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Publicações

Publicações por Miguel Correia Melo

2016

Adaptation and Validation of the Igroup Presence Questionnaire (IPQ) in a Portuguese Sample

Autores
Vasconcelos Raposo, J; Bessa, M; Melo, M; Barbosa, L; Rodrigues, R; Teixeira, CM; Cabral, L; Sousa, AA;

Publicação
PRESENCE-TELEOPERATORS AND VIRTUAL ENVIRONMENTS

Abstract
The present study aims (a) to translate and adapt the Igroup Presence Questionnaire (IPQ) to the Portuguese context (semantic equivalence/ conceptual and content validity) and (b) to examine its psychometric properties (reliability and factorial validity). The sample consisted of 478 subjects (285 males and 193 females). The fidelity of the factors varied between 0.53 and 0.83. The confirmatory factor analysis results produced a 14-item version of IPQ-PT, accepting covariance between residual errors of some items of the instrument, as the best structural representation of the data analyzed. The CFA was conducted based on a three-variable model. The fit indexes obtained were X-2/df = 2.647, GFI = .948, CFI = .941, RSMEA = .059, and AIC = 254. These values demonstrate that the proposed Portuguese translation of the IPQ maintains its original validity, demonstrating it to be a robust questionnaire to measure the sense of presence in virtual reality studies. It is therefore recommended for use in presence research when using Portuguese samples.

2016

Does 3D 360 video enhance user's VR experience?: An Evaluation Study

Autores
Bessa, Maximino; Melo, Miguel; Narciso, David; Barbosa, Luis; Raposo, JoseVasconcelos;

Publicação
Proceedings of the XVII International Conference on Human Computer Interaction, Interacción 2016, Salamanca, Spain, September 13 - 16, 2016

Abstract
Technology for virtual reality has evolved at a fast pace and so is its affordability. Equipment such as head-mounted displays are now available for the average consumer at reasonable prices and this potentiates the use of contents such as video 360 in a more natural way. The purpose of this study was to measure the sense of presence and cybersickness comparing subjects by gender while experiencing a virtual reality application composed by type of VIDEO (360 video and 3D 360 video) using an head-mounted display. A Portuguese version of the Igroup Presence Questionnaire (IPQ) was used together with the Simulator Sickness Questionnaire (SSQ). The results have revealed that there are no significant differences across 2D and 3D videos in the sense of presence or cybersickness. © 2016 ACM.

2016

HDR video on mobile devices Unlocker of new opportunities for digital business

Autores
Melo, M; Barbosa, L; Meira, C; Branco, F; Bessa, M;

Publicação
2016 11TH IBERIAN CONFERENCE ON INFORMATION SYSTEMS AND TECHNOLOGIES (CISTI)

Abstract
Prior to having available the High Dynamic Range (HDR) techniques, certain levels of luminance could only by captured by the human eye. Currently, HDR technology overcomes the limitations of conventional imaging technology (also referred as Low Dynamic Range or LDR) and allows the capture and delivery of contents that can match the dynamic range of the real world. However, the state of the art of HDR video focus mainly on conventional sized displays typical of TVs or PCs. As the usage of mobile devices for multimedia consumption is increasing considerably, there is a need for studying the impact of the viewing of HDR video on such devices. This will allow to take full advantage of HDR technology, creating a set of opportunities for the digital business as it allows, among others, the presentation of products in a much more efficient and captivating way. On this paper it is presented a study that evaluates the impact of the HDR video delivery on mobile devices and compares it with the impact of Low Dynamic Range (LDR) content. Results show that the delivery of HDR video on mobiles is possible without requiring much more resources when comparing the delivery of LDR video.

2015

Information system for the management and visualization of multisensorial contents

Autores
Freitas, J; Meira, C; Melo, M; Barbosa, L; Bessa, M;

Publicação
PROCEEDINGS OF THE 2015 10TH IBERIAN CONFERENCE ON INFORMATION SYSTEMS AND TECHNOLOGIES (CISTI 2015)

Abstract
Humans sense the surrounding environment through five senses: sight, hearing, taste, smell and touch. This is valid not only for real life but also when one is exposed to virtual environments. It already exists systems that exploit the sensorial stimulation of more than one sense, however there are no available low-cost solutions that allow creative professionals to create and visualize multisensory contents. On this paper it is presented a solution for the creation and delivery of multisensory contents that allow users to create their own multisensory experiments. An evaluation of the developed solution that shows the potential of these new contents is also described.

2016

Presence in Virtual Environments: Objective Metrics vs. Subjective Metrics - A Pilot Study

Autores
Melo, M; Rocha, T; Barbosa, L; Bessa, M;

Publicação
2016 23RD PORTUGUESE MEETING ON COMPUTER GRAPHICS AND INTERACTION (EPCGI)

Abstract
The sense of presence and cybersickness are keyfactors to have into account when referring to Virtual Environments (VE). To achieve high levels of presence and minimize cybersickness, it is important to ensure that the user's stimulation is coherent with the contents that are being delivered. In this paper, it is presented a pilot study addressing the usage of both objective and subjective metrics to measure the sense of presence and cybersickness in VE in order to study possible correlations between these two evaluation approaches. On top of that, the pilot study includes two body positions to allow evaluating if the stimulation of the vestibular study has impact on the sense of presence and cybersickness. To evaluate presence and cybersickness, it was developed a VE that consists in a hill where participants ride a bicycle. To broaden the scope of the study, there were studied two body positions: standing and sitting on the bicycle. The equipment EMOTIV epoc+ was used to register the objective metrics. The subjective metrics were registered using the Igroup Presence Questionnaire (IPQ) and the Simulator Sickness Questionnaire (SSQ). To complement the collected data, the levels of fatigue and stress before and after the experience were also registered through self-evaluation. Results show that objective metrics Interest and Stress and the subjective metrics Realism, Fatigue and Stress have a positive interaction regarding the sense of presence. Results further suggest that there is a positive interaction between the objective metric Focus and the subjective metric Involvement.

2015

Screen reflections impact on HDR video tone mapping for mobile devices: an evaluation study

Autores
Melo, M; Bessa, M; Barbosa, L; Debattista, K; Chalmers, A;

Publicação
EURASIP JOURNAL ON IMAGE AND VIDEO PROCESSING

Abstract
This paper presents an evaluation of high-dynamic-range (HDR) video tone mapping on a small screen device (SSD) under reflections. Reflections are common on mobile devices as these devices are predominantly used on the go. With this evaluation, we study the impact of reflections on the screen and how different HDR video tone mapping operators (TMOs) perform under reflective conditions as well as understand if there is a need to develop a new or hybrid TMO that can deal with reflections better. Two well-known HDR video TMOs were evaluated in order to test their performance with and without on-screen reflections. Ninety participants were asked to rank the TMOs for a number of tone-mapped HDR video sequences on an SSD against a reference HDR display. The results show that the greater the area exposed to reflections, the larger the negative impact on a TMO's perceptual accuracy. The results also show that under observed conditions, when reflections are present, the hybrid TMOs do not perform better than the standard TMOs.

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