A Subjective Quality Evaluation of 3D Mesh With Dynamic Level of Detail in Virtual Reality

Virtual reality (VR) videos, especially 360-degree VR videos, have attracted substantial research interests with the explosion of mobile VR devices in recent years. In this work, we propose a VR quality of experience (QoE) evaluation framework including online, offline and mixed scenarios that can meet the requirement of real applications. Under this framework, we further develop a subjective evaluation method and an objective QoE evaluation model based on network transmission parameters. A VR panoramic video database is established with nine different contents. This database contains 468 different samples coming from nine original contents. Then, in the subjective evaluation part, we propose to adopt four dimensions, i.e., quality score, immersion score, non-spinning sensation score and global score for the subjective evaluation purpose. These dimensions can meet the interaction and immersion features of the VR video service. In the objective evaluation part, an improved two-step neural network (INN) model is developed by using the features of the physiological psychology and cognitive neurology. This model captures the intrinsic link between the initial input network parameters and the final perception in VR transmission. Our results suggest that the proposed INN can achieve a higher pearson correlation coefficients than the other methods. Especially, it increases by 8.9% than the traditional NN method. Our work can make up for the shortage of traditional evaluation methods in term of the VR QoE subjective and objective evaluation in transmission scopes.

360-degree spherical images/videos, also called virtual reality (VR) images/videos, can provide an immersive experience of real scenes in some specific systems. This makes it widely used in VR games, sporting events and VR movies. However, due to its high resolution, it is so difficult to transmit, compress or store VR images/videos. Therefore, it is significant to study how noise affects the quality of VR images. To this end, this paper builds a VR video database, and carries out subjective and objective experiments on them. Specifically, first, six standard panoramic videos are processed by inputting three kinds of distorted types to establish a VR video database which comprises 96 videos. Second, we utilize the Double Stimulus Injury Scale (DSIS) for subjective experiments. All subjective scores are from 20 non-professional viewers. Third, we utilize 6 existing objective metrics to validate our database. Finally, experimental results demonstrate that the established VR database is suitable for subjective and objective quality evaluation of VR video. Our work has alleviated the problem of missing VR databases.

Effects of gymnasium envelope and daylight pattern on exercisers’ feedback in a virtual reality

With the development and advancement of Virtual Reality (VR) technology in recent years, hardware is no longer the main factor limiting VR into the public life, and the demand for user experience (UX) continues to increase. The development of VR is beginning to reveal a content-oriented trend. Whether the content is attractive enough will greatly affects users' experience and determine the service life of VR applications. Consequently, searching for interaction events that would affect VR UX is critical to improve user stickiness. At present, the researches on VR mainly focus on the improvement of hardware and software, and pay less attention to the content event design. Moreover, there is no unified and clear standard for VR UX evaluation. This paper attempts to find out the relationship between user traits, VR interaction events and user experience through realistic experiments. This paper firstly define four types of VR interaction events, and design a questionnaire for collecting the tester's traits and their subjective evaluation. During the experiment, objective physiological data of the testers and their participation process were recorded. The 80 testers were divided into two groups to experience two types of VR games with constant time. The statistical method and improved Prism algorithm were used to find out the correlation among user traits, type of game interaction events and user experience. The experiment results could provide references for VR designers and developers, and at the same time provide the preliminary study to standardized VR user experience evaluation.

In recent years, the application of virtual reality (VR) for spatial evaluation has gained traction in the fields of architecture and interior design. However, for VR to serve as a viable substitute for real-world environments, it is essential that experiences within VR elicit emotional responses comparable to those evoked by actual spaces. Despite this prerequisite, there remains a paucity of studies that objectively compare and evaluate the emotional responses elicited by VR and real-world environments. Consequently, it is not yet fully understood whether VR can reliably replicate the emotional experiences induced by physical spaces. This study aims to investigate the influence of presentation modality on emotional responses by comparing a VR space and a real-world space with identical designs. The comparison was conducted using both subjective evaluations (Semantic Differential method) and physiological indices (electroencephalography and heart rate variability). The results indicated that the real-world environment was associated with impressions of comfort and preference, whereas the VR environment evoked impressions characterized by heightened arousal. Additionally, elevated beta wave activity and increased beta/alpha ratios were observed in the VR condition, suggesting a state of high arousal, as further supported by positioning on the Emotion Map. Moreover, analysis of pNN50 revealed a transient increase in parasympathetic nervous activity during the VR experience. This study is positioned as a pilot investigation to explore physiological and emotional differences between VR and real spaces.

Many quality evaluation methods are used to assess uni-modal audio or video content without considering perceptual, cognitive, and interactive aspects present in virtual reality (VR) settings. Consequently, little is known regarding the repercussions of the employed evaluation method, content, and subject behavior on the quality ratings in VR. This mixed between- and within-subjects study uses four subjective audio quality evaluation methods (viz. multiple-stimulus with and without reference for direct scaling, and rank-order elimination and pairwise comparison for indirect scaling) to investigate the contributing factors present in multi-modal 6-DoF VR on quality ratings of real-time audio rendering. For each between-subjects employed method, two sets of conditions in five VR scenes were evaluated within-subjects. The conditions targeted relevant attributes for binaural audio reproduction using scenes with various amounts of user interactivity. Our results show all referenceless methods produce similar results using both condition sets. However, rank-order elimination proved to be the fastest method, required the least amount of repetitive motion, and yielded the highest discrimination between spatial conditions. Scene complexity was found to be a main effect within results, with behavioral and task load index results implying more complex scenes and interactive aspects of 6-DoF VR can impede quality judgments.

This paper presents a system and methodology for crowdsourcing subjective quality evaluations. The goal of this work is to study the feasibility of fast, inexpensive, and reliable subjective quality evaluations with crowdsourcing. We present a web-based system for conducting subjective quality evaluations using crowdsourcing platform. The results were evaluated by comparison with the formal subjective tests conducted by MPEG as a part of video standardization process. High quality compressed videos with known MOS values are used as references in subjective evaluations instead of the original lossless videos to address the bandwidth limitations. The results show that crowdsourcing can be a reliable platform for subjective quality evaluations.

Cloud virtual reality (VR) is an emerging solution for VR applications. This technology can significantly reduce the requirement of the high computational capacity of the VR terminal and is conducive to the promotion of virtual reality services. Accurately measuring user’s perceptual quality of cloud VR services is urgently demanded by VR service providers and network operators to further improve their quality of service. So far, there is still a lack of research about user’s perceptual quality of cloud VR services. In this paper, we conducted a subjective experiment to investigate the impact of frame rate on the perceptual quality of the artificial scene and captured real scene in cloud VR services. Experimental results reveal that different frame rates have different influence on users’ perceptual quality. Moreover, it is found that users’ perceptual quality for the artificial scene and the captured real scene do not have significant difference.

The 360-degree spherical images/videos, also called Virtual Reality (VR) images/videos, can provide immersive experience of the real-world scenes in some specific systems. This makes it widely employed in concerts/sports events live and VR movies. However, it is difficult to transport, compress or store VR images/videos due to their high resolution. So it is significant to research how the popular coding technologies influence the quality of VR images. To this aim, this paper carries out subjective quality evaluation of compressed VR images and examines the correlation performance of popular objective quality measures in accordance with the aforesaid subjective ratings. We first establish a Compressed VR Image Quality Database (CVIQD), which includes five source VR images and associated 165 compressed images under three prevailing coding technologies. The Single-Stimulus (SS) method is exploited to collect the subjective scores from 20 inexperienced viewers. Next, we implement 10 classical and recent objective quality metrics on the CVIQD database and compute the correlation between each above quality metric and subjective assessment in terms of five commonly used performance indices. Experimental results reveal that multi-scale based MS-SSIM and ADD-SSIM models have lead to high correlation with human visual perception.

With the maturity of virtual reality (VR) technology, people have been able to acquire virtual reality experience lightly. To discover more appropriate encoder for panoramic video encoding with the aim of ameliorating the quality of virtual reality video experience, this paper conducts the experiments of subjective and objective quality assessment of panoramic videos. First, sixteen standard panoramic videos are processed by using three encoders and inputting noise to set up a panoramic video database which comprises 384 videos. Second, in term of appraising several subjective methods and proposing a novel subjective methodology, subjective quality evaluation test on all panoramic video sequences' perception is conducted. Finally, this paper exhibits the objective experimental results using the existing objective metrics, and the performance of these metrics are evaluated according to the subjective test data, with the aim of discovering a superior objective metric to evaluate encoder for panoramic videos.

Objectives - to evaluate the latent period of complex sensory-motor reaction ^SMR) to relevant visual stimuli in virtual reality (VR) with personalized and indifferent content. Material and methods. The study included 10 healthy right-handed males aged 18-19. The selection of subjects in groups was based on two VR scenarios, the content of which reflected (personalized VR) or did not reflect their personal experience (indifferent VR). The latent period of CSMR to relevant visual stimuli was registered using a gamepad and an EEG recording system (BP-010302 BrainAmp Standart 128) in the oddball paradigm. VR scenarios were demonstrated using Oculus Rift CV1 headset. Registration of СSMR in personalized and indifferent VRs was done in three sessions with the interval of 24 hours. Each session lasted 7-8 minutes and included 30-40 CSMR registrations. Igroup Presence Questionnaire (IPQ) was used for subjective evaluation of VR immersiveness. The collected data was processed with IBM SPSS Statistics 22 software. Results. Statistically significant correlations were registered only in VR with personalized content, between the latent time of CSMR and indexes of spatial presence (0.694522) and a general effect of VR immersiveness (-0.592243). It was noted that latent period of CSMR to relevant visual stimuli in VR is determined by the semantic content: the time of CSMR to relevant stimuli in personalized VR was significantly less, than to those in indifferent VR. Conclusion. We support the adequacy of the methodology of studying the mechanisms of human voluntary attention with inclusion of personalized scenes in VR content. It is suggested that such methodology is promising for neurorehabilitation of patients with age-related cognitive impairment

Omnidirectional images and videos can provide immersive experience of real-world scenes in Virtual Reality (VR) environment. We present a perceptual omnidirectional image quality assessment (IQA) study in this paper since it is extremely important to provide a good quality of experience under the VR environment. We first establish an omnidirectional IQA (OIQA) database, which includes 16 source images and 320 distorted images degraded by 4 commonly encountered distortion types, namely JPEG compression, JPEG2000 compression, Gaussian blur and Gaussian noise. Then a subjective quality evaluation study is conducted on the OIQA database in the VR environment. Considering that humans can only see a part of the scene at one movement in the VR environment, visual attention becomes extremely important. Thus we also track head and eye movement data during the quality rating experiments. The original and distorted omnidirectional images, subjective quality ratings, and the head and eye movement data together constitute the OIQA database. State-of-the-art full-reference (FR) IQA measures are tested on the OIQA database, and some new observations different from traditional IQA are made. The OIQA database will be released to facilitate further research.

Correlations between subjective quality and physicochemical attributes of fresh fruits and vegetables

Cybersickness (CS) is an affliction that limits the use of virtual reality (VR) applications. For decades, the measurement of cybersickness has presented one of the most challenges that have aroused the interest of VR research community. Having strong effects on users’ health, cybersickness causes several symptoms relating to different factors. In most cases, the literature studies for VR cybersickness evaluation adopt the questionnaire-based approaches. Some studies have focused on physiological and postural instability-based approaches, while others support the VR content. Despite the attention paid to define measurements for assessing cybersickness, there is still a need for a more complete evaluation model that allows measuring cybersickness in real time. This paper defines a conceptual model that integrates subjective and objective evaluation of CS in real time. The proposed model considers three CS factors (i.e. individual, software and hardware). The aim is to consider the heterogeneous findings (subjective and objective measures) related to the selected CS factors that define integrated indicators. The theoretical part of the model was initially validated by researchers who have comprehensive knowledge and skills in VR domain. As a research perspective, we intend to evaluate the proposed model through a practical case study.

Quality assessment of acoustic environment reproduction methods for cinematic virtual reality in soundscape applications