In recent years, video conferencing platforms have become powerful tools for remote communication. There has also been an increase in the use of VR systems for communication. However, very few of these systems utilize photorealistic human representation. This paper investigates the strengths, challenges, and limitations of a novel 3D communication prototype (VR2Gather) and a well-established video conferencing system (Zoom). Specifically, we explore whether the 3D communication prototype can achieve comparable performance levels in a remote physiotherapy use case. By assessing various aspects, such as audio-visual quality, presence, and interaction, we aim to determine if the current prototype is comparable with commercial systems in some dimensions while exceeding expectations in others. Our results indicated that VR2Gather has the potential for a better sense of connection and higher concentration. However, challenges like improving 3D rendering quality and communication ease still need to be overcome to make it suitable for physiotherapy.

Cloud Virtual Reality (VR) gaming offloads computationally intensive VR games to resourceful data centers. However, ensuring good Quality of Experience (QoE) in cloud VR gaming is inherently challenging as VR gamers demand high visual quality, short response time, and negligible cybersickness. In this article, we study the QoE of cloud VR gaming and build a QoE-optimized system in a few steps. First, we establish a cloud VR gaming testbed capable of emulating various network conditions. Using the testbed, we conduct comprehensive QoE evaluations using a user study to evaluate the influence of diverse factors, such as encoding settings, network conditions, and game genres, on gamer QoE scores. Second, we construct the very first QoE models for cloud VR gaming using our QoE evaluation results. Our QoE models achieve up to 0.93 ( \(\sigma=0.02\) ) in Pearson Linear Correlation Coefficient (PLCC) and 0.92 ( \(\sigma=0.02\) ) in Spearman Rank-Order Correlation Coefficient (SROCC), where \(\sigma\) stands for the standard deviation. Last, we leverage our QoE models for dynamically adapting encoding settings in our testbed. Extensive experiments revealed that, compared to the current practice, our adaptive cloud VR gaming system improves: (i) overall quality by 0.87 ( \(\sigma=0.44\) ), (ii) visual quality by 0.61 ( \(\sigma=0.45\) ), and (iii) interaction quality by 1.20 ( \(\sigma=0.48\) ) on average in 5-point Mean Opinion Score (MOS).

Extended Reality (XR) has emerged as a transformative and immersive technology with versatile applications in content creation and consumption. As XR gains popularity, companies eager to adopt it often possess a surface-level understanding, investing significant resources without effectively addressing the genuine needs of end-users. This study explores the current workflows of XR production companies, and the potential of social XR in mitigating challenges throughout the XR production workflow. We present the outcomes of three respective focus group workshops conducted with three XR production companies and their experts (N=17). The results indicate that at every stage of the production, namely pre-production, production, post-production, and post-release, there are communication challenges between producers and clients, as well as different production and post-production specialists. We discuss various aspects of XR concerning the problem and propose novel opportunities offered by social XR to ameliorate those challenges, improving communication and making development more agile.

There is an increased interest in understanding users' behavior when exploring omnidirectional (360°) videos, especially in the presence of spatial audio. Several studies demonstrate the effect of no, mono, or spatial audio on visual saliency. However, no studies investigate the influence of higher-order (i.e., 4t h- order) Ambisonics on subjective exploration in virtual reality settings. In this work, a between-subjects test design is employed to collect users' exploration data of 360° videos in a free-form viewing scenario using the Varjo XR-3 Head Mounted Display, in the presence of no, mono, and 4th-order Ambisonics audio. Saliency information was captured as head-saliency in terms of the center of a viewport at 50 Hz. For each item, subjects were asked to describe the scene with a short free-verbalization task. Moreover, cybersickness was assessed using the simulator sickness questionnaire at the beginning and at the end of the test. The head-saliency results over time show that with the presence of higher-order Ambisonics audio, subjects concentrate more on the directions sound is coming from. No influence of audio scenario on cybersickness scores was observed. From the analysis of the verbal scene descriptions, it was found that users were attentive to the omnidirectional video, but only for the ‘no audio’ scenario provided minute and insignificant details of the scene objects. The audiovisual saliency dataset is made available following the open science approach already used for the audiovisual scene recordings we previously published. The data is sought to enable training of visual and audiovisual saliency prediction models for interactive experiences.

This study uses a mixed between- and within-subjects test design to evaluate the influence of interactive formats on the quality of binaurally rendered 360° spatial audio content. Focusing on ecological validity using real-world recordings of 60 s duration, three independent groups of subjects () were exposed to three formats: audio only (A), audio with 2D visuals (A2DV), and audio with head-mounted display (AHMD) visuals. Within each interactive format, two sessions were conducted to evaluate degraded audio conditions: bit-rate and Ambisonics order. Our results show a statistically significant effect (p < .05) of format only on spatial audio quality ratings for Ambisonics order. Exploration data analysis shows that format A yields little variability in exploration, while formats A2DV and AHMD yield broader viewing distribution of 360° content. The results imply audio quality factors can be optimized depending on the interactive format.

Research into multi-modal perception, human cog-nition, behavior, and attention can benefit from high-fidelity content that may recreate real-life-like scenes when rendered on head-mounted displays. Moreover, aspects of audiovisual perception, cognitive processes, and behavior may complement questionnaire-based Quality of Experience (QoE) evaluation of interactive virtual environments. Currently, there is a lack of high-quality open-source audiovisual databases that can be used to evaluate such aspects or systems capable of reproducing high-quality content. With this paper, we provide a publicly available audiovisual database consisting of twelve scenes capturing real-life nature and urban environments with a video resolution of 7680×3840 at 60 frames-per-second and with 4th-order Ambison-ics audio. These 360° video sequences, with an average duration of 60 seconds, represent real-life settings for systematically evaluating various dimensions of uni-/multi-modal perception, cognition, behavior, and QoE. The paper provides details of the scene requirements, recording approach, and scene descriptions. The database provides high-quality reference material with a balanced focus on auditory and visual sensory information. The database will be continuously updated with additional scenes and further metadata such as human ratings and saliency information.

Recently an impressive development in immersive technologies, such as Augmented Reality (AR), Virtual Reality (VR) and 360${^\circ }$video, has been witnessed. However, methods for quality assessment have not been keeping up. This paper studies quality assessment of 360${^\circ }$video from the cross-lab tests (involving ten laboratories and more than 300 participants) carried out by the Immersive Media Group (IMG) of the Video Quality Experts Group (VQEG). These tests were addressed to assess and validate subjective evaluation methodologies for 360${^\circ }$video. Audiovisual quality, simulator sickness symptoms, and exploration behavior were evaluated with short (from 10 seconds to 30 seconds) 360${^\circ }$sequences. The following factors’ influences were also analyzed: assessment methodology, sequence duration, Head-Mounted Display (HMD) device, uniform and non-uniform coding degradations, and simulator sickness assessment methods. The obtained results have demonstrated the validity of Absolute Category Rating (ACR) and Degradation Category Rating (DCR) for subjective tests with 360${^\circ }$videos, the possibility of using 10-second videos (with or without audio) when addressing quality evaluation of coding artifacts, as well as any commercial HMD (satisfying minimum requirements). Also, more efficient methods than the long Simulator Sickness Questionnaire (SSQ) have been proposed to evaluate related symptoms with 360${^\circ }$videos. These results have been instrumental for the development of the ITU-T Recommendation P.919. Finally, the annotated dataset from the tests is made publicly available for the research community.

Virtual Reality/360° videos provide an immersive experience to users. Besides this, 360° videos may lead to an undesirable effect when consumed with Head-Mounted Displays (HMDs), referred to as simulator sickness/cybersickness. The Simulator Sickness Questionnaire (SSQ) is the most widely used questionnaire for the assessment of simulator sickness. Since the SSQ with its 16 questions was not designed for 360° video related studies, our research hypothesis in this paper was that it may be simplified to enable more efficient testing for 360° video. Hence, we evaluate the SSQ to reduce the number of questions asked from subjects, based on six different previously conducted studies. We derive the reduced set of questions from the SSQ using Principal Component Analysis (PCA) for each test. Pearson Correlation is analysed to compare the relation of all obtained reduced questionnaires as well as two further variants of SSQ reported in the literature, namely Virtual Reality Sickness Questionnaire (VRSQ) and Cybersickness Questionnaire (CSQ). Our analysis suggests that a reduced questionnaire with 9 out of 16 questions yields the best agreement with the initial SSQ, with less than 44% of the initial questions. Exploratory Factor Analysis (EFA) shows that the nine symptom-related attributes determined as relevant by PCA also appear to be sufficient to represent the three dimensions resulting from EFA, namely, Uneasiness, Visual Discomfort and Loss of Balance. The simplified version of the SSQ has the potential to be more efficiently used than the initial SSQ for 360° video by focusing on the questions that are most relevant for individuals, shortening the required testing time.

The test methods recommended by the International Telecommunication Union (ITU) for assessing 2D video quality are often used for evaluating omnidirectional / 360° videos. In this paper, we compare the performance of three different test methods, Absolute Category Rating (ACR), a modified version of ACR (M-ACR) with double presentation of the test stimulus, and DSIS (Double Stimulus Impairment Scale), based on the statistical reliability, assessment time and simulator sickness. Different settings were used for HEVC encoding of five 360° source videos of 10 s duration. Results indicate that DSIS is statistically more reliable with higher resolving power, followed by M-ACR and ACR. We found that simulator sickness increases with time, but can be reduced by taking breaks in-between the test sessions. The results for simulator sickness are compared across test methods and with similar tests conducted under different contextual conditions. We also recorded and analyzed the exploration behaviour of the users. Apart from the methodological findings, the test results provide insights into video quality for different resolution and encoding settings (“bitrate ladders”). These may be useful for choosing appropriate representations in the context of HTTP-based adaptive streaming in case of full-frame streaming.

In viewport-adaptive streaming of omnidirectional video, only the field of view is streamed in high quality. While this has significant benefits over streaming the entire 360 sphere, no standard test method for perceived quality and simulator sickness is available to evaluate the quality of experience (QoE) of such streaming approaches. QoE testing is important as tile-based viewport-adaptive streaming technologies are replacing classical approaches because of significant bandwidth savings and increase in viewing quality. In this work, we propose a testbed, a test method, as well as test metrics for QoE tests of viewport-adaptive streaming approaches. The proposed method is validated in two different test setups, using a specific tile-based streaming technology available in the market. The chosen input variables (videos sequences, resolution, bandwidth, and network round-trip delay) are tested for their statistical significance. We found that our test method is suitable for QoE testing of viewport-adaptive streaming technologies. We also found that simulator sickness scores increase with test duration, but that breaks between tests reduce this effect. With our systematic test approach, it is possible to compare metrics among different test setups. On the tested technology, we found that a typical network delay (47 ms) only has a minimal effect on the quality ratings. Furthermore, the magnitude of the network delay does not influence simulator sickness for the system we have tested.

Color-difference interpolation (CDI) has been a widely used technique for various color demosaicking methods. CDI-based methods perform interpolation in the color-difference domain assuming that the color-difference signal is a low-pass signal. Recently, a residual interpolation (RI) algorithm, which conducts interpolation in the residual domain, has been developed, and it assumes that the residual domain is flatter or smoother than the channel-difference domain. In this paper, we comprehensively show a frequency domain analysis of these assumptions and observe that it is image dependent and creates artifacts in the interpolated image. With this view, we propose an algorithm that uses the inter-color correlation as well as the residual smoothness among the different channel much better than the existing algorithms. Experimental results emphasize that the proposed algorithm atribute better performances the existing algorithms in terms of both visual and objective quality.

QoE for omnidirectional videos comprises additional components such as simulator sickness and presence. In this paper, a series of tests is presented comparing different test protocols to assess integral quality, simulator sickness and presence for omnidirectional videos in one test run, using the HTC Vive Pro as head-mounted display. For quality ratings, the five-point ACR scale was used. In addition, the well-established Simulator Sickness Questionnaire and Presence Questionnaire methods were used, once in a full version, and once with only one single integral scale, to analyze how well presence and simulator sickness can be captured using only a single scale.

In this paper, we present a viewing test with 48 subjects watching 20 different entertaining omnidirectional videos on an HTC Vive Head Mounted Display (HMD) in a task-free scenario. While the subjects were watching the contents, we recorded their head movements. The obtained dataset is publicly available in addition to the links and timestamps of the source contents used. Within this study, subjects were also asked to fill in the Simulator Sickness Questionnaire (SSQ) after every viewing session. Within this paper, at first SSQ results are presented. Several methods for evaluating head rotation data are presented and discussed. In the course of the study, the collected dataset is published along with the scripts for evaluating the head rotation data. The paper presents the general angular ranges of the subjects' exploration behavior as well as an analysis of the areas where most of the time was spent. The collected information can be presented as head-saliency maps, too. In case of videos, head-saliency data can be used for training saliency models, as information for evaluating decisions during content creation, or as part of streaming solutions for region-of-interest-specific coding as with the latest tile-based streaming solutions, as discussed also in standardization bodies such as MPEG.

In this paper, we evaluated and compared the integral quality of different omnidirectional contents for two head mounted displays (HMDs), namely HTC Vive and Oculus Rift. We also investigated motion sickness and head-movements. To this aim, we categorized omnidirectional contents into three categories based on the degree of motion: high, medium and low motion. For assessing simulator sickness, we used the Simulator Sickness Questionnaire for each of the contents in both HMDs. The viewing direction for subjects while watching the contents were recorded in terms of the three coordinates yaw, roll and pitch. Experimental results show that HTC Vive offers better integral quality compared to Oculus Rift. We also compared simulator sickness scores along with the behavioral data for different contents and HMDs and discussed the results in the paper.

In this paper, we propose a prediction algorithm that uses adaptive predictor structures for lossless video coding. The proposed encoder finds cross-correlation coefficient (Rxy) between current frame and motion compensated previous frame and classifies the coefficient value into a small number of bins. For general videos, we propose four bins and associate different predictor structures with each of the bins. Similarly for medical videos, numbers of bins are three and each of these bins is associated with different predictor structures.