Video Block Partition Rules for Color Format and IBC Constraints
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Solution Overview
Problem
Existing video coding standards face inefficiencies in handling intra block copy (IBC) for screen content due to undefined pixel values when reference blocks are outside the picture or overlap with the current block, leading to potential padding requirements and reduced coding efficiency.
Innovation Solution
Implementing solutions in video coding standards like HEVC and VVC to ensure bitstream conformance by restricting reference blocks within the reconstructed area, using palette modes for efficient representation of screen content, and incorporating advanced filtering techniques such as ALF and SAO to enhance image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If reference blocks are allowed outside the picture or overlapping with current block, then more flexible block matching is achieved, but undefined pixel values occur leading to padding requirements and reduced coding efficiency
Solution Approach 1:
The patent applies different constraints to different regions of the picture. Specifically, it defines a restricted reference area that excludes regions outside the picture and overlapping regions, while allowing reference blocks within the valid reconstructed area. This local differentiation resolves the contradiction by enabling flexible matching within allowed regions while preventing the harmful effects of undefined pixel access.
Solution Approach 2:
The patent segments the reference area into valid and invalid regions. By dividing the potential reference space into restricted reference areas (where reference blocks are allowed) and forbidden regions (outside picture or overlapping areas), the system enables flexible matching in valid zones while avoiding undefined pixel values in invalid zones, thus maintaining coding efficiency.
2Device complexity
If small chroma blocks are restricted in certain color formats, then processing complexity is reduced, but coding efficiency is lost
Solution Approach 1:
The patent applies different block size constraints based on the chroma format being used. For 4:2:0 chroma format, small chroma blocks (with area less than 64 samples) are restricted to reduce processing complexity. For 4:4:4 chroma format, small chroma blocks are allowed to maintain coding efficiency. This localized approach based on color format characteristics resolves the contradiction by adapting constraints to the specific requirements of each format.
Solution Approach 2:
The patent changes the block size parameter constraints based on the chroma format parameter. When the chroma format changes from 4:2:0 to 4:4:4, the minimum allowed block area parameter changes from 64 samples to a smaller value, enabling small blocks in high-quality formats while maintaining complexity reduction in standard formats.
3Reliability
If IBC mode is restricted for small blocks, then bitstream conformance is improved, but coding efficiency is reduced
Solution Approach 1:
The patent applies different IBC mode restrictions to different block sizes and types. For luma blocks smaller than 4x4 samples, IBC mode is restricted to ensure bitstream conformance. For chroma blocks, IBC mode is allowed under certain conditions (area >= 64 for 4:2:0 format). This localized differentiation resolves the contradiction by applying conformance requirements only where necessary while preserving efficiency where safe.
Data Source
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AI summary
A method of video processing is described. The method includes determining, for a conversion between a current video block of a video and a coded representation of the video, whether a certain partitioning scheme is allowed for the current video block according to a rule that depends on a coding mode type used for representing the current video block in the coded representation and a dimension of the current video block; and performing the conversion based on the determining.