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面向AVS点云压缩标准的八叉树上下文模型优化

Optimized Octree Coding for AVS Point Cloud Compression Standard

  • 摘要: 中国数字音视频编解码技术标准工作组制定的点云压缩标准《信息技术 时空图形数据编码 第2部分:点云》(即AVS-PCC)已于2024年10月颁布. 在AVS-PCC几何压缩部分的八叉树编码中,现有方法根据点云密度经验性地构建了两种不统一的上下文模型,无法高效去除空间冗余. 针对该问题,提出基于统一上下文模型的八叉树编码方法. 面向各类不同密度的点云,设计统一的策略为当前子节点构建基于邻域几何信息的状态模型;提出基于有限计数器的概率估计方法对各状态模型中的状态概率进行估计;进而根据状态概率估计结果构建统一上下文模型,并利用基于上下文的自适应二进制算术编码器进行熵编码. 在通用测试条件下与现有方法相比,所提方法提升了AVS-PCC的有损和无损几何压缩性能,平均性能增益分别为2.5%和1.2%.

     

    Abstract: The point cloud compression standard “Information Technology Space-Time Graphical Data Coding Part 2: Point Cloud” (i.e. AVS-PCC), developed by the Audio Video Coding Standard Workgroup of China, was promulgated in October 2024. In the octree coding of the geometry compression part in AVS-PCC, the existing method empirically constructs two non-uniform context models based on point cloud density, which is an ineffective approach for the removal of spatial redundancy. To address this issue, a uniform context model based octree coding method is proposed. Firstly, for various types of point clouds with different densities, a uniform strategy is designed to construct state models based on the neighboring geometry information for the current sub-node. Secondly, a finite counter based probability estimation method is proposed to estimate the probabilities of different states in each state model. Finally, a uniform context model is generated guided by the results of the probability estimation. The current sub-node is then compressed using the context-based adaptive binary arithmetic codec. In comparison to the existing method under Common Test Conditions, the proposed method has enhanced the lossy and lossless geometry compression performance of AVS-PCC, with overall average performance gains of 2.5% and 1.2%, respectively.

     

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