Abstract In order to create immersive experiences in virtual worlds, we need to explore different human senses (sight, hearing, smell, taste, and touch). Many different devices have been developed by both industry and academia towards this aim. In this paper, we focus our attention on the researched area of thermal and wind devices to deliver the sensations of heat and cold against people’s skin and their application to human-computer interaction (HCI). First, we present a review of devices and their features that were identified as relevant. Then, we highlight the users’ experience with thermal and wind devices, highlighting limitations either found or inferred by the authors and studies selected for this survey. Accordingly, from the current literature, we can infer that, in wind and temperature-based haptic systems (i) users experience wind effects produced by fans that move air molecules at room temperature, and (ii) there is no integration of thermal components to devices intended for the production of both cold or hot airflows. Subsequently, an analysis of why thermal wind devices have not been devised yet is undertaken, highlighting the challenges of creating such devices.

Omnidirectional videos have become a leading multimedia format for Virtual Reality applications. While live 360$^\circ$videos offer a unique immersive experience, streaming of omnidirectional content at high resolutions is not always feasible in bandwidth-limited networks. While in the case of flat videos, scaling to lower resolutions works well, 360$^\circ$video quality is seriously degraded because of the viewing distances involved in head-mounted displays. Hence, in this article, we investigate first how quality degradation impacts the sense of presence in immersive Virtual Reality applications. Then, we are pushing the boundaries of 360$^\circ$technology through the enhancement with multisensory stimuli. 48 participants experimented both 360$^\circ$scenarios (with and without multisensory content), while they were divided randomly between four conditions characterised by different encoding qualities (HD, FullHD, 2.5K, 4K). The results showed that presence is not mediated by streaming at a higher bitrate. The trend we identified revealed however that presence is positively and significantly impacted by the enhancement with multisensory content. This shows that multisensory technology is crucial in creating more immersive experiences.

Using olfactory media to enhance traditional multimedia content opens up novel opportunities for user interactions. Whilst the influence of olfaction on user experience in mulsemedia (multiple sensorial media) environments has been previously studied, the impact of the fundamental dimensions of scent intensity and valence (odor hedonic dimension or pleasantness) have been largely unexplored. This is precisely what we target in this paper, which reports the results of an empirical investigation examining how scent intensity and valence impact mulsemedia Quality of Experience (QoE). Accordingly, 54 participants were exposed to different odor valences and scent intensity levels when viewing three short multimedia clips. In particular, we examine both subjective (self-reported) as well as objective QoE metrics, as evidenced by user heart rates and eye gaze patterns. Results show that whilst eye gaze patterns are largely unaffected by the experimental conditions, valence does have a statistically significant impact upon user heart rates, as does intensity for two of the three clips employed in our study. In terms of subjective QoE, results indicate that hedonic valence impacts on the sense of reality and enjoyment; however varying odor intensity levels do not seem to differentially impact on user experience, bringing into question the need for strong scent intensities.

Abstract A great deal of research effort has been put in exploring crossmodal correspondences in the field of cognitive science which refer to the systematic associations frequently made between different sensory modalities (e.g. high pitch is matched with angular shapes). However, the possibilities cross-modality opens in the digital world have been relatively unexplored. Therefore, we consider that studying the plasticity and the effects of crossmodal correspondences in a mulsemedia setup can bring novel insights about improving the human-computer dialogue and experience. Mulsemedia refers to the combination of three or more senses to create immersive experiences. In our experiments, users were shown six video clips associated with certain visual features based on color, brightness, and shape. We examined if the pairing with crossmodal matching sound and the corresponding auto-generated haptic effect, and smell would lead to an enhanced user QoE. For this, we used an eye-tracking device as well as a heart rate monitor wristband to capture users’ eye gaze and heart rate whilst they were experiencing mulsemedia. After each video clip, we asked the users to complete an on-screen questionnaire with a set of questions related to smell, sound and haptic effects targeting their enjoyment and perception of the experiment. Accordingly, the eye gaze and heart rate results showed significant influence of the cross-modally mapped multisensorial effects on the users’ QoE. Our results highlight that when the olfactory content is crossmodally congruent with the visual content, the visual attention of the users seems shifted towards the correspondent visual feature. Crosmodally matched media is also shown to result in an enhanced QoE compared to a video only condition.

Sensory studies emerged as a significant influence upon Human Computer Interaction and traditional multimedia. Mulsemedia is an area that extends multimedia addressing issues of multisensorial response through the combination of at least three media, typically a non-traditional media with traditional audio-visual content. In this paper, we explore the concepts of Quality of Experience and crossmodal correspondences through a case study of different types of mulsemedia setups. The content is designed following principles of crossmodal correspondence between different sensory dimensions and delivered through olfactory, auditory and vibrotactile displays. The Quality of Experience is evaluated through both subjective (questionnaire) and objective means (eye gaze and heart rate). Results show that the auditory experience has an influence on the olfactory sensorial responses and lessens the perception of lingering odor. Heat maps of the eye gazes suggest that the crossmodality between olfactory and visual content leads to an increased visual attention on the factors of the employed crossmodal correspondence (e.g., color, brightness, shape).

Previous research has shown that adding multisensory media-mulsemedia-to traditional audiovisual content has a positive effect on user Quality of Experience (QoE). However, the QoE impact of employing mulsemedia in 360° videos has remained unexplored. Accordingly, in this paper, a QoE study for watching a 360° video-with and without multisensory effects-in a full free-viewpoint VR setting is presented. The parametric space we considered to influence the QoE consists of the encoding quality and the motion level of the transmitted media. To achieve our research aim, we propose a wearable VR system that provides multisensory enhancement of 360° videos. Then, we utilise its capabilities to systematically evaluate the effects of multisensory stimulation on perceived quality degradation for videos with different motion levels and encoding qualities. Our results make a strong case for the inclusion of multisensory effects in 360° videos, as they reveal that both user-perceived quality, as well as enjoyment, are significantly higher when mulsemedia (as opposed to traditional multimedia) is employed in this context. Moreover, these observations hold true independent of the underlying 360° video encoding quality-thus QoE can be significantly enhanced with a minimal impact on networking resources.

The use of multiple senses in interactive applications has become increasingly feasible due to the upsurge of commercial, off-the-shelf devices to produce sensory effects. Creating Multiple Sensorial Media (MulSeMedia) immersive systems requires understanding their digital ecosystem. Mulsemedia systems encompass a set of applications, and devices of different types assembled to communicate or express feelings from the virtual world to the real world. Despite existing standards, tools, and recent research devoted to them, there is still a lack of formal and explicit representation of what mulse-media is. Misconceptions could eventually lead to the construction of solutions that might not take into account reuse, integration, standardization, among other design features. In this paper, we propose to establish a common conceptualization about mulsemedia systems through a reference ontology, named MulseOnto, covering their main notions. To evaluate it, we applied ontology verification and validation techniques, including assessment by humans and a data-driven approach. The results showed that MulseOnto can be used as a consensual conceptual model for exploring the knowledge about the whole chain of mulsemedia systems.

Human perception is inherently multisensory involving sight, hearing, smell, touch, and taste. Mulsemedia systems include the combination of traditional media (text, image, video, and audio) with non-traditional ones that stimulate other senses beyond sight and hearing. Whilst work has been done on some user-centred aspects that the distribution of mulsemedia data raises, such as synchronisation, and jitter, this paper tackles complementary issues that temporality constraints pose on the distribution of mulsemedia effects. It aims at improving response time interval in networked event-based mulsemedia systems based upon prior findings in this context. Thus, we reshaped the communication strategy of an open distributed mulsemedia platform called PlaySEM to work more efficiently with other event-based applications, such as games, VR/AR software, and interactive applications, wishing to stimulate other senses to increase the immersion of users. Moreover, we added lightweight communication protocols in its interface to analyse whether they reduce network overhead. To carry out the experiment, we developed mock applications for different protocols to simulate an interactive application working with the PlaySEM, measuring the delay between them. The results showed that by pre-processing sensory effects metadata before real-time communication, and selecting the appropriate protocol, response time interval in networked event-based mulsemedia systems can decrease remarkably.

Mulsemedia applications have become increasingly popular. There have been many efforts to increase the Quality of Experience (QoE) of users by using them. From the users' perspective, it is crucial that systems produce high levels of enjoyment and utility. Thus, many experimental tools have been developed and applied to different purposes such as entertainment, health, and culture. Despite that, little attention is paid to the evaluation of mulsemedia tools and platforms. In this paper, we present a time evaluation of the integration between a distributed mulsemedia platform called PlaySEM and an interactive application whereby users interact by gestures, in order to discover how long this process takes. We describe the test scenario and our approach for measuring this integration. Then, we discuss the results and point out aspects that bring implications to be taken into account for future similar solutions. The results showed values in the range of 27ms to 67ms on average spent throughout the process before the effective activation of the sensory effect devices on a wired network.

The paper presents an event driven approach for building interactive environments with sensory effects (such as RGB color light, wind and vibration) described through MPEGV standard. The most important differences of this work from previous ones are: (1) it divides the design process into well defined stages, showing the behavior of the system under a new perspective and their interactions, (2) it follows an event driven paradigm instead of a timeline one to send commands to sensory devices and (3) it decouples rendering of MPEG-V effects from the presentation software component. The method to validate the proposed approach was a case study, which has integrated multiples sensory effects to an interactive environment based on gesture recognizing.