The Transmission Control Protocol.

Since the popularisation of the Internet in the 1990s, the cyberspace has kept evolving. We have created various computer-mediated virtual environments including social networks, video conferencing, virtual 3D worlds (e.g., VR Chat), augmented reality applications (e.g., Pokemon Go), and Non-Fungible Token Games (e.g., Upland). Such virtual environments, albeit non-perpetual and unconnected, have bought us various degrees of digital transformation. The term `metaverse' has been coined to further facilitate the digital transformation in every aspect of our physical lives. At the core of the metaverse stands the vision of an immersive Internet as a gigantic, unified, persistent, and shared realm. While the metaverse may seem futuristic, catalysed by emerging technologies such as Extended Reality, 5G, and Artificial Intelligence, the digital `big bang' of our cyberspace is not far away. This survey paper presents the first effort to offer a comprehensive framework that examines the latest metaverse development under the dimensions of state-of-the-art technologies and metaverse ecosystems, and illustrates the possibility of the digital `big bang'. First, technologies are the enablers that drive the transition from the current Internet to the metaverse. We thus examine eight enabling technologies rigorously - Extended Reality, User Interactivity (Human-Computer Interaction), Artificial Intelligence, Blockchain, Computer Vision, IoT and Robotics, Edge and Cloud computing, and Future Mobile Networks. In terms of applications, the metaverse ecosystem allows human users to live and play within a self-sustaining, persistent, and shared realm. Therefore, we discuss six user-centric factors -- Avatar, Content Creation, Virtual Economy, Social Acceptability, Security and Privacy, and Trust and Accountability. Finally, we propose a concrete research agenda for the development of the metaverse.

All One Needs to Know about Metaverse: A Complete Survey on Technological Singularity, Virtual Ecosystem, and Research Agenda

Omnidirectional or 360° video is increasingly being used, mostly due to the latest advancements in immersive Virtual Reality (VR) technology. However, its wide adoption is hindered by the higher bandwidth and lower latency requirements than associated with traditional video content delivery. Diverse researchers propose and design solutions that help support an immersive visual experience of 360° video, primarily when delivered over a dynamic network environment. This paper presents the state-of-the-art on adaptive 360° video delivery solutions considering end-to-end video streaming in general and then specifically of 360° video delivery. Current and emerging solutions for adaptive 360° video streaming, including viewport-independent, viewport-dependent, and tile-based schemes are presented. Next, solutions for network-assisted unicast and multicast streaming of 360° video content are discussed. Different research challenges for both on-demand and live 360° video streaming are also analyzed. Several proposed standards and technologies and top international research projects are then presented. We demonstrate the ongoing standardization efforts for 360° media services that ensure interoperability and immersive media deployment on a massive scale. Finally, the paper concludes with a discussion about future research opportunities enabled by 360° video.

A Survey on Adaptive 360° Video Streaming: Solutions, Challenges and Opportunities

Virtual reality (VR) content, including 360° panoramic video, provides users with an immersive multimedia experience and therefore attracts increasing research and development attention. However, the requirement of high bandwidth and low latency of virtual reality service demand puts forward greater challenges to the current infrastructure, especially mobile networks. Inspired by the sharable nature of virtual reality content tiles, we further considered the potential opportunities for computing, caching, and multicast to address the challenges of transmission of panoramic content. This paper proposes a novel transcoding-enabled VR video caching and delivery framework for edge-enhanced next-generation wireless networks. Firstly, an edge cooperative caching scheme based on multi-agent reinforcement learning is introduced to improve the utilization efficiency of computing and storage resources, and then reduce service delay. Second, a two-tier NOMA-based base station-multicast group matching mechanism is designed to solve the collaboration challenge during the edge delivery process. A series of experiments have demonstrated the advantages of the proposed scheme in terms of cache hit rate, latency and other aspects in comparison with alternative approaches.

A Transcoding-Enabled 360° VR Video Caching and Delivery Framework for Edge-Enhanced Next-Generation Wireless Networks

BACKGROUND Research on the pedagogical use of immersive 360° videos is a rapidly expanding area within health and social care education. Despite this interest, there is a paucity of empirical data on its application. METHOD A scoping review methodology framework was used to search for relevant articles published between 1970 and July 2021. Six databases were used to identify studies using immersive 360° videos for training and education purposes within health and social care: PubMed, Ovid Medline, Psych Info, Psych Articles, Cochrane Database and Embase. Research questions included: Is there any evidence that immersive 360° videos increase learning outcomes and motivation to learn in health and social care education? What are the key pedagogical concepts and theories that inform this area of research? What are the limitations of using immersive 360° videos within health and social education? The four dimensions contained within Keller's ARCS model (attention, relevance, confidence and satisfaction) frame the results section. RESULTS Fourteen studies met our inclusion criteria. Learning outcomes confirm that immersive 360° videos as a pedagogical tool: increases attention, has relevance in skill enhancement, confidence in usability and user satisfaction. In particular, immersive 360° videos has a positive effect on the user's emotional response to the learning climate, which has a significant effect on users' motivation to learn. There was a notable lack of pedagogical theory within the studies retrieved and a general lack of clarity on learning outcomes. CONCLUSION Studies examining the effectiveness of such interventions remains weak due to smaller sample sizes, lack of randomised control trials, and a gap in reporting intervention qualities and outcomes. Nevertheless, 360° immersive video is a viable alternative to VR and regular video, it is cost-effective, and although more robust research is necessary, learning outcomes are promising. FUTURE DIRECTIONS Future research would do well to focus on interactivity and application of pedagogical theory within immersive 360° videos experiences. We argue that more and higher quality research studies, beyond the scope of medical education, are needed to explore the acceptability and effective implementation of this technology.

Immersive 360° videos in health and social care education: a scoping review.

Recently, 360° or omnidirectional videos have become increasingly popular for both personal and enterprize use-cases. However, 360° video streaming has very high bandwidth and processing requirements. State-of-the-art viewport-based streaming solutions lower these requirements by performing selective streaming based on long-term Field-of-View (FoV) prediction mechanisms. However, sometimes user movement is extremely unpredictable during some parts of the video, and applying these solutions adversely affects the overall quality of experience (QoE). This paper proposes a novel Combined Field-of-View tile-based adaptive streaming solution (CFOV) that improves end-user QoE for 360° video streaming. CFOV performs interactive tile selection based on more accurate dynamical viewing area identification by combining the results of two FoV prediction mechanisms. It also employs an innovative priority-based bitrate adaptation approach that ensures improved bitrate budget distribution between different tiles. We evaluate the proposed solution with a comprehensive set of experiments involving four immersive videos, diverse tiling patterns (i.e., 4×3, 6×4, and 8×6), different segment lengths (i.e., 1s, 2s, and 3s), and 48 empirical head movement traces under different bandwidth settings. The evaluation employs a newly defined QoE metric specifically introduced to assess the streaming performance of 360° videos objectively. The experimental findings show that, compared to alternative approaches, our proposed solution can achieve a higher viewport match and can significantly improve the user QoE for different watching behaviors and content characteristics.

/pdf/a-combined-field-of-view-prediction-assisted-viewport-2hr9tf68xd.pdf

A Combined Field-of-View Prediction-Assisted Viewport Adaptive Delivery Scheme for 360° Videos

Today, the dynamic network environment poses severe challenging issues to multimedia streaming services that account for an enormous part of network traffic all over the world. Dynamic adaptive streaming over HTTP (DASH) facilitates seamless video playback by allowing for dynamic adjustment of the video bitrate to the ongoing network situation. Despite several attempts, there is still a challenge to design solutions which use DASH to adjust video delivery to the dynamic network environment and achieve high user quality of experience levels. This paper presents a novel DASH-based throughput and buffer occupancy-based adaptation (TBOA) algorithm to provide an improved streaming experience for remote users. TBOA was compared against alternative solutions such as FDASH and SFTM in single- and multiple-client scenarios. Testing results show how TBOA selects higher video bitrates while performing fewer video bitrate switches and reduces the risk of buffer underrun in comparison with the competitors.

A DASH-based Efficient Throughput and Buffer Occupancy-based Adaptation Algorithm for Smooth Multimedia Streaming

Recently, affordable virtual reality (VR) technology has experienced increased attention as it enables innovative and immersive 360° media applications. However, the expected immersive rich media streaming experience is hindered by excessive bandwidth requirements of high-resolution 360° content. It is essential to devise technologies that enable persistent delivery of such bandwidth-hungry applications over the best-effort packet networks. Tile-based adaptive streaming is one of such techniques that support differentiated streaming of quality-variable tiles depending on their position within the viewport. This paper proposes a weighted tile-based approach for 360° video streaming. First, a content-agnostic viewport prediction approach is proposed. Second, a novel viewport and bitrate adaptation heuristic solution which dynamically selects the coverage of the viewport and its marginal regions and allocates weights to the tiles in these regions is introduced. Finally, suitable video bitrates for each tile based on its weight and available network throughput is allocated. The solution is tested and assessed in comparison with alternative approaches resulting in improved viewport quality and lower bandwidth utilization.

A Weighted Tile-based Approach for Viewport Adaptive 360° Video Streaming

Interactive 360° remote video applications have seen booming advancements due to the proliferation of smart display devices that enable a truly immersive experience. Compared to regular monoscopic videos, 360° videos have different requirements related to content preparation, packaging, transmission, specialized viewing equipment, and display factors (e.g., brightness, contrast, delay, frame rate, resolution, image quality, etc. In addition, 360° video requires substantial network and computational resources, which are challenging to achieve with conventional transmission and rendering infrastructure. Viewport-adaptive streaming is a common way to ensure visual quality under limited bandwidth resources. However, identifying, extracting, and rendering the true viewport in response to drastic head rotations can adversely affect user experience. This paper proposes two dynamic viewport selection approaches, which adapt the streamed regions based on content complexity variations and positional information to ensure viewport availability and smooth visual angles for VR users. They incorporate content information as well as user head movement patterns to support tile-based prioritized 360° video streaming. Moreover, a practical, prioritized bitrate adaptation approach, which requests selected tiles at appropriate quality levels, is also proposed to reduce the impact of inefficient bandwidth utilization in the VR scene. Experimental evaluations under real 4G bandwidth logs demonstrate that the proposed solutions outperform the closest state-of-theart algorithms across multiple performance metrics, i.e., viewport overlap, perceived quality levels, quality fluctuations, and viewport bandwidth utilization.

https://ieeexplore.ieee.org/ielx7/6287639/9668973/09729728.pdf

Abid Yaqoob

Papers

A Survey on Adaptive 360° Video Streaming: Solutions, Challenges and Opportunities

A Combined Field-of-View Prediction-Assisted Viewport Adaptive Delivery Scheme for 360° Videos

A DASH-based Efficient Throughput and Buffer Occupancy-based Adaptation Algorithm for Smooth Multimedia Streaming

A Weighted Tile-based Approach for Viewport Adaptive 360° Video Streaming

Dynamic Viewport Selection-based Prioritized Bitrate Adaptation for Tile-based 360. Video Streaming