Intra-Block Copy Template Matching for Finer Block Vector Precision
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Solution Overview
Problem
Existing video coding methods, particularly in intra prediction, face limitations in efficiently exploiting spatial and temporal redundancy in video content, leading to suboptimal compression efficiency.
Innovation Solution
Implementing a method that enhances intra prediction by using template matching to refine block vectors in intra-block copy (IBC) processes, allowing for finer precision without additional signaling, by searching for the best match of L-shaped neighboring pixels within reconstructed blocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If template matching with finer precision is implemented in intra-block copy processes, then video compression efficiency is improved, but computational complexity and processing time increase
Solution Approach 1:
The template matching process is divided into multiple precision levels (e.g., integer-pixel precision followed by sub-pixel precision refinement). The search space is segmented into coarser and finer grids, allowing the algorithm to first identify approximate matches at lower complexity, then refine only promising candidates at higher precision, thus reducing overall computational burden while maintaining compression efficiency.
Solution Approach 2:
Instead of performing full-precision template matching across the entire search space, the method applies finer precision only to selected template candidates that show promise at coarser precision levels. This partial application of high-precision processing reduces computational complexity while still achieving the compression efficiency benefits where they matter most.
2Measurement precision
If additional signaling is used to indicate finer precision block vectors, then encoding accuracy is improved, but bitrate increases
Solution Approach 1:
The patent applies finer precision block vector signaling only when template matching actually achieves improvement over conventional methods. For blocks where coarse precision suffices, additional precision signaling is omitted. This selective approach ensures that bitrate is consumed only when it provides measurable encoding accuracy benefits.
Solution Approach 2:
The method dynamically adjusts the precision parameter of block vectors based on the actual matching results and block characteristics. Rather than uniformly using high precision for all blocks, the system changes the precision parameter adaptively, using finer precision only when the template matching process identifies significant improvements, thereby optimizing the trade-off between accuracy and bitrate.
3Measurement precision
If template matching is performed across the entire reconstructed block, then matching accuracy is improved, but processing time increases
Solution Approach 1:
The search space within reconstructed blocks is segmented into multiple precision levels and candidate regions. Instead of uniformly searching all locations at full precision, the method segments the search into a coarse initial pass that identifies candidate regions, followed by a refined search at higher precision only within those candidate regions, significantly reducing processing time while maintaining matching accuracy.
Solution Approach 2:
A preliminary coarse-precision template matching is performed across the entire reconstructed block to identify promising candidate locations before conducting the computationally intensive fine-precision search. This preliminary action filters out non-promising regions, allowing the high-accuracy search to be concentrated only where it is likely to succeed, thus reducing overall processing time.
Data Source
AI summary
In a video coding system, it is proposed to improve the intra prediction based on intra-block copy by allowing a decoder-side refinement allowing further refinement of the block vector obtained from IBC using a template matching process. In this template matching, the decoder searches in an iterative process the best match for the current block (L-shaped) template within the reconstructed area, adjacent to the block vector determined using the IBC 10 prediction. This technique allows to obtain a finer precision that what is possible with IBC while minimizing the amount of coding information. In at least one embodiment where a coarse precision is used for IBC, it allows at the same time to benefit from significant coding gain provided by IBC while providing a much finer precision with reduced signaling of the block vector.