Intra-Frame Context-Based Octree Coding for Point-Cloud Geometry

3D and free-viewpoint video has been slowly adopting a solid representation, such as using meshes and point-clouds. Among other characteristics, meshes provide direct surface representation, while point-cloud processing requires less computation. Points in the cloud are minimally represented by their geometry (3D position) and color. A common point-cloud geometry compression method is the octree representation, which acts on individual frames and can be further compressed by entropy encoding. This paper presents a lossless intra-frame compression method for point-cloud geometry, which uses the octree structure to provide better contexts for entropy coding. Results show that the proposed solution offers state-of-the-art performance, with an average rate reduction of 29% compared to the octree representation.

I. Introduction

In the past few years, 3D visual communications have developed tremendously, allowing for the real-time capture and transmission of events [1]–[3]. Several space-time representations are then made possible, each with different characteristics. Multiview-plus-depth video is based on multiple 2D projections of 3D scenes, which can then be efficiently compressed, for example, with the multiview extension of the High Efficiency Video Coding standard, MV-HEVC [4] [5]. Polygonal meshes, on the other hand, represent 3D scenes with connected polygons [6]. Point-clouds also directly represent 3D scenes (Fig. 1), but by indicating points' colors in 3D space (voxels) [3].