Rate-Distortion Optimized Skip Coding of Region Adaptive Hierarchical Transform Coefficients for MPEG G-PCC

TL;DR

This paper introduces an adaptive skip coding method for RAHT in G-PCC, significantly reducing bitrate while maintaining quality for 3D point cloud compression.

Contribution

It proposes a novel adaptive skip coding approach with rate-distortion optimization for RAHT in G-PCC, enhancing compression efficiency.

Findings

Achieves average bitrate reductions of around 3.5% to 5.6% across components.

Improves coding efficiency by adaptively skipping residuals in RAHT layers.

Demonstrates effectiveness on dynamic point clouds under MPEG test conditions.

Abstract

Three-dimensional (3D) point clouds are becoming more and more popular for representing 3D objects and scenes. Due to limited network bandwidth, efficient compression of 3D point clouds is crucial. To tackle this challenge, the Moving Picture Experts Group (MPEG) is actively developing the Geometry-based Point Cloud Compression (G-PCC) standard, incorporating innovative methods to optimize compression, such as the Region-Adaptive Hierarchical Transform (RAHT) nestled within a layer-by-layer octree-tree structure. Nevertheless, a notable problem still exists in RAHT, i.e., the proportion of zero residuals in the last few RAHT layers leads to unnecessary bitrate consumption. To address this problem, we propose an adaptive skip coding method for RAHT, which adaptively determines whether to encode the residuals of the last several layers or not, thereby improving the coding efficiency. In addition, we propose a rate-distortion cost calculation method associated with an adaptive Lagrange multiplier. Experimental results demonstrate that the proposed method achieves average Bj{\o}ntegaard rate improvements of -3.50%, -5.56%, and -4.18% for the Luma, Cb, and Cr components, respectively, on dynamic point clouds, when compared with the state-of-the-art G-PCC reference software under the common test conditions recommended by MPEG.