Quality of Experience Comparison of Stereoscopic 3D Videos in Different Projection Devices: Flat Screen, Panoramic Screen and Virtual Reality Headset

The use of Stereoscopic 3D (S3D) videos has been popular in commercial markets with ongoing developments in the field of visual entertainment in recent years. A wide variety of projection methods of 3D video content is currently available, such as projection to a panoramic screen and projection of omnidirectional video content from head mounted displays using Virtual Reality (VR) technology. This article investigates the Quality of Experience (QoE) and associated Visually Induced Motion Sickness (VIMS) caused by the viewing of S3D videos. The investigations used three different projection screens: a 3D flat screen, a 3D panoramic screen in a hemispherical shaped room and a VR headset. Several assessment methods including a Simulator Sickness Questionnaire (SSQ), ElectroEncephaloGraphy (EEG), and measurement tools for eye blink rate detection were applied to measure the QoE experienced by viewers. The SSQ scores were also compared with the behavioral data such as attention and meditation levels and enjoyment ratings acquired from different video content and projection screens. The results indicate that the projection screen is a key factor affecting the level of visual fatigue, VIMS and QoE assessments, which are discussed in-depth in the article

Remote Visual Observation of Real Places Through Virtual Reality Headsets

Virtual Reality has always represented a fascinating yet powerful opportunity that has attracted studies and technology developments, especially since the latest release on the market of powerful high-resolution and wide field-of-view VR headsets. While the great potential of such VR systems is common and accepted knowledge, issues remain related to how to design systems and setups capable of fully exploiting the latest hardware advances. The aim of the proposed research is to study and understand how to increase the perceived level of realism and sense of presence when remotely observing real places through VR headset displays. Hence, to produce a set of guidelines that give directions to system designers about how to optimize the display-camera setup to enhance performance, focusing on remote visual observation of real places. The outcome of this investigation represents unique knowledge that is believed to be very beneficial for better VR headset designs towards improved remote observation systems. To achieve the proposed goal, this thesis presents a thorough investigation of existing literature and previous researches, which is carried out systematically to identify the most important factors ruling realism, depth perception, comfort, and sense of presence in VR headset observation. Once identified, these factors are further discussed and assessed through a series of experiments and usability studies, based on a predefined set of research questions. More specifically, the role of familiarity with the observed place, the role of the environment characteristics shown to the viewer, and the role of the display used for the remote observation of the virtual environment are further investigated. To gain more insights, two usability studies are proposed with the aim of defining guidelines and best practices. The main outcomes from the two studies demonstrate that test users can experience an enhanced realistic observation when natural features, higher resolution displays, natural illumination, and high image contrast are used in Mobile VR. In terms of comfort, simple scene layouts and relaxing environments are considered ideal to reduce visual fatigue and eye strain. Furthermore, sense of presence increases when observed environments induce strong emotions, and depth perception improves in VR when several monocular cues such as lights and shadows are combined with binocular depth cues. Based on these results, this investigation then presents a focused evaluation on the outcomes and introduces an innovative eye-adapted High Dynamic Range (HDR) approach, which the author believes to be of great improvement in the context of remote observation when combined with eye-tracked VR headsets. Within this purpose, a third user study is proposed to compare static HDR and eye-adapted HDR observation in VR, to assess that the latter can improve realism, depth perception, sense of presence, and in certain cases even comfort. Results from this last study confirmed the author expectations, proving that eye-adapted HDR and eye tracking should be used to achieve best visual performances for remote observation in modern VR systems

Motion Parallax in Stereo 3D: Model and Applications

Binocular disparity is the main depth cue that makes stereoscopic images appear 3D. However, in many scenarios, the range of depth that can be reproduced by this cue is greatly limited and typically fixed due to constraints imposed by displays. For example, due to the low angular resolution of current automultiscopic screens, they can only reproduce a shallow depth range. In this work, we study the motion parallax cue, which is a relatively strong depth cue, and can be freely reproduced even on a 2D screen without any limits. We exploit the fact that in many practical scenarios, motion parallax provides sufficiently strong depth information that the presence of binocular depth cues can be reduced through aggressive disparity compression. To assess the strength of the effect we conduct psycho-visual experiments that measure the influence of motion parallax on depth perception and relate it to the depth resulting from binocular disparity. Based on the measurements, we propose a joint disparity-parallax computational model that predicts apparent depth resulting from both cues. We demonstrate how this model can be applied in the context of stereo and multiscopic image processing, and propose new disparity manipulation techniques, which first quantify depth obtained from motion parallax, and then adjust binocular disparity information accordingly. This allows us to manipulate the disparity signal according to the strength of motion parallax to improve the overall depth reproduction. This technique is validated in additional experiments

Stereoscopic 3D user interfaces : exploring the potentials and risks of 3D displays in cars

During recent years, rapid advancements in stereoscopic digital display technology has led to acceptance of high-quality 3D in the entertainment sector and even created enthusiasm towards the technology. The advent of autostereoscopic displays (i.e., glasses-free 3D) allows for introducing 3D technology into other application domains, including but not limited to mobile devices, public displays, and automotive user interfaces - the latter of which is at the focus of this work. Prior research demonstrates that 3D improves the visualization of complex structures and augments virtual environments. We envision its use to enhance the in-car user interface by structuring the presented information via depth. Thus, content that requires attention can be shown close to the user and distances, for example to other traffic participants, gain a direct mapping in 3D space

Biosignalų požymių regos diskomfortui vertinti išskyrimas ir tyrimas

Comfortable stereoscopic perception continues to be an essential area of research. The growing interest in virtual reality content and increasing market for head-mounted displays (HMDs) still cause issues of balancing depth perception and comfortable viewing. Stereoscopic views are stimulating binocular cues – one type of several available human visual depth cues which becomes conflicting cues when stereoscopic displays are used. Depth perception by binocular cues is based on matching of image features from one retina with corresponding features from the second retina. It is known that our eyes can tolerate small amounts of retinal defocus, which is also known as Depth of Focus. When magnitudes are larger, a problem of visual discomfort arises. The research object of the doctoral dissertation is a visual discomfort level. This work aimed at the objective evaluation of visual discomfort, based on physiological signals. Different levels of disparity and the number of details in stereoscopic views in some cases make it difficult to find the focus point for comfortable depth perception quickly. During this investigation, a tendency for differences in single sensor-based electroencephalographic EEG signal activity at specific frequencies was found. Additionally, changes in eye tracker collected gaze signals were also found. A dataset of EEG and gaze signal records from 28 control subjects was collected and used for further evaluation. The dissertation consists of an introduction, three chapters and general conclusions. The first chapter reveals the fundamental knowledge ways of measuring visual discomfort based on objective and subjective methods. In the second chapter theoretical research results are presented. This research was aimed to investigate methods which use physiological signals to detect changes on the level of sense of presence. Results of the experimental research are presented in the third chapter. This research aimed to find differences in collected physiological signals when a level of visual discomfort changes. An experiment with 28 control subjects was conducted to collect these signals. The results of the thesis were published in six scientific publications – three in peer-reviewed scientific papers, three in conference proceedings. Additionally, the results of the research were presented in 8 conferences.Dissertatio

Human factors in the perception of stereoscopic images

Research into stereoscopic displays is largely divided into how stereo 3D content looks, a field concerned with distortion, and how such content feels to the viewer, that is, comfort. However, seldom are these measures presented simultaneously. Both comfortable displays with unacceptable 3D and uncomfortable displays with great 3D are undesirable. These two scenarios can render conclusions based on research into these measures both moot and impractical. Furthermore, there is a consensus that more disparity correlates directly with greater viewer discomfort. These experiments, and the dissertation thereof, challenge this notion and argue for a more nuanced argument related to acquisition factors such as interaxial distance (IA) and post processing in the form of horizontal image translation (HIT). Indeed, this research seeks to measure tolerance limits for viewing comfort and perceptual distortions across different camera separations. In the experiments, HIT and IA were altered together. Following Banks et al. (2009), our stimuli were simple stereoscopic hinges, and we measured the perceived angle as a function of camera separation. We compared the predictions based on a ray-tracing model with the perceived 3D shape obtained psychophysically. Participants were asked to judge the angles of 250 hinges at different camera separations (IA and HIT remained linked across a 20 to 100mm range, but the angles ranged between 50° and 130°). In turn, comfort data was obtained using a five-point Likert scale for each trial. Stimuli were presented in orthoscopic conditions with screen and observer field of view (FOV) matched at 45°. The 3D hinge and experimental parameters were run across three distinct series of experiments. The first series involved replicating a typical laboratory scenario where screen position was unchanged (Experiment I), the other presenting scenarios representative of real-world applications for a single viewer (Experiments II, III, and IV), and the last presenting real-world applications for multiple viewers (Experiment V). While the laboratory scenario revealed greatest viewer comfort occurred when a virtual hinge was placed on the screen plane, the single-viewer experiment revealed into-the-screen stereo stimuli was judged flatter while out-of-screen content was perceived more veridically. The multi-viewer scenario revealed a marked decline in comfort for off-axis viewing, but no commensurate effect on distortion; importantly, hinge angles were judged as being the same regardless of off-axis viewing for angles of up to 45. More specifically, the main results are as follows. 1) Increased viewing distance enhances viewer comfort for stereoscopic perception. 2) The amount of disparity present was not correlated with comfort. Comfort is not correlated with angular distortion. 3) Distortion is affected by hinge placement on-screen. There is only a significant effect on comfort when the Camera Separation is at 60mm. 4) A perceptual bias between into the depth orientation of the screen stimuli, in to the screen stimuli were judged as flatter than out of the screen stimuli. 5) Perceived distortion not being affected by oblique viewing. Oblique viewing does not affect perceived comfort. In conclusion, the laboratory experiment highlights the limitations of extrapolating a controlled empirical stimulus into a less controlled “real world” environment. The typical usage scenarios consistently reveal no correlation between the amount of screen disparity (parallax) in the stimulus and the comfort rating. The final usage scenario reveals a perceptual constancy in off-axis viewer conditions for angles of up to 45, which, as reported, is not reflected by a typical ray-tracing model. Stereoscopic presentation with non-orthoscopic HIT may give comfortable 3D. However, there is good reason to believe that this 3D is not being perceived veridically. Comfortable 3D is often incorrectly converged due to the differences between distances specified by disparity and monocular cues. This conflict between monocular and stereo cues in the presentation of S3D content leads to loss of veridicality i.e. a perception of flatness. Therefore, correct HIT is recommended as the starting point for creating realistic and comfortable 3D, and this factor is shown by data to be far more important than limiting screen disparity (i.e. parallax). Based on these findings, this study proposes a predictive model of stereoscopic space for 3D content generators who require flexibility in acquisition parameters. This is important as there is no data for viewing conditions where the acquisition parameters are changed

A Comparative Emotions-detection Review for Non-intrusive Vision-Based Facial Expression Recognition

Affective computing advocates for the development of systems and devices that can recognize, interpret, process, and simulate human emotion. In computing, the field seeks to enhance the user experience by finding less intrusive automated solutions. However, initiatives in this area focus on solitary emotions that limit the scalability of the approaches. Further reviews conducted in this area have also focused on solitary emotions, presenting challenges to future researchers when adopting these recommendations. This review aims at highlighting gaps in the application areas of Facial Expression Recognition Techniques by conducting a comparative analysis of various emotion detection datasets, algorithms, and results provided in existing studies. The systematic review adopted the PRISMA model and analyzed eighty-three publications. Findings from the review show that different emotions call for different Facial Expression Recognition techniques, which should be analyzed when conducting Facial Expression Recognition. Keywords: Facial Expression Recognition, Emotion Detection, Image Processing, Computer Visio

Quality-controlled audio-visual depth in stereoscopic 3D media

BACKGROUND: The literature proposes several algorithms that produce “quality-controlled” stereoscopic depth in 3D films by limiting the stereoscopic depth to a defined depth budget. Like stereoscopic displays, spatial sound systems provide the listener with enhanced (auditory) depth cues, and are now commercially available in multiple forms. AIM: We investigate the implications of introducing auditory depth cues to quality-controlled 3D media, by asking: “Is it important to quality-control audio-visual depth by considering audio-visual interactions, when integrating stereoscopic display and spatial sound systems?” MOTIVATION: There are several reports in literature of such “audio-visual interactions”, in which visual and auditory perception influence each other. We seek to answer our research question by investigating whether these audio-visual interactions could extend the depth budget used in quality-controlled 3D media. METHOD/CONCLUSIONS: The related literature is reviewed before presenting four novel experiments that build upon each other’s conclusions. In the first experiment, we show that content created with a stereoscopic depth budget creates measurable positive changes in audiences’ attitude towards 3D films. These changes are repeatable for different locations, displays and content. In the second experiment we calibrate an audio-visual display system and use it to measure the minimum audible depth difference. Our data is used to formulate recommendations for content designers and systems engineers. These recommendations include the design of an auditory depth perception screening test. We then show that an auditory-visual stimulus with a nearer auditory depth is perceived as nearer. We measure the impact of this effect upon a relative depth judgement, and investigate how the impact varies with audio-visual depth separation. Finally, the size of the cross-modal bias in depth is measured, from which we conclude that sound does have the potential to extend the depth budget by a small, but perceivable, amount

Méthodes pour l'évaluation et la prédiction de la Qualité d'expérience, la préférence et l'inconfort visuel dans les applications multimédia. Focus sur la TV 3D stéréoscopique

Multimedia technology is aiming to improve people's viewing experience, seeking for better immersiveness and naturalness. The development of HDTV, 3DTV, and Ultra HDTV are recent illustrative examples of this trend. The Quality of Experience (QoE) in multimedia encompass multiple perceptual dimensions. For instance, in 3DTV, three primary dimensions have been identified in literature: image quality, depth quality and visual comfort. In this thesis, focusing on the 3DTV, two basic questions about QoE are studied. One is "how to subjectively assess QoE taking care of its multidimensional aspect?". The other is dedicated to one particular dimension, i.e., "what would induce visual discomfort and how to predict it?". In the first part, the challenges of the subjective assessment on QoE are introduced, and a possible solution called "Paired Comparison" is analyzed. To overcome drawbacks of Paired Comparison method, a new formalism based on a set of optimized paired comparison designs is proposed and evaluated by different subjective experiments. The test results verified efficiency and robustness of this new formalism. An application is the described focusing on the evaluation of the influence factor on 3D QoE. In the second part, the influence of 3D motion on visual discomfort is studied. An objective visual discomfort model is proposed. The model showed high correlation with the subjective data obtained through various experimental conditions. Finally, a physiological study on the relationship between visual discomfort and eye blinking rate is presented.La technologie multimédia vise à améliorer l'expérience visuelle des spectateurs, notamment sur le plan de l'immersion. Les développements récents de la TV HD, TV 3D, et TV Ultra HD s'inscrivent dans cette logique. La qualité d'expérience (QoE) multimédia implique plusieurs dimensions perceptuelles. Dans le cas particulier de la TV 3D stéréoscopique, trois dimensions primaires ont été identifiées dans la littérature: qualité d'image, qualité de la profondeur et confort visuel. Dans cette thèse, deux questions fondamentales sur la QoE sont étudiés. L'une a pour objet "comment évaluer subjectivement le caractère multidimensionnel de la QoE". L'autre s'intéresse à une dimension particuliére de QoE, "la mesure de l'inconfort et sa prédiction?". Dans la première partie, les difficultés de l'évaluation subjective de la QoE sont introduites, les mérites de méthodes de type "Comparaison par paire" (Paired Comparison en anglais) sont analysés. Compte tenu des inconvénients de la méthode de Comparaison par paires, un nouveau formalisme basé sur un ensemble de comparaisons par paires optimisées, est proposé. Celui-ci est évalué au travers de différentes expériences subjectives. Les résultats des tests confirment l'efficacité et la robustesse de ce formalisme. Un exemple d'application dans le cas de l'étude de l'évaluation des facteurs influençant la QoE est ensuite présenté. Dans la seconde partie, l'influence du mouvement tri-dimensionnel (3D) sur l'inconfort visuel est étudié. Un modèle objectif de l'inconfort visuel est proposé. Pour évaluer ce modèle, une expérience subjective de comparaison par paires a été conduite. Ce modèle de prédiction conduit à des corrélations élevées avec les données subjectives. Enfin, une étude sur des mesures physiologiques tentant de relier inconfort visuel et fréquence de clignements des yeux présentée