Assessing the Zone of Comfort in Stereoscopic Displays using EEG

The conflict between vergence (eye movement) and accommodation (crystalline lens deformation) occurs in every stereoscopic display. It could cause important stress outside the "zone of comfort", when stereoscopic effect is too strong. This conflict has already been studied using questionnaires, during viewing sessions of several minutes. The present pilot study describes an experimental protocol which compares two different comfort conditions using electroencephalography (EEG) over short viewing sequences. Analyses showed significant differences both in event-related potentials (ERP) and in frequency bands power. An uncomfortable stereoscopy correlates with a weaker negative component and a delayed positive component in ERP. It also induces a power decrease in the alpha band and increases in theta and beta bands. With fast responses to stimuli, EEG is likely to enable the conception of adaptive systems, which could tune the stereoscopic experience according to each viewer

3D fatigue from stereoscopic 3D video displays: Comparing objective and subjective tests using electroencephalography

The use of stereoscopic display has increased in recent times, with a growing range of applications using 3D videos for visual entertainment, data visualization, and medical applications. However, stereoscopic 3D video can lead to adverse reactions amongst some viewers, including visual fatigue, headache and nausea; such reactions can further lead to Visually Induced Motion Sickness (VIMS). Whilst motion sickness symptoms can occur from other types of visual displays, this paper investigates the rapid adjustment triggered by human pupils as a potential cause of 3D fatigue due to VIMS from stereoscopic 3D displays. Using Electroencephalogram (EEG) biosignals and eye blink tools to measure the 3D fatigue, a series of objective and subjective experiments were conducted to investigate the effect of stereoscopic 3D across a series of video sequences

Psychophysiology-based QoE assessment : a survey

We present a survey of psychophysiology-based assessment for quality of experience (QoE) in advanced multimedia technologies. We provide a classification of methods relevant to QoE and describe related psychological processes, experimental design considerations, and signal analysis techniques. We summarize multimodal techniques and discuss several important aspects of psychophysiology-based QoE assessment, including the synergies with psychophysical assessment and the need for standardized experimental design. This survey is not considered to be exhaustive but serves as a guideline for those interested to further explore this emerging field of research

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

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

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

Evaluation of EEG-based Complementary Features for Assessment of Visual Discomfort based on Stable Depth Perception Time

The investigation aimed at the evaluation of EEG activity during stereoscopic perception of images with different levels of visual comfort. 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 our investigation, we found a tendency for differences in single sensor-based EEG signal activity at specific frequencies. A dataset of EEG signal records from 19 control subjects was collected and used for further evaluation. To support the reproducible research this dataset of EEG activity with associated subjective scores was made publicly available. During the experimental investigation, we found differences in EEG signal activity at different levels of visual comfort. In addition, the dynamics of EEG signal activity correlated to the moment of depth perception indication registered by the control subjects. The results of our investigation show that the ratio of alpha estimated from a single EEG sensor placed over the frontal lobe can serve as a complementary feature for the automatic detection of visually uncomfortable stereoscopic views