Volumetric video (VV) has emerged as a prominent medium within the realm of extended reality (XR) with advancements in computer graphics and depth capture hardware. Users can fully immersive themselves in VV with the ability to switch their viewport in six degree of freedom (DOF), including three rotational dimensions (yaw, pitch, and roll) and three translational dimensions (X, Y, and Z). Different from traditional 2-D videos that are composed of pixel matrices, VVs employ point clouds, meshes, or voxels to represent a volumetric scene, resulting in significantly larger data sizes. While previous works have successfully achieved VV streaming in video-on-demand scenarios, the live streaming of VV remains an unresolved challenge due to the limited network bandwidth and stringent latency constraints. In this article, we proposeLiveVV, a holistic live VV streaming system that integrates multiview capture, scene segmentation and reuse, adaptive transmission, and real-time rendering.LiveVVfeatures lightweight VV capture modules for easy deployment, processes static and dynamic content separately to reduce bandwidth consumption, and incorporates a VV adaptive bitrate streaming algorithm (VABR) to ensure fluent playback with high-quality experience. Real-world implementation and evaluation demonstrate thatLiveVVachieves live VV streaming at 24 FPS frame rate with less than 350-ms latency on average, meeting the requirements of real-life application.

Point cloud video (PCV) offers watching experiences in photorealistic 3D scenes with six-degree-of-freedom (6-DoF), enabling a variety of VR and AR applications. The user's Field of View (FoV) is more fickle with 6-DoF movement than 3-DoF movement in 360-degree video. PCV streaming is extremely bandwidth-intensive. However, current streaming systems require hundreds of Mbps bandwidth, exceeding the bandwidth capabilities of commodity devices. To save bandwidth, FoV-adaptive streaming predicts a user's FoV and only downloads point cloud data falling in the predicted FoV. But it is difficult to accurately predict the user's FoV even 2-3 seconds before playback due to 6-DoF. Misprediction of FoV or network bandwidth dips results in frequent stalls. To avoid rebuffering, existing systems would cause incomplete FoV and degraded experience, deteriorating the user's quality of experience (QoE). In this paper, we describe Fumos, a novel system that preserves interactive experience by avoiding playback stalls while maintaining high perceptual quality and high compression rate. We find a research gap in inter-frame redundant utilization and progressive mechaism. Fumos has three crucial designs, including (1) Neural compression framework with inter-frame coding, namely N-PCC, which achieves both bandwidth efficiency and high fidelity. (2) Progressive refinement streaming framework that enables continuous playback by incrementally upgrading a fetched portion to a higher quality (3) System-level adaptation that employs Lyapunov optimization to jointly optimize the long-term user QoE. Experimental results demonstrate that Fumos significantly outperforms Draco, achieving an average decoding rate acceleration of over 260×. Moreover, the proposed compression framework N-PCC attains remarkable BD-Rate gains, averaging 91.7% and 51.7% against the state-of-the-art point cloud compression methods G-PCC and V-PCC, respectively.

Volumetric video emerges as a new attractive video paradigm in recent years since it provides an immersive and interactive 3D viewing experience with six degree-of-freedom (DoF). Unlike traditional 2D or panoramic videos, volumetric videos require dense point clouds, voxels, meshes, or huge neural models to depict volumetric scenes, which results in a prohibitively high bandwidth burden for video delivery. Users' behavior analysis, especially the viewport and gaze analysis, then plays a significant role in prioritizing the content streaming within users' viewport and degrading the remaining content to maximize user QoE with limited bandwidth. Although understanding user behavior is crucial, to the best of our best knowledge, there are no available 3D volumetric video viewing datasets containing fine-grained user interactivity features, not to mention further analysis and behavior prediction.

Recent years have witnessed a rapid development of immersive multimedia which bridges the gap between the real world and virtual space. Volumetric videos, as an emerging representative 3D video paradigm that empowers extended reality, stand out to provide unprecedented immersive and interactive video watching experience. Despite the tremendous potential, the research towards 3D volumetric video is still in its infancy, relying on sufficient and complete datasets for further exploration. However, existing related volumetric video datasets mostly only include a single object, lacking details about the scene and the interaction between them. In this paper, we focus on the current most widely used data format, point cloud, and for the first time release a full-scene volumetric video dataset that includes multiple people and their daily activities interacting with the external environments. Comprehensive dataset description and analysis are conducted, with potential usage of this dataset. The dataset and additional tools can be accessed via the following website: https://cuhksz-inml.github.io/full_scene_volumetric_video_dataset/.

Volumetric video (VV) recently emerges as a new form of video application providing a photorealistic immersive 3D viewing experience with 6 degree-of-freedom (DoF), which empowers many applications such as VR, AR, and Metaverse. A key problem therein is how to stream the enormous size VV through the network with limited bandwidth. Existing works mostly focused on predicting the viewport for a tiling-based adaptive VV streaming, which however only has quite a limited effect on resource saving. We argue that the content repeatability in the viewport can be further leveraged, and for the first time, propose a client-side cache-assisted strategy that aims to buffer the repeatedly appearing VV tiles in the near future so as to reduce the redundant VV content transmission. The key challenges exist in three aspects, including (1) feature extraction and mining in 6 DoF VV context, (2) accurate long-term viewing pattern estimation and (3) optimal caching scheduling with limited capacity. In this paper, we propose CaV3, an integrated cache-assisted viewport adaptive VV streaming framework to address the challenges. CaV3 employs a Long-short term Sequential prediction model (LSTSP) that achieves accurate short-term, mid-term and long-term viewing pattern prediction with a multi-modal fusion model by capturing the viewer's behavior inertia, current attention, and subjective intention. Besides, CaV3 also contains a contextual MAB-based caching adaptation algorithm (CCA) to fully utilize the viewing pattern and solve the optimal caching problem with a proved upper bound regret. Compared to existing VV datasets only containing single or co-located objects, we for the first time collect a comprehensive dataset with sufficient practical unbounded 360° scenes. The extensive evaluation of the dataset confirms the superiority of CaV3, which outperforms the SOTA algorithm by 15.6%-43% in viewport prediction and 13%-40% in system utility.

As one of the most important manifestations of virtual reality (VR), 360° panoramic videos in recent years have experienced booming development due to the desire for immersive and interactive experiences. Compared to traditional videos, 360° videos are featured with uncertain user Field of View (FoV), more sensitive delay tolerance, and much higher bandwidth requirement, bringing unprecedented challenges to 360° video streaming. Meanwhile, the development of 5G and mobile edge computing starts to pave the way for high-bandwidth low-latency video streaming. Some preliminary works focus on either individual FoV prediction or multiuser Quality of Experience (QoE) oriented cache strategy design, while how to design a holistic solution toward optimizing the overall user QoE with considerations over fairness and long-term system cost remains a nontrivial problem. In this article, we proposeEbublio, a novel intelligent edge caching framework to address the aforementioned challenges in 360° video streaming.Ebublioconsists of a collaborative FoV prediction (CFP) module and a long-term tile caching optimization (LTO) module to jointly optimize the long-term user QoE and system cost. The former module integrates the features of video content, user trajectory, and other users’ records for combined prediction. The latter one employs the Lyapunov framework and a subgradient optimization approach toward the optimal caching replacement policy. Our trace-driven evaluation demonstrates the superiority of our framework, with about 42% improvement in FoV prediction, and 36% improvement in QoE at similar traffic consumption.

360° videos in recent years have experienced booming development. Compared to traditional videos, 360° videos are featured with uncertain user behaviors, bringing opportunities as well as challenges. Datasets are necessary for researchers and developers to explore new ideas and conduct reproducible analyses for fair comparisons among different solutions. However, existing related datasets mostly focused on users' field of view (FoV), ignoring the more important eye gaze information, not to mention the integrated extraction and analysis of both FoV and eye gaze. Besides, users' behavior patterns are highly related to videos, yet most existing datasets only contained videos with subjective and qualitative classification from video genres, which lack quantitative analysis and fail to characterize the intrinsic properties of a video scene. To this end, we first propose a quantitative taxonomy for 360° videos that contains three objective technical metrics. Based on this taxonomy, we collect a dataset containing users' head and gaze behaviors simultaneously, which outperforms existing datasets with rich dimensions, large scale, strong diversity, and high frequency. Then we conduct a pilot study on users' behaviors and get some interesting findings such as user's head direction will follow his/her gaze direction with the most possible time interval. A case of application in tile-based 360° video streaming based on our dataset is later conducted, demonstrating a great performance improvement of existing works by leveraging our provided gaze information. Our dataset is available at https://cuhksz-inml.github.io/head_gaze_dataset/