Iej Ingrid Heynderickx

Visual discomfort of 3D TV: Assessment methods and modeling

To gain knowledge on how visual discomfort is built up while watching stereoscopic content an experiment was designed with two objectives: (1) to compare the continuous evaluation method with other assessment methods that potentially can substitute the continuous evaluation for the assessment of visual discomfort of e.g., feature-length movies, and (2) to relate the impact of time-variant content characteristics, such as motion and disparity, to the assessment of visual discomfort. In an experiment a 24 min 3D movie ‘Spy Kids 3-D: game over’ converted from 2D to 3D was displayed on a 9-view autostereoscopic lenticular LCD, and continuously assessed in terms of visual comfort by 24 participants. Additional assessment methods included the assessment of six 10 s sequences captured from the 3D movie and a single retrospective assessment of the entire 3D movie. Time-variant content characteristics, such as derivatives of motion and screen disparity values, were extracted from the 3D movie with motion and depth estimation algorithms. The moment-to-moment values of these characteristics were correlated to the continuous assessment scores of visual discomfort. With respect to the first objective, results reveal that the correlation between the assessment of the 10 s sequences captured from the 3D movie and their corresponding part within the continuous assessment is low, whereas the correlation between the retrospective assessment and the mean of the continuous assessment score over scene parts with a high screen disparity is higher. With respect to the second objective, for static scenes the visual comfort can be largely described by the screen disparity offset and range. For dynamic scenes the visual comfort is largely related to the screen disparity range, lateral motion and to the change in screen disparity.

Comparative Study of Fixation Density Maps

Fixation density maps (FDM) created from eye tracking experiments are widely used in image processing applications. The FDM are assumed to be reliable ground truths of human visual attention and as such, one expects a high similarity between FDM created in different laboratories. So far, no studies have analyzed the degree of similarity between FDM from independent laboratories and the related impact on the applications. In this paper, we perform a thorough comparison of FDM from three independently conducted eye tracking experiments. We focus on the effect of presentation time and image content and evaluate the impact of the FDM differences on three applications: visual saliency modeling, image quality assessment, and image retargeting. It is shown that the FDM are very similar and that their impact on the applications is low. The individual experiment comparisons, however, are found to be significantly different, showing that inter-laboratory differences strongly depend on the experimental conditions of the laboratories. The FDM are publicly available to the research community.

The impact of video characteristics and subtitles on visual comfort of 3D TV

Some viewers of stereoscopic content experience visual discomfort that can be induced or intensified by certain video characteristics such as fast in-scene motion, large changes in disparity and depth discontinuities caused by subtitles. An experiment was carried out to determine the impact of these video characteristics in terms of visual comfort via different measurement methods. Two 3-D movies of approximately 15 min each, both with and without subtitles, were assessed in terms of visual comfort via a continuous assessment and retrospective questionnaires. Analysis of the questionnaire data revealed that subtitles negatively affect how viewers watch stereoscopic movie in terms of general visual comfort items as well as in terms of double vision and sharpness. Via the questionnaires, participants reported that their visual comfort assessment depended primarily on the motion and (changes in) depth in the video content. The scores of the continuous assessment were directly correlated to video characteristics that were derived from the 3-D movies. In line with the questionnaire results, analysis of the continuous assessment scores revealed that visual comfort could be predicted from a linear combination of these video characteristics per scene, yet more complex models are required to extend the comfort prediction to entire movies, incorporating different scenes.

Understanding the role of social context and user factors in video Quality of Experience

We examine the impact of social context on compressed video Quality of Experience.We analyze the effect on QoE of user factors such as interest and demographics.Co-viewing videos increases users enjoyment and endurability of the experience.Low bitrate does not decrease video enjoyment, yet lower video quality is perceived.User interest increases QoE; this effect is suppressed by the presence of co-viewers. Quality of Experience is a concept to reflect the level of satisfaction of a user with a multimedia content, service or system. So far, the objective (i.e., computational) approaches to measure QoE have been mostly based on the analysis of the media technical properties. However, recent studies have shown that this approach cannot sufficiently estimate user satisfaction, and that QoE depends on multiple factors, besides the media technical properties. This paper aims to identify the role of social context and user factors (such as interest and demographics) in determining quality of viewing experience. We also investigate the relationships between social context, user factors and some media technical properties, the effect of which on image quality is already known (i.e., bitrate level and video genre). Our results show that the presence of co-viewers increases the users level of enjoyment and enhances the endurability of the experience, and so does interest in the video content. Furthermore, although participants can clearly distinguish the various levels of video quality used in our study, these do not affect any of the other aspects of QoE. Finally, we report an impact of both gender and cultural background on QoE. Our results provide a first step toward building an accurate model of user QoE appreciation, to be deployed in future multimedia systems to optimize the user experience.

Conversations with a virtual human: Synthetic emotions and human responses

To test whether synthetic emotions expressed by a virtual human elicit positive or negative emotions in a human conversation partner and affect satisfaction towards the conversation, an experiment was conducted where the emotions of a virtual human were manipulated during both the listening and speaking phase of the dialogue. Twenty-four participants were recruited and were asked to have a real conversation with the virtual human on six different topics. For each topic the virtual human’s emotions in the listening and speaking phase were different, including positive, neutral and negative emotions. The results support our hypotheses that (1) negative compared to positive synthetic emotions expressed by a virtual human can elicit a more negative emotional state in a human conversation partner, (2) synthetic emotions expressed in the speaking phase have more impact on a human conversation partner than emotions expressed in the listening phase, (3) humans with less speaking confidence also experience a conversation with a virtual human as less positive, and (4) random positive or negative emotions of a virtual human have a negative effect on the satisfaction with the conversation. These findings have practical implications for the treatment of social anxiety as they allow therapists to control the anxiety evoking stimuli, i.e., the expressed emotion of a virtual human in a virtual reality exposure environment of a simulated conversation. In addition, these findings may be useful to other virtual applications that include conversations with a virtual human.

Influence of processing conditions on the anisotropy in injection-moulded thermotropic LCPs

Abstract The influence of injection-moulding conditions on the anisotropy in macroscopic properties of flat rectangular plates has been evaluated for a thermotropic main-chain liquid crystalline polymer. The anisotropic mechanical and thermal behaviour is correlated to the degree of molecular ordering as determined from X-ray diffraction. The geometry of the injection-moulded plates, such as their thickness and the thickness and shape of the sprue, as well as the injection speed, significantly affect the molecular ordering and the resulting anisotropy in, for example, Youngs modulus and heat conduction. The tendencies observed are explained in terms of molecular alignment as a consequence of the combination of shear, elongational fountain flow and the elongational deformation in the sprue.

An exploration of the initial effects of stereoscopic displays on optometric parameters

Citation information: Fortuin MF, Lambooij MT, IJsselsteijn WA, Heynderickx I, Edgar DF & Evans BJW. An exploration of the initial effects of stereoscopic displays on optometric parameters. Ophthalmic Physiol Opt 2011, 31, 33–44.

Molecular orientation in flat plates of liquid-crystalline polymer using low-cost reflectance Fourier-transform infra-red microscopy

Abstract The direction of the averaged molecular orientation as well as the order parameter in injection-moulded flat plates of liquid-crystalline polymer (Vectra A950, A530 and A130) were investigated by infra-red dichroism. The measurements were performed with a low-cost Fourier-transform infra-red reflectance microscope. Lateral and depth profiles, inclusive of three-dimensional imaging, of the molecular orientation were measured as a function of thickness of the flat plate and injection speed.

Inducing sadness and anxiousness through visual media: Measurement techniques and persistence

The persistence of negative moods (sadness and anxiousness) induced by three visual Mood Induction Procedures (MIP) was investigated. The evolution of the mood after the MIP was monitored for a period of 8 min with the Self-Assessment Manikin (SAM; every 2 min) and with recordings of skin conductance level (SCL) and electrocardiography (ECG). The SAM pleasure ratings showed that short and longer film fragments were effective in inducing a longer lasting negative mood, whereas the negative mood induced by the IAPS slideshow was short lived. The induced arousal during the anxious MIPs diminished quickly after the mood induction; nevertheless, the SCL data suggest longer lasting arousal effects for both movies. The decay of the induced mood follows a logarithmic function; diminishing quickly in the first minutes, thereafter returning slowly back to baseline. These results reveal that caution is needed when investigating the effects of the induced mood on a task or the effect of interventions on induced moods, because the induced mood diminishes quickly after the mood induction.

Lighting to make you feel better: Improving the mood of elderly people with affective ambiences

Current lighting technologies extend the options for changing the appearance of rooms and closed spaces, as such creating ambiences with an affective meaning. Using intelligence, these ambiences may instantly be adapted to the needs of the room’s occupant(s), possibly improving their well-being. We hypothesized that ambiences with a clearly recognizable, positive affective meaning could be used to effectively mitigate negative mood in elderly. After inducing a sad mood with a short movie one group of elderly was immersed in a positive high arousing (i.e., activating) ambience, and another group in a neutral ambience. Similarly, after inducing anxiety with a short movie one group of elderly was immersed in a pleasant low arousing (i.e., cozy) ambience, and another group in a neutral ambience. We monitored the evolution of the mood of the four groups of elderly over a period of ten minutes after the mood induction, with both self-reported mood measurements (every 2 minutes) and constant measurements of the skin conductance response (SCR) and electrocardiography (ECG). In line with our hypothesis we found that the activating ambience was physiologically more arousing than the neutral ambience. The cozy ambience was more effective in calming anxious elderly than the neutral ambience, as reflected by both the self-reported and physiological measurements.