15 research outputs found

    Importance of selecting research stimuli: a comparative study of the properties, structure and validity of both standard and novel emotion elicitation techniques

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    The principal aim of this doctoral research has been to investigate whether various popular methods of emotion elicitation perform differently in terms of self-reported participant affect - and if so, whether any of them is better able to mimic real-life emotional situations. A secondary goal has been to understand how continuous affect can be classified into discrete categories - whether by using clustering algorithms, or resorting to human participants for creating the classifications. A variety of research directions subserved these main goals: firstly, developing data-driven strategies for selecting 'appropriate' stimuli, and matching them across various stimulus modalities (i.e., words, sounds, images,films and virtual environments / VEs); secondly, comparing the chosen modalities on various self-report measures (with VEs assessed both with and without a head-mounted display / HMD); thirdly, comparing how humans classify emotional information vs. a clustering algorithm; and finally, comparing all five lab-based stimulus modalities to emotional data collected via an experience sampling phone app. Findings / outputs discussed will include a matched database of stimuli geared towards lab use, how the choice of stimulus modality may affect research results, the links (or discrepancies) between human and machine classification of emotional information, as well as range restriction affecting lab stimuli relative to `real-life' emotional phenomena

    The Impact of Multichannel Game Audio on the Quality of Player Experience and In-game Performance

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    Multichannel audio is a term used in reference to a collection of techniques designed to present sound to a listener from all directions. This can be done either over a collection of loudspeakers surrounding the listener, or over a pair of headphones by virtualising sound sources at specific positions. The most popular commercial example is surround-sound, a technique whereby sounds that make up an auditory scene are divided among a defined group of audio channels and played back over an array of loudspeakers. Interactive video games are well suited to this kind of audio presentation, due to the way in which in-game sounds react dynamically to player actions. Employing multichannel game audio gives the potential of immersive and enveloping soundscapes whilst also adding possible tactical advantages. However, it is unclear as to whether these factors actually impact a player’s overall experience. There is a general consensus in the wider gaming community that surround-sound audio is beneficial for gameplay but there is very little academic work to back this up. It is therefore important to investigate empirically how players react to multichannel game audio, and hence the main motivation for this thesis. The aim was to find if a surround-sound system can outperform other systems with fewer audio channels (like mono and stereo). This was done by performing listening tests that assessed the perceived spatial sound quality and preferences towards some commonly used multichannel systems for game audio playback over both loudspeakers and headphones. There was also a focus on how multichannel audio might influence the success of a player in a game, based on their in-game score and their navigation within a virtual world. Results suggest that surround-sound game audio is preferable over more regularly used two-channel stereo systems, because it is perceived to have higher spatial sound quality and there is an improvement in player performance. This illustrates the potential for multichannel game audio as a tool to positively influence player experiences, a core goal many game designers strive to achieve

    No-Reference Video Quality Assessment Model for Distortion Caused by Packet Loss in the Real-Time Mobile Video Services

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    Packet loss will make severe errors due to the corruption of related video data. For most video streams, because the predictive coding structures are employed, the transmission errors in one frame will not only cause decoding failure of itself at the receiver side, but also propagate to its subsequent frames along the motion prediction path, which will bring a significant degradation of end-to-end video quality. To quantify the effects of packet loss on video quality, a no-reference objective quality assessment model is presented in this paper. Considering the fact that the degradation of video quality significantly relies on the video content, the temporal complexity is estimated to reflect the varying characteristic of video content, using the macroblocks with different motion activities in each frame. Then, the quality of the frame affected by the reference frame loss, by error propagation, or by both of them is evaluated, respectively. Utilizing a two-level temporal pooling scheme, the video quality is finally obtained. Extensive experimental results show that the video quality estimated by the proposed method matches well with the subjective quality

    Improved online services by personalized recommendations and optimal quality of experience parameters

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    Indicator Of Experince For Mobile Data Networks

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    Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2013Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2013Bu çalışmada mobil veri şebekeleri için kullanıcıların yaşadıkları deneyim kalitesini ölçmek adına farklı bir metod önerilmektedir. Literatürde önerilen yöntemler ağırlıklı olarak kullanıcıların deneyimlerine ilişkin görüşlerinin anketler düzenlenerek alınması veya mobil cihazlara yerleştirilen akıllı yazılımlar ile deneyimlerin ölçülmesi şeklindedir. Bu sebeple yapılan çalışmalar örnek küme üzerinden deneyimin bütüne aitmiş gibi konumlandırılması esasına dayanmaktadır. Bu çalışmada bahsedilen yöntemlerden farklı olarak mobil şebekede bulunan sistemsel istatistiklerin kullanılması ve radyo şebekesinin deneyime etkisini hesaplayan bir modelin önerilmesiyle farklı bir hesaplama yöntemi önerilmektedir. Bu sayede sadece belli bir örnek küme değil, servisi deneyimleyen tüm kullanıcılar için bir sonuç elde etmek mümkün olmaktadır. Bu amaçla IoE kısaltması adı altında mobil veri servisleri kullanımlarında deneyimin başarısı ölçülebilir ve hesaplanabilir bir parametre ile ifade edilmiştir.In this study, introducing a new way of quality of experience calculation methodology is aimed. A new parameter, indicator of experience (IoE) has been introduced, which is a combination of quantised throughput and acceptability of the user for mobile internet service. Most QoE calculations use mobile client or user perception researches. Differently, network level statistics and radio network modeling is used to calculate IoE. This new approach is then compared with mobile client measurements in order to prove the usability of the approach.Yüksek LisansM.Sc

    Reliable Multicast transport of the video over the WiFi network

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    Le transport multicast est une solution efficace pour envoyer le même contenu à plusieurs récepteurs en même temps. Ce mode est principalement utilisé pour fournir des flux multimédia en temps réel. Cependant, le multicast classique de l IEEE 802.11 n'utilise aucun mécanisme d acquittement. Ainsi, l échec de réception implique la perte définitive du paquet. Cela limite la fiabilité du transport multicast et impact la qualité des applications vidéo. Pour résoudre ce problème, 802.11v et 802.11aa sont définis récemment. Le premier amendement propose Direct Multicast Service (DMS). D'autre part, le 802.11aa introduit GroupCast with Retries (GCR). GCR définit deux nouvelles politiques de retransmission : Block Ack (BACK) et Unsolicited Retry (UR).Dans cette thèse, nous évaluons et comparons les performances de 802.11v/aa. Nos résultats montrent que tous les nouveaux protocoles multicast génèrent un overhead de transmission important. En outre, DMS a une scalabilité très limitée, et GCR-BACK n'est pas approprié pour des grands groupes multicast. D autre part, nous montrons que DMS et GCR-BACK génèrent des latences de transmission importantes lorsque le nombre de récepteurs augmente. Par ailleurs, nous étudions les facteurs de pertes dans les réseaux sans fil. Nous montrons que l'indisponibilité du récepteur peut être la cause principale des pertes importantes et de leur nature en rafales. En particulier, nos résultats montrent que la surcharge du processeur peut provoquer un taux de perte de 100%, et que le pourcentage de livraison peut être limité à 35% lorsque la carte 802.11 est en mode d économie d'énergie.Pour éviter les collisions et améliorer la fiabilité du transport multicast, nous définissons le mécanisme Busy Symbol (BS). Nos résultats montrent que BS évite les collisions et assure un taux de succès de transmission très important. Afin d'améliorer davantage la fiabilité du trafic multicast, nous définissons un nouveau protocole multicast, appelé Block Negative Acknowledgement (BNAK). Ce protocole opère comme suit. L AP envoi un bloc de paquets suivi par un Block NAK Request (BNR). Le BNR permet aux membres de détecter les données manquantes et d envoyer une demande de retransmission, c.à.d. un Block NAK Response (BNAK). Un BNAK est transmis en utilisant la procédure classique d accès au canal afin d'éviter toute collision avec d'autres paquets. En plus, cette demande est acquittée. Sous l'hypothèse que 1) le récepteur est situé dans la zone de couverture du débit de transmission utilisé, 2) les collisions sont évitées et 3) le terminal a la bonne configuration, très peu de demandes de retransmission sont envoyées, et la bande passante est préservée. Nos résultats montrent que BNAK a une très grande scalabilité et génère des délais très limités. En outre, nous définissons un algorithme d'adaptation de débit pour BNAK. Nous montrons que le bon débit de transmission est sélectionné moyennant un overhead très réduit de moins de 1%. En plus, la conception de notre protocole supporte la diffusion scalable de lavvidéo. Cette caractéristique vise à résoudre la problématique de la fluctuation de la bande passante, et à prendre en considération l'hétérogénéité des récepteurs dans un réseau sans fil.The multicast transport is an efficient solution to deliver the same content to many receivers at the same time. This mode is mainly used to deliver real-time video streams. However, the conventional multicast transmissions of IEEE 802.11 do not use any feedback policy. Therefore missing packets are definitely lost. This limits the reliability of the multicast transport and impacts the quality of the video applications. To resolve this issue, the IEEE 802.11v/aa amendments have been defined recently. The former proposes the Direct Multicast Service (DMS). On the other hand, 802.11aa introduces Groupcast with Retries (GCR) service. GCR defines two retry policies: Block Ack (BACK) and Unsolicited Retry (UR).In this thesis we evaluate and compare the performance of 802.11v/aa. Our simulation results show that all the defined policies incur an important overhead. Besides, DMS has a very limited scalability, and GCR-BACK is not appropriate for large multicast groups. We show that both DMS and GCR-BACK incur important transmission latencies when the number of the multicast receivers increases. Furthermore, we investigate the loss factors in wireless networks. We show that the device unavailability may be the principal cause of the important packet losses and their bursty nature. Particularly, our results show that the CPU overload may incur a loss rate of 100%, and that the delivery ratio may be limited to 35% when the device is in the power save mode.To avoid the collisions and to enhance the reliability of the multicast transmissions, we define the Busy Symbol (BS) mechanism. Our results show that BS prevents all the collisions and ensures a very high delivery ratio for the multicast packets. To further enhance the reliability of this traffic, we define the Block Negative Acknowledgement (BNAK) retry policy. Using our protocol, the AP transmits a block of multicast packets followed by a Block NAK Request (BNR). Upon reception of a BNR, a multicast member generates a Block NAK Response (BNAK) only if it missed some packets. A BNAK is transmitted after channel contention in order to avoid any eventual collision with other feedbacks, and is acknowledged. Under the assumption that 1) the receiver is located within the coverage area of the used data rate, 2) the collisions are avoided and 3) the terminal has the required configuration, few feedbacks are generated and the bandwidth is saved. Our results show that BNAK has a very high scalability and incurs very low delays. Furthermore, we define a rate adaptation scheme for BNAK. We show that the appropriate rate is selected on the expense of a very limited overhead of less than 1%. Besides, the conception of our protocol is defined to support the scalable video streaming. This capability intends to resolve the bandwidth fluctuation issue and to consider the device heterogeneity of the group members.BORDEAUX1-Bib.electronique (335229901) / SudocSudocFranceF

    A Study of the Structural Similarity Image Quality Measure with Applications to Image Processing

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    Since its introduction in 2004, the Structural Similarity (SSIM) index has gained widespread popularity as an image quality assessment measure. SSIM is currently recognized to be one of the most powerful methods of assessing the visual closeness of images. That being said, the Mean Squared Error (MSE), which performs very poorly from a perceptual point of view, still remains the most common optimization criterion in image processing applications because of its relative simplicity along with a number of other properties that are deemed important. In this thesis, some necessary tools to assist in the design of SSIM-optimal algorithms are developed. This work combines theoretical developments with experimental research and practical algorithms. The description of the mathematical properties of the SSIM index represents the principal theoretical achievement in this thesis. Indeed, it is demonstrated how the SSIM index can be transformed into a distance metric. Local convexity, quasi-convexity, symmetries and invariance properties are also proved. The study of the SSIM index is also generalized to a family of metrics called normalized (or M-relative) metrics. Various analytical techniques for different kinds of SSIM-based optimization are then devised. For example, the best approximation according to the SSIM is described for orthogonal and redundant basis sets. SSIM-geodesic paths with arclength parameterization are also traced between images. Finally, formulas for SSIM-optimal point estimators are obtained. On the experimental side of the research, the structural self-similarity of images is studied. This leads to the confirmation of the hypothesis that the main source of self-similarity of images lies in their regions of low variance. On the practical side, an implementation of local statistical tests on the image residual is proposed for the assessment of denoised images. Also, heuristic estimations of the SSIM index and the MSE are developed. The research performed in this thesis should lead to the development of state-of-the-art image denoising algorithms. A better comprehension of the mathematical properties of the SSIM index represents another step toward the replacement of the MSE with SSIM in image processing applications
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