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Les techniques adaptatives de transmission vidéo s’appuient sur un contenu qui est encodé à différents niveaux de qualité et divisé en segments temporels. Avant de télécharger un segment, le client exécute un algorithme d’adaptation pour décider le meilleur niveau de qualité à considérer. Selon les services, ce niveau de qualité doit correspondre aux ressources réseaux disponibles, mais aussi à d’autres éléments comme le mouvement de tête d’un utilisateur regardant une vidéo immersive (à 360°) afin de maximiser la qualité de la portion de la vidéo qui est regardée. L’efficacité de l’algorithme d’adaptation a un impact direct sur la qualité de l’expérience finale. En cas de mauvaise sélection de segment, un client HTTP/1 doit attendre le téléchargement du prochain segment afin de choisir une qualité appropriée. Dans cette thèse, nous proposons d’utiliser le protocole HTTP/2 pour remédier à ce problème. Tout d’abord, nous nous focalisons sur le service de vidéo en direct. Nous concevons une stratégie de rejet d’images vidéo quand la bande passante est très variable afin d’éviter les arrêts fréquents de la lecture vidéo et l’accumulation des retards. Le client doit demander chaque image vidéo dans un flux HTTP/2 dédié pour contrôler la livraison des images par appel aux fonctionnalités HTTP/2 au niveau des flux concernées. Ensuite, nous optimisons la livraison des vidéos immersives en bénéficiant de l’amélioration de la prédiction des mouvements de têtes de l’utilisateur grâce aux fonctionnalités d’initialisation et de priorité de HTTP/2. Les résultats montrent que HTTP/2 permet d’optimiser l’utilisation des ressources réseaux et de s’adapter aux latences exigées par chaque service. / Adaptive video streaming techniques enable the delivery of content that is encoded at various levels of quality and split into temporal segments. Before downloading a segment, the client runs an adaptation algorithm to determine the level of quality that best matches the network resources. For immersive video streaming this adaptation mechanism should also consider the head movement of a user watching the 360° video to maximize the quality of the viewed portion. However, this adaptation may suffer from errors, which impact the end user’s quality of experience. In this case, an HTTP/1 client must wait for the download of the next segment to choose a suitable quality. In this thesis, we propose to use the HTTP/2 protocol instead to address this problem. First, we focus live streaming video. We design a strategy to discard video frames when the band width is very variable in order so as to avoid the rebuffering events and the accumulation of delays. The customer requests each video frame in an HTTP/2 stream which allows to control the delivery of frames by leveraging the HTTP/2 features at the level of the dedicated stream. Besides, we use the priority and reset stream features of HTTP/2 to optimize the delivery of immersive videos. We propose a strategy to benefit from the improvement of the user’s head movements prediction overtime. The results show that HTTP/2 allows to optimize the use of network resources and to adapt to the latencies required by each service.

[pt] Este trabalho disserta sobre características subjetivas e técnicas do Vídeo Imersivo (VI) e da Realidade Virtual 3D (3DVR). Observa, particularmente, aspectos de uma estratégia do design realista com que ambientes são concebidos e produzidos em projetos de Realidade Virtual (VR). O Uncanny Valley (UV) é um corolário do processo criativo de personagens, representado por uma curva conceitual em que a conexão emocional ou empatia entre audiência e personagens varia de forma não linear e não diretamente proporcional em função do realismo com que estes personagens são concebidos. Dado o protagonismo dos ambientes em projetos VR, haveria um Uncanny Valley of Places? Lugares, ambientes, espaços e a cenografia virtual estão sujeitos a uma estranheza em Realidade Virtual? Neste trabalho, são apresentados dados de três ciclos de pesquisa a partir três experimentos VR que buscam responder a estas questões: 1) O experimento Immersive Bike (IB), que integra estímulos visuais em VI com estímulos hapticos sinestésicos passivos; 2) A aplicação Rio 360 VR; aplicativo imersivo; 3) Pesquisa centrada no usuário, que compara diretamente aplicações VI e 3DVR. Este trabalho aponta caminhos para apoiar o processo criativo do Designer de Interação, demonstrando que sensação de imersão não é função direta do maior ou menor realismo com que as imagens são produzidas e sim é potencializada a partir da conexão multimodal do repertório de sensações dos usuários e sua conexão com as histórias propostas pelas aplicações imersivas. / [en] This dissertation aims to present subjective and technical characteristics of Immersive Video (IV) and 3D Virtual Reality (3DVR). Observes, particularly, aspects related to a realism approach design strategy for VR environment s conception. The Uncanny Valley (UV) is a corollary of illustrated character s creative process, a conceptual curve that represents the variation of the emotional connection with characters related to its realistic properties conception. The UV refers to the base of a parabolic positive curve of this dynamic relation between empathy and realism, on which is detected a weirdness or an uncanny as much realistic the character seams. Does VR environments are subjected to an analog UV? Is there an Uncanny Valley of Places? Do places, ambients, spaces and virtual scenography is subjected to an uncanny in Virtual Reality? This work presents results of three cycles of research based on three VR experiments that aim to respond these questions: 1) The Immersive Bike experiment, which design integrates IV with kinesthetic haptics; 2) Rio 360 VR0, an immersive aplication for mobile interaction; 3) Human-centered research that compares IV and 3DVR applications. This work points a path to the Interaction Designer creative process, proposing that the immersive sensation is not directly proportional of how realistic an immersive image is produced, but is potentiated by the multimodal user s connection with the storytelling of the immersive aplication.

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