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[转载]【计算机科学】【2017.11】动态三维点云压缩

已有 492 次阅读 2020-6-23 14:52 |系统分类:科研笔记|文章来源:转载

本文为葡萄牙里斯本技术学院(作者:Miguel Branco RoqueNazaré Ferreira)的硕士论文,共110页。

 

点云是通过三维坐标系中的一组点对全光函数进行采样而获得的表示模型,具有可选的相关属性,例如颜色、表示对象或表面。近年来,在视觉信息的获取和显示方面取得了一些新的进展,如3D沉浸式临场感和3D体育广播等。因此,一项具有挑战性的任务是以有效的方式表示和编码必要的视觉信息,以便于存储、传输和处理这些数据。对于动态点云,即随时间变化的点云,编码解决方案的开发仍处于非常初始的阶段,还有很大的改进空间。最近,MPEG集团在这个领域发起了一个标准化项目。

 

考虑到现有的动态点云编码解决方案不多,本文提出了一种同时利用动态点云时空相关性的新方案。该方案利用点描述符估计当前帧和以前帧之间的运动,建立两帧中点之间的对应关系,用几何变换(homography)对运动进行建模,然后生成一个具有一定扭曲步进的运动补偿帧。再对运动补偿帧和目标帧之间的差异进行编码和传输,如基于八叉树的双缓冲点云库(PCL)编解码器。计算结果表明,当两个连续帧之间存在高速运动时,运动补偿帧比前一帧具有更好的预测性能。然而,RD性能评估表明,这种改进不足以使所提出的解决方案在速率失真方面优于使用历史编码帧的原始PCL编解码器。

 

Point clouds are a representation model obtained from the samplingof the plenoptic function through a set of points in a 3D coordinate system,with optional associated attributes, e.g. the colours, representing objects orsurfaces. Recent advances in capturing and displaying of visual information areenabling more immersive and realistic user experiences, such as 3D immersivetelepresence and 3D sports broadcasting. Thus, a challenging task consists inrepresenting and coding the necessary visual information in an efficient way,to facilitate the storage, transmission and processing of such data. For dynamicpoint clouds, i.e. point clouds changing through time, the development ofcoding solutions is still at a very initial phase, with large room forimprovements. Recently, the MPEG group has launched a standardization projectin this field.
Considering the few dynamic point cloud coding solutions available in theliterature, this Thesis proposes a novel solution to exploit both temporal andspatial correlations in a dynamic point cloud. The proposed solution estimatesmotion between the current and previous frames by using point descriptors, establishingcorrespondences between points in the two frames, modelling the motion with ageometric transform (homography) and then producing a motion compensated framewith some warping step. Then, the differences between the motion compensatedand target frames are encoded and transmitted, as in the octree-based doublebuffering Point Cloud Library (PCL) codec. The evaluation shows that the motioncompensated frame has a better prediction than the previous frame, when thereis high motion between two successive frames. However, the RD performance assessmentshows that this improvement is not enough for the proposed solution tooutperform in rate distortion the original PCL codec, which uses the past codedframe.

 

1. 引言

2. 点云:基本和主要编码解决方案

3. 基于单应的点云编解码器:体系结构与工具

4. 性能评估

5. 结论与未来工作展望

附录文献中关于点云描述符的综述

附录B PCL中可用聚类技术综述

附录时间预测Rmse评估图



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