Block-Based Adaptive Loop Filtering with Luma–Chroma APS Signaling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing video coding technologies lack flexibility in applying adaptive loop filters (ALF) parameters for different color components, leading to suboptimal coding efficiency.
Innovation Solution
Implementing techniques that allow signaling a number of adaptive parameter sets and indices for both luma and chroma blocks within a picture, slice, or tile group, enabling more flexible application of ALF parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single adaptive parameter set is used for all blocks in a picture/slice/tile, then device complexity is reduced, but adaptability and coding efficiency deteriorate
Solution Approach 1:
The picture/slice/tile is divided into multiple adaptive parameter sets (APS), each containing ALF parameters for specific blocks. The encoder signals multiple APS indices (e.g., apsIdxLuma, apsIdxChroma) that reference different parameter sets, allowing different regions to use different filtering parameters. This segmentation enables region-specific optimization while managing complexity through indexed reference.
Solution Approach 2:
Different ALF parameters are applied to different spatial regions (luma blocks, chroma blocks) based on their specific characteristics. Each APS contains parameters optimized for local content properties, allowing the filtering to adapt to local image features rather than applying uniform parameters globally. This improves coding efficiency by matching parameters to local requirements.
2Productivity
If separate adaptive parameter sets are used for luma and chroma blocks, then coding efficiency is improved, but device complexity increases
Solution Approach 1:
The adaptive parameter sets are segmented into separate sets for luma components and chroma components. The encoder independently manages apsIdxLuma for luma blocks and apsIdxChroma for chroma blocks, allowing different parameter optimizations for each color component type. This separation enables component-specific tuning that improves overall coding efficiency.
Solution Approach 2:
The adaptive parameter set structure is designed to be universally applicable to both luma and chroma blocks through a common APS framework. The same APS indexing mechanism and parameter structure can be used for different color components, providing a unified solution that handles multiple functions (luma filtering, chroma filtering) through a single versatile system.
Data Source
Figure 1
Figure 2
Figure 3A~3D
AI summary
A method of decoding video data including decoding, from a video bitstream for which adaptive loop filtering is enabled for luma blocks of one or more of a picture, a slice, a tile, or a tile group, a first syntax element indicating a number of adaptive parameter sets for the luma blocks, decoding a plurality of first adaptive parameter set indices for the luma blocks based on the number of adaptive parameter sets for the luma blocks, and decoding, from the video bitstream for which adaptive loop filtering is enabled for chroma blocks of the one or more of the picture, the slice, the tile, or the tile group, a second adaptive parameter set index for the chroma blocks.