Chroma Block Coding Constraints in Video Processing
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Solution Overview
Problem
Current video coding technologies face inefficiencies in handling small chroma blocks and color subsampling formats, particularly in the Versatile Video Coding (VVC) standard, which restricts coding modes and leads to unnecessary coding efficiency losses.
Innovation Solution
The proposed solution involves relaxing constraints on small chroma block sizes and prediction modes based on chroma formats, allowing for more flexible partitioning and prediction techniques, such as enabling intra block copy (IBC) and palette modes for specific chroma formats, and adjusting signaling mechanisms to improve coding efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If constraints on small chroma block sizes are applied, then coding complexity is reduced, but coding efficiency deteriorates
Solution Approach 1:
The patent applies different constraint rules for small chroma blocks based on their specific characteristics (size, position, neighboring blocks). Instead of a uniform constraint approach, the system evaluates local conditions such as whether a chroma block is 4x4 or smaller, whether it has luma neighbors, and applies selective restrictions only where necessary to maintain coding efficiency while managing complexity.
Solution Approach 2:
The patent modifies the constraint parameters dynamically based on chroma block properties. The system changes the applicability of certain constraints (such as IBC mode restrictions or partitioning limitations) according to parameters like block size, chroma format (4:2:0, 4:2:2, 4:4:4), and spatial position, thereby optimizing the balance between complexity and efficiency.
2Ease of manufacture
If restricted coding modes are applied to small chroma blocks, then hardware implementation is simplified, but coding efficiency deteriorates
Solution Approach 1:
The patent implements dynamic mode selection where the available coding modes for a chroma block change based on its size and configuration. The system dynamically enables or disables certain modes (such as IBC, palette, or specific partitioning modes) according to whether the block is small (4x4 or smaller) and meets other criteria, allowing hardware to adapt its behavior based on the specific coding situation rather than using a fixed simplified approach.
3Device complexity
If uniform constraints are applied to all chroma formats, then rule complexity is reduced, but adaptability deteriorates
Solution Approach 1:
The patent introduces asymmetric treatment of different chroma formats (4:2:0, 4:2:2, 4:4:4) and block sizes. Instead of uniform symmetric rules, the system applies different constraint applicability based on the specific chroma format and block dimensions, allowing optimized behavior for each configuration while managing rule complexity through structured conditional logic.
Data Source
AI summary
A method of video processing is provided to include: performing a conversion between a video including one or more video regions including one or more luma blocks and one or more chroma blocks and a coded representation of the video according to a rule; wherein the rule specifies that a chroma block from the one or more chroma blocks having a size M×N is disallowed to be represented in the coded representation using an intra mode or an intra block copy mode, wherein M and N are integers that indicate a width and a height of the chroma block, respectively; wherein the intra mode includes encoding the chroma block based on previously encoded or reconstructed video blocks, and wherein the intra block copy mode includes encoding the chroma block using at least a block vector pointing to a video frame containing a video region.