Due to the increased popularity of augmented and virtual reality experiences, the interest in capturing the real world in multiple dimensions and in presenting it to users in an immersible fashion has never been higher. Distributing such representations enables users to freely navigate in multi-sensory 3D media experiences. Unfortunately, such representations require a large amount of data, not feasible for transmission on today's networks. Efficient compression technologies well adopted in the content chain are in high demand and are key components to democratize augmented and virtual reality applications. The Moving Picture Experts Group, MPEG, as one of the main standardization groups dealing with multimedia, identified the trend and started recently the process of building an open standard for compactly representing 3D point clouds, which are the 3D equivalent of the very well-known 2D pixels. This paper introduces the main developments and technical aspects of this ongoing standardization effort.

Abstract-we present a generic and real-time time-varying point cloud codec for 3D immersive video. This codec is suitable for mixed reality applications where 3D point clouds are acquired at a fast rate. In this codec, intra frames are coded progressively in an octree subdivision. To further exploit interframe dependencies, we present an inter-prediction algorithm that partitions the octree voxel space in N times N times N macroblocks (N=8,16,32). The algorithm codes points in these blocks in the predictive frame as a rigid transform applied to the points in the intra coded frame. The rigid transform is computed using the iterative closest point algorithm and compactly represented in a quaternion quantization scheme. To encode the color attributes, we defined a mapping of color per vertex attributes in the traversed octree to an image grid and use legacy image coding method based on JPEG. As a result, a generic compression framework suitable for real-time 3D tele-immersion is developed. This framework has been optimized to run in realtime on commodity hardware for both encoder and decoder. Objective evaluation shows that a higher rate-distortion (R-D) performance is achieved compared to available point cloud codecs. A subjective study in a state of art mixed reality system shows that introduced prediction distortions are negligible compared to the original reconstructed point clouds. In addition, it shows the benefit of reconstructed point cloud video as a representation in the 3D Virtual world. The codec is available as open source for integration in immersive and augmented communication applications and serves as a base reference software platform in JCT1/SC29/WG11 (MPEG) for the further development of standardized point cloud compression solutions.

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Millions of photos are shared online daily, but the richness of interaction compared with face-to-face (F2F) sharing is still missing. While this may change with social Virtual Reality (socialVR), we still lack tools to measure such immersive and interactive experiences. In this paper, we investigate photo sharing experiences in immersive environments, focusing on socialVR. Running context mapping (N=10), an expert creative session (N=6), and an online experience clustering questionnaire (N=20), we develop and statistically evaluate a questionnaire to measure photo sharing experiences. We then ran a controlled, within-subject study (N=26 pairs) to compare photo sharing under F2F, Skype, and Facebook Spaces. Using interviews, audio analysis, and our questionnaire, we found that socialVR can closely approximate F2F sharing. We contribute empirical findings on the immersiveness differences between digital communication media, and propose a socialVR questionnaire that can in the future generalize beyond photo sharing.