Intra Block Copy Video Coding Reducing Prediction Error
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Solution Overview
Problem
Current video coding standards, such as HEVC, face inefficiencies in predicting graphics and text regions within mixed content videos, leading to higher prediction error levels and reduced coding efficiency.
Innovation Solution
The implementation of an intra block copy (IntraBC) technique, which restricts the search area for predicting blocks of pixels to the reconstructed portion of the largest coding unit (LCU) and its left neighboring LCUs, using one-dimensional or two-dimensional searches to find the best matching block, thereby reducing complexity and memory requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If motion compensated prediction or intra prediction is used for screen content video, then coding efficiency is improved for natural video, but prediction error levels increase for graphics and text regions
Solution Approach 1:
The patent applies copying by directly copying pixel blocks from previously decoded regions within the same picture to predict current blocks. This intra-picture block copying approach is particularly effective for screen content video with graphics and text, as it replicates exact pixel patterns rather than using motion compensation or gradient-based intra prediction, thereby eliminating prediction errors for repetitive patterns.
Solution Approach 2:
The patent segments the prediction process by introducing a separate intra-block copy mode distinct from traditional motion compensation and intra prediction. The picture is divided into blocks that can be independently predicted using block copying from spatially nearby regions, allowing different prediction strategies to be applied to different content types within the same picture.
2Measurement precision
If a large search area is used for block matching, then prediction accuracy is improved, but computational complexity and memory requirements increase
Solution Approach 1:
The patent applies local quality by restricting the block copying search to local spatial regions within the same picture, specifically to blocks that have already been decoded and reconstructed. Rather than searching the entire picture or using complex motion vector searches, the method focuses on locally available reconstructed blocks, reducing search complexity while maintaining effectiveness for screen content.
Solution Approach 2:
The patent uses partial action by performing block matching only within a limited search space of already-decoded blocks rather than exhaustively searching the entire picture. This partial search approach is sufficient for screen content video where redundant patterns typically appear in spatially nearby regions, avoiding the excessive computational cost of full-picture searches.
Data Source
AI summary
A method for decoding encoded blocks of pixels from an encoded video bit stream is provided that includes decoding a block vector corresponding to an encoded block of pixels from the encoded bit stream, verifying that the block vector indicates a block of reconstructed pixels in a search area including reconstructed pixels of a largest coding unit (LCU) including the encoded block of pixels and N left neighboring reconstructed LCUs of the LCU, and decoding the encoded block of pixels, wherein the block of reconstructed pixels is used as a predictor for the encoded block of pixels.