification, which is critical for achieving compression efficiency while maintaining reconstruction quality.
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
In an intra-block copy video encoding method, an encoder performs a hash-based search to identify a selected set of candidate blocks for prediction of an input video block. For each of the candidate blocks in the selected set, the encoder determines a correlation between, on the one hand, luma and chroma components of the input video block and, on the other hand, luma and chroma components of the respective candidate blocks. A predictor block is selected based on the correlation and is used to encode the input video block. In different embodiments, the correlation may be the negative of the sum of absolute differences of the components, may include a Jaccard similarity measure between respective pixels, or may be based on a Hamming distance between two high precision hash values of the input video block and the candidate block.