Octree Planar Mode Contexts for Point Cloud Occupancy Coding
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Solution Overview
Problem
Current point cloud compression methods, particularly using octree-based coding, fail to efficiently exploit planarity in non-natural environments, leading to suboptimal compression performance due to the uniform partitioning process, which does not effectively utilize horizontal and vertical directionality.
Innovation Solution
Implementing a planar coding mode that signals whether a volume is planar based on occupancy patterns, allowing for inference of occupancy bits and reducing the need to encode all bits, thereby improving compression efficiency by adapting to local data characteristics and probability of planarity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If uniform octree-based partitioning is used, then the coding structure is simple and systematic, but compression performance is suboptimal because planarity in non-natural environments is not exploited
Solution Approach 1:
The patent introduces a dynamic planar coding mode that adapts to local data characteristics. Instead of using a static uniform partitioning approach throughout, the system dynamically switches between conventional octree coding and planar coding based on the detected occupancy patterns. This allows the coding structure to adapt to the inherent planarity in non-natural environments while maintaining the systematic octree structure where planarity is not present.
Solution Approach 2:
The patent applies different coding strategies to different regions of the point cloud based on local characteristics. When planarity is detected in a specific volume (through occupancy patterns indicating points lie on one or more planes), planar coding mode is activated for that local region. This allows optimal compression for planar regions while maintaining standard octree coding for non-planar regions, achieving local optimization without compromising overall structure.
2Loss of information
If all occupancy bits are encoded explicitly, then complete information is preserved, but bitstream size increases and compression efficiency decreases
Solution Approach 1:
The patent extracts and utilizes planarity information from occupancy patterns to infer the values of certain occupancy bits. When points are detected to lie on one or more planes within a volume, the system can infer occupancy status for regions that would otherwise require explicit encoding. This extraction of planarity characteristics allows the system to derive implicit information, reducing the number of bits that need to be explicitly encoded while preserving complete occupancy information.
Solution Approach 2:
The planar coding mode enables the system to self-determine occupancy bit values through planarity inference. Instead of requiring external explicit encoding for all occupancy bits, the system uses the detected planar structure to automatically infer missing occupancy information. This self-service mechanism reduces bitstream size while maintaining information completeness, as the inference process is performed autonomously based on local geometric characteristics.
Data Source
AI summary
Method and devices for coding point cloud data using a planar coding mode. The planar coding mode may be signaled using in a planar mode flag to signal that a volume is planar. A planar volume has all of its occupied child nodes on one side of a plane bisecting the volume. A planar position flag may signal which side of the volume is occupied. Entropy coding may be used to code the planar mode flag and/or the planar position flag. Context determination for coding may take into account one or more of whether a parent volume containing the volume is planar in occupancy, occupancy of a neighbouring volume at a parent depth, distance between the volume and a closest already-coded occupied volume at a same depth as the volume, plane position, if any, of the closest already-coded occupied volume, and a position of the volume within the parent volume.