Chroma Deblocking Filter Pipelining and Luma Merging
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Solution Overview
Problem
The HEVC standard's chroma deblock filtering process results in severe color artifacts due to differing filter strengths and limited modes, leading to inadequate smoothing of blockiness artifacts in chroma components.
Innovation Solution
The proposed method performs chroma deblock filtering in a pipelined fashion, allowing for deblocking of each sample as it is received, without needing to know the boundary strengths and coding modes of adjacent samples, and applies filtering techniques similar to those used for luma components to improve chroma deblocking efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If chroma deblock filtering is applied with limited modes and differing filter strengths as per HEVC standard, then processing complexity is reduced, but color artifacts and blockiness appear in chroma components
Solution Approach 1:
The patent merges luma and chroma deblock filtering processes by applying the same filtering operations to both components. The filter uses identical boundary strength calculations and filtering coefficients for both luma and chroma samples, eliminating the need for separate filtering modes and reducing color artifacts caused by differential filtering.
Solution Approach 2:
The patent creates a universal deblock filtering mechanism that handles both luma and chroma components using the same filter structure, boundary strength determination, and filtering coefficients. This multi-functional approach replaces the HEVC standard's separate filtering paths, reducing complexity while maintaining quality for both component types.
2Productivity
If chroma deblock filtering is applied only at 16×16 boundaries in 4:2:0 sampling structure, then processing load is reduced, but blockiness artifacts remain visible in chroma samples
Solution Approach 1:
The patent segments the filtering approach by applying different filtering operations to different boundary types. It performs strong filtering at 4×4 boundaries within LCUs and conditional filtering at LCU boundaries, rather than applying a single filtering mode at all boundaries. This segmented approach reduces processing load while effectively removing blockiness artifacts at critical locations.
3Device complexity
If deblock filtering is applied only when adjacent coding units use intra mode prediction, then processing complexity is reduced, but filtering is insufficient for inter-mode blocks causing color artifacts
Solution Approach 1:
The patent implements dynamic boundary strength calculation that adapts to different prediction modes. Instead of applying filtering only to intra-mode blocks, the filter calculates boundary strength based on gradient values and variance for both intra and inter modes. This dynamic approach ensures appropriate filtering is applied to inter-mode blocks when needed, reducing color artifacts without unnecessarily increasing complexity for all blocks.
Data Source
AI summary
Chroma deblock filtering of reconstructed video samples may be performed to remove blockiness artifacts and reduce color artifacts without over-smoothing. In a first method, chroma deblocking may be performed for boundary samples of a smallest transform size, regardless of partitions and coding modes. In a second method, chroma deblocking may be performed when a boundary strength is greater than 0. In a third method, chroma deblocking may be performed regardless of boundary strengths. In a fourth method, the type of chroma deblocking to be performed may be signaled in a slice header by a flag. Furthermore, luma deblock filtering techniques may be applied to chroma deblock filtering.