3D Point Cloud Color Encoding With Octree Bitrate Reduction
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Solution Overview
Problem
Existing point cloud compression methods face challenges in achieving efficient encoding and decoding of colors while balancing geometry representation and bitrate, particularly for complex geometries with high computational resources and high bitrate requirements.
Innovation Solution
An octree-based structure is used to approximate the geometry of a point cloud, with a Rate Distortion optimization process to determine the best octree-based structure, and a method for up-sampling points to reduce bitrate by encoding only specific color information, using neighboring point colors for approximation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If octree-based structure is used to approximate geometry with high precision, then geometry representation quality is improved, but bitrate and computational complexity increase
Solution Approach 1:
The point cloud is segmented into multiple octrees at different depths. Instead of using a single high-precision octree for the entire point cloud, the method divides the space into hierarchical octant structures, allowing different regions to be represented at different levels of detail. This segmentation enables precise geometry representation in important areas while using coarser approximation in less critical areas, thereby reducing overall bitrate.
Solution Approach 2:
Different regions of the point cloud are represented with different levels of precision. The method applies local quality control by allowing certain octants to be subdivided to higher depths where geometry detail is important, while other regions use lower depths. This local differentiation maintains geometry approximation precision where needed while reducing bitrate in areas where high precision is not necessary.
2Loss of information
If colors of all points are encoded, then color information completeness is improved, but bitrate increases significantly
Solution Approach 1:
The method extracts and encodes only the color information of representative points (one point per leaf octant) rather than encoding colors of all points in the point cloud. By taking out only the essential color data from each octant and using this representative color for approximation within the octant, the patent maintains color information completeness for visualization purposes while dramatically reducing the bitrate required for transmission.
Solution Approach 2:
The color of a single representative point in each leaf octant is encoded and then copied to represent all points within that octant. This copying approach allows the decoder to reconstruct color information for all points by assigning the representative color to the entire octant region, maintaining visual fidelity while minimizing the amount of color data that needs to be transmitted.
3Manufacturing precision
If up-sampling is performed to increase point density, then geometry detail is improved, but computational complexity and bitrate increase
Solution Approach 1:
The octree structure is constructed and representative points are selected in advance during the encoding phase. By performing the geometric approximation and representative point selection beforehand, the method prepares the data structure so that decoding can proceed more efficiently. The up-sampling and color assignment operations are based on pre-computed octant boundaries and representative points, reducing the computational complexity during actual decoding while still achieving high point density and geometry detail.
Data Source
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AI summary
The present principles a method and a device for encoding the colors of a point cloud (IPC) representing a 3D object. The method is characterized in that the method comprises: - obtaining (210) a set of points (SP) approximating the geometry of said point cloud (IPC); - encoding (220) a color information data indicating that the color of at least one of the point of said set of points is encoded in a bitstream and that the colors of the other points of said set of points are not encoded in the bitstream. The present principles also relates to a method and a device for decoding the colors of a point cloud.