Point Cloud Compression (PCC) algorithms can be roughly categorized into: (i) traditional Signal-Processing (SP) based and, more recently, (ii) Machine-Learning (ML) based. PCC algorithms are often evaluated with very different datasets, metrics, and parameters, which in turn makes the evaluation results hard to interpret. In this paper, we propose an open-source benchmark, called PCC Arena, which consists of several point cloud datasets, a suite of performance metrics, and a unified procedure. To demonstrate its practicality, we employ PCC Arena to evaluate three SP-based and one ML-based PCC algorithms. We also conduct a user study to quantify the user experience on rendered objects reconstructed from different PCC algorithms. Several interesting insights are revealed in our evaluations. For example, SP-based PCC algorithms have diverse design objectives and strike different trade-offs between coding efficiency and time complexity. Furthermore, although ML-based PCC algorithms are quite promising, they may suffer from long running time, unscalability to diverse point cloud densities, and high engineering complexity. Nonetheless, ML-based PCC algorithms are worth of more in-depth studies, and PCC Arena will play a critical role in the follow-up research for more interpretable and comparable evaluation results.

The popularity of computer games is remarkably high and is still growing. Despite the popularity and economical impact of games, data-driven research in game design, or to be more precise, in-game mechanics - game elements and rules defining how a game works - is still scarce. As data on user interaction in games is hard to get by, we propose a way to analyze players' movement and action based on video streams of games. Utilizing this data we formulate four hypotheses focusing on player experience, enjoyment, and interaction patterns, as well as the interrelation thereof. Based on a user study for the popular game Fortnite, we discuss the interrelation between game mechanics, enjoyment of players, and different player skill levels in the observed data.

By allowing people to manipulate digital content placed in the real world, Augmented Reality (AR) provides immersive and enriched experiences in a variety of domains. Despite its increasing popularity, providing a seamless AR experience under bandwidth fluctuations is still a challenge, since delivering these experiences at photorealistic quality with minimal latency requires high bandwidth. Streaming approaches have already been proposed to solve this problem, but they require accurate prediction of the Field-Of-View of the user to only stream those regions of scene that are most likely to be watched by the user. To solve this prediction problem, we study in this paper the watching behavior of users exploring different types of AR scenes via mobile devices. To this end, we introduce the ACE Dataset, the first dataset collecting movement data of 50 users exploring 5 different AR scenes. We also propose a four-feature taxonomy for AR scene design, which allows categorizing different types of AR scenes in a methodical way, and supporting further research in this domain. Motivated by the ACE dataset analysis results, we develop a novel user visual attention prediction algorithm that jointly utilizes information of users' historical movements and digital objects positions in the AR scene. The evaluation on the ACE Dataset show the proposed approach outperforms baseline approaches under prediction horizons of variable lengths, and can therefore be beneficial to the AR ecosystem in terms of bandwidth reduction and improved quality of users' experience.

To cope with the large bandwidth and low-latency requirements, Virtual Reality (VR) systems are steering toward user-centric systems in which coding, streaming, and possibly rendering are personalized to the final user. The success of these user-centric VR systems mainly relies on the ability to anticipate viewers navigation. This has motivated a large attention in studying the prediction of user's movements in a VR experience. However, most of these work lack of a proper and exhaustive behavioural analysis in a VR scenario, leaving many key-behavioural questions unsolved and unexplored: Can some users be more predictable than others? Do users have their own way of navigating and how much is this affected by the video content features? Can we quantify the similarity of users navigation? Answering these questions is a crucial step toward the understanding of user's behaviour in VR; and it is the overall goal of this paper. By studying VR trajectories across different contents and through information-theoretic tools, we aim at characterizing navigation patterns both for each single viewer (profiling individually viewers - intra-user analysis) and for a multitude of viewers (identifying common patterns among viewers - inter-user analysis). For each of these proposed behavioural analyses, we describe the applied metrics and key observations that can be extrapolated.

Cloud Gaming is an emerging service that catches growing interest in the research community as well as industry. Cloud Gaming require a highly reliable and low latency network to achieve a satisfying Quality of Experience (QoE) for its users. Using a cloud gaming service with high latency would harm the interaction of the user with the game, leading to a decrease in playing performance and, thus players frustrations. However, the negative effect of delay on gaming QoE depends strongly on the game content. At a certain level of delay, a slow-paced card game is typically not as delay sensitive as a shooting game. For optimal resource allocation and quality estimation, it is highly important for cloud providers, game developers, and network planners to consider the impact of the game content. This paper contributes to a better understanding of the delay impact on QoE for cloud gaming applications by identifying game characteristics influencing the delay perception of the users. In addition, an expert evaluation methodology to quantify these characteristics as well as a delay sensitivity classification based on a decision tree are presented. The results indicated an excellent level of agreement, which demonstrates the reliability of the proposed method. Additionally, the decision tree reached an accuracy of 90% on determining the delay sensitivity classes which were derived from a large dataset of subjective input quality ratings during a series of experiments.