Chroma Deblocking Using QP Offsets Across Coding Unit Levels
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Solution Overview
Problem
Current video coding standards face challenges in achieving optimal deblocking filtering processes, particularly in handling chroma components, which can lead to inefficiencies in compression and complexity, especially with advancements in video codecs like HEVC and VVC.
Innovation Solution
The proposed method involves selective application of deblocking filters based on chroma quantization parameter (QP) offsets and rules, independent of coding modes, and uses chroma QP offsets at different video unit levels to determine filtering parameters, enabling efficient conversions between video blocks and bitstream representations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If deblocking filtering is applied to chroma components using conventional methods, then blocking artifacts are reduced, but processing complexity and computational overhead increase
Solution Approach 1:
The patent changes the parameter used for deblocking filter decision from luma QP to chroma QP. Specifically, it uses chroma quantization parameter offsets (cb_qp_offset, cr_qp_offset) added to chroma QP table values to determine filtering parameters beta and tc. This parameter substitution allows the filter to adapt to chroma-specific characteristics while maintaining computational efficiency.
Solution Approach 2:
The patent applies local quality by treating chroma components differently from luma components in the deblocking process. Instead of using a unified QP approach, it derives separate chroma QP values by adding offsets to chroma QP table entries, allowing the filtering to be optimized for chroma-specific blockiness issues while preserving luma processing independence.
2Productivity
If chroma QP offsets are used to determine deblocking parameters, then compression efficiency is improved, but the complexity of QP management increases
Solution Approach 1:
The patent makes the chroma QP offset mechanism universal by applying the same offset-based approach to both Cb and Cr chroma components. The chroma_qp_offset_cb and chroma_qp_offset_cr parameters are used consistently across different chroma blocks and coding units, providing a unified method for chroma QP management that simplifies implementation despite handling multiple components.
Solution Approach 2:
The patent segments the QP management into distinct components: base chroma QP from the QP table, offsets for Cb component (chroma_qp_offset_cb), offsets for Cr component (chroma_qp_offset_cr), and additional offsets for specific coding units (cu_chroma_qp_offset). This segmentation allows flexible combination of QP adjustments at different hierarchical levels without creating complex interdependencies.
3Productivity
If deblocking filtering is selectively applied based on chroma QP offsets, then processing efficiency is improved, but filtering consistency across different coding modes may be affected
Solution Approach 1:
The patent introduces dynamics by making the deblocking filter application conditional rather than static. The filter is selectively applied based on computed boundary strength values that depend on chroma QP offsets and coding mode characteristics. This allows the filtering behavior to adapt dynamically to local chroma characteristics while maintaining consistent decision-making logic across different coding modes through unified boundary strength computation.
Data Source
AI summary
An example method of video processing includes determining, for a conversion between a block of a chroma component of a video and a bitstream representation of the video, whether or how to apply a filtering process to an edge of the block based on a first quantization information for a first video region including samples on one side of the edge and/or a second quantization information for a second video region including samples on the other side of the edge according to a rule that is based on a coding mode applicable to the block for coding the samples on the one side or the samples on the other side of the edge. The rule specifies that multiple QP offsets at different video unit levels are used to determine the first quantization information or the second quantization information. The method also includes performing the conversion based on the determining.