A esteganografia em vídeos digitais possibilita o ocultamento de um grande volume de informações quando comparada a técnicas em imagens. Contudo, esta tarefa não é trivial quando aplicada a vídeos comprimidos, pois a inserção de informações ocultas pode adicionar ruído dificultando a perfeita recuperação das mesmas durante a decodificação. Este trabalho apresenta uma técnica para esteganografia em vídeos comprimidos, denominada MP4Stego, a qual explora estruturas e tecnologias do padrão de vídeo MPEG-4 de modo a proceder recuperação de informações sem perda e apresentar maior capacidade de inserção de dados ocultos. Entre os benefícios da técnica estão: A capacidade de ocultamento de grande volume de dados; a capacidade de reprodução do vídeo contendo dados ocultos em players não especializados (ajudando a dar a ilusão de que se trata de um vídeo comum), sua imunidade, até o momento, as técnicas de esteganálise / Digital video steganography makes possible to hide higher volumes of information than the broadly used image steganography techniques. However, apply steganography to compressed digital videos is not a trivial task because the information hiding process may add noise to the original data. In this way, during the video decoding, the recovered hidden information is not an exact copy of the original data. This work presents a new steganographic technique, called MP4Stego, which explores new video structures of the MPEG-4 standard in order to recover hidden data without loss and in order to provide higher capacity of hidden data insertion. Some benefits of the MP4Stego technique are: to hide high volumes of data; to playback steganographyed videos by the means of non specialized players (this helps users to think that it is a regular video); so far, its immunity to stegoanalysis techniques

O trabalho apresentado nesta dissertação trata do desenvolvimento de um mecanismo para adaptação automática de ví?deo MPEG-4 ao vivo, de modo a atender as necessidades ou capacidades atuais de usuários e do sistema. Um dos desafios dessa área é capturar e representar as informações necessárias para realizar a adaptação. Assim, utilizando técnicas da área de computação ciente de contexto, foi desenvolvido um modelo extensível para representação de dispositivos. Também foram desenvolvidos métodos automáticos e semi-automáticos para capturar as informações necessárias. Neste trabalho foi adotado o modelo de recodificação de vídeo, o qual pode gerar atrasos que inviabilizam a adaptação de vídeo ao vivo em aplicações interativas. Assim, este trabalho realizou uma avaliação do impacto causado pela recodificação no atraso total, fim-a-fim, percebido pelo usuário. / This work presents the development of a mechanism to automatically adapt MPEG-4 live video, in a way to response the actual necessities or capacities of users or systems. One of the challanges in this area is to capture and represent the information needed to adapting content. Thus, using context aware computing techniques, an extensible model has been developed, which can be used to represent devices. It has also been developed automatic and semi-automatic methods to capture the needed information. In this work, the transcoding model has been adopted, which may generate latency, making difficult to use transcoding with interactive applications. In this way, this work has evaluated the impact caused by the transcoding when compared to the end-to-end total delay perceived by the user.

La production de dessins animés 2D qui suit actuellement un schéma mis en place dans les années 1920 fait intervenir un très grand nombre de compétences humaines et de métiers différents. Par opposition à ce mode de travail traditionnel, la production de films de synthèse 3D, en exploitant les technologies et les outils les plus récents de modélisation et d'animation 3D, s'affranchit en bonne partie de cette composante artisanale et vient concurrencer l'industrie du dessin animé traditionnel en termes de temps et coûts de fabrication. <br />Les défis à relever par l'industrie du dessin animé 2D se posent donc en termes de :<br />1. Réutilisation des contenus selon le paradigme d'accès «Create once, render many»,<br />2. Facilité d'échange et de transmission des contenus ce qui nécessite de disposer d'un unique format de représentation,<br />3. Production efficace et économique des contenus requérant alors une animation automatisée par ordinateur.<br />Dans ce contexte compétitif, cette thèse, réalisée dans le cadre du projet industriel TOON financé par la société Quadraxis (www.quadraxis.com) et supporté par l'Agence Nationale de Valorisation de la Recherche (ANVAR), a pour objectif de contribuer au développement d'une plate-forme de reconstruction, déformation et animation de modèles 3D de visages pour les dessins animés 2D. Vecteurs de la parole et des expressions, les visages nécessitent en effet une attention particulière quant à leur modélisation et animation conforme aux souhaits des créateurs de dessins animés. <br />Un état de l'art des méthodes, outils et systèmes contribuant à la création de modèles 3D faciaux et à leur animation est présenté et discuté au regard des contraintes spécifiques qui régissent les règles de création des dessins animés 2D et la chaîne de fabrication traditionnelle.<br />Ayant identifié les verrous technologiques à lever, nos contributions ont porté sur :<br /> l'élaboration d'une méthode de conception de visages virtuels 3D à partir d'une part d'un modèle 3D de type seamless, adapté aux exigences d'animation sans rupture, et d'autre part d'un ensemble de dessins 2D représentant les caractéristiques faciales,<br /> la mise au point d'une procédure de création de poses clés, mettant en œuvre plusieurs méthodes de déformation non-rigide,<br /> la conception d'un module d'animation 3D compatible avec le standard MPEG-4/AFX. <br /><br />Les développements réalisés, intégrés dans un premier prototype de la plate-forme FaceTOON, montrent un gain en temps de 20% sur l'ensemble de la chaîne de production tout en assurant une complète interopérabilité des applications via le standard MPEG-4.

Avec le développement des réseaux informatiques, principalement d'Internet, il devient de plus en plus facile de développer des applications dont l'exécution est répartie entre un ordinateur local, le client, et un ordinateur à distance (à une autre extrémité du canal de transmission), le serveur. Les progrès techniques de ces dernières années au niveau matériel ont rendu possible l'affichage en 3D (jeux, navigation cartographique, mondes virtuels) sur les mobiles. Cependant, l'exécution de ces applications complexes sur le terminal client est impossible, à moins de réduire la qualité des images affichées ou les besoins en calcul de l'application. Différentes solutions ont déjà été proposées dans la littérature mais aucune d'entre elles ne satisfait l'ensemble des besoins. L'objectif de cette thèse est de proposer une solution alternative, c'est à dire une nouvelle architecture client-serveur dans laquelle l'interconnexion des dispositifs mobiles est complètement exploitée. Les principales conditions de mise en œuvre seront traitées: - Minimiser le trafic réseau - Réduire les besoins en puissance de calcul du terminal, et - Préserver l'expérience utilisateur par rapport à une exécution locale. Tout d'abord, un cadre formel est développé afin de définir et modéliser des applications graphiques 3D distribuées. Ensuite, une nouvelle architecture, permettant de dépasser certains inconvénients que l'on trouve dans des architectures de l'état de l'art, est présentée. La conception de la nouvelle architecture client-serveur est validée par l'implémentation d'un jeu et la mise œuvre de simulations. / With the development of the computer networks, mainly the Internet, it became easier to develop applications where the execution is shared between a local computer, the Client, and one located on the other side of the network communication channel, the Server. The hardware advancements in the recent years made it possible to display 3D graphics (games, map navigation, virtual worlds) on mobile devices. However, executing these complex applications on the client terminal is not possible without reducing the quality of the displayed graphics or lowering its processing requirements. Different solutions have already been proposed in academic publications; however none of them satisfies all requirements. The objective of this thesis is to propose an alternative solution for a new client-server architecture where the connectedness of the mobile devices is fully exploited. Several main requirements are addressed: - Minimize the network traffic, - Reduce the required computational power on the terminal, and - Preserve the user experience compared with local execution. First a formal framework is designed that can effectively define and model distributed applications for 3D graphics. Then a model of new architecture is presented, that overcomes the disadvantages of the architectures presented in the state of the art. The core of the architecture is the MPEG-4 standard, which is used to transfer the data between the server and the client in a compressed manner. The last part of explores the design of architectures optimized for running on mobile devices. The design of the new client-server architecture is validated by implementing a game and running simulations.

For some new multimedia applications using Mpeg-4 or Mpeg-7 video coding standards, it is important to find the main objects in a video frame. In this thesis, we propose a neuro-fuzzy modeling approach to the detection of human face and body. Firstly, a fuzzy clustering technique is performed to segment a video frame into clusters to generating several fuzzy rules. Secondly, chrominance and motion features are used to roughly classify the clusters into foreground and background, respectively. Finally, the fuzzy rules are refined by a fuzzy neural network, and the ambiguous regions between foreground and background are further distinguished by the fuzzy neural network. Our method improves the correctness of human face and body detection by getting training data more precisely. Besides, we can extract the VOs correctly even the VOs have no obvious motion in the video sequence.

Traditional Mobile IP supports only one tunnel between HA (Home Agent) and FA (Foreign Agent) for MN (Mobile Node) to transmit data from CN (Corresponding Node) to MN during handoff. To alleviate traffic load, in this Thesis, we propose a multiple-tunnel approach by setting up a secondary tunnel in addition to the primary tunnel. HA can split the video stream from the primary tunnel to the secondary tunnel when the former encounters high traffic load. Thus, quality of video stream from CN to MN can be guaranteed through the proposed multiple-tunnel schemes. For the purpose of validation, we implement the multiple-tunnel schemes on Linux platform for HA, FA, and MN to support video stream splitting. Specifically, if HA detects that high system load occurs on FA, an MPEG-4 packet filter is activated on HA to split some portions of video packets from the primary tunnel to the secondary tunnel based on I/B/P frame types. Video receiver on MN can then successfully recover these two divided video packets and playback the complete stream smoothly. Three experiments for validation are developed. They are (i) a simple Mobile IP handoff, (ii) Different bit rates to activate the stream splitting mechanism, and (iii) automatic adjustment of stream splitting according to system load. The experimental results have proved that the proposed multiple-tunnel schemes can substantially improve the quality of video streams.

With the development of the computer networks, mainly the Internet, it became easier to develop applications where the execution is shared between a local computer, the Client, and one located on the other side of the network communication channel, the Server. The hardware advancements in the recent years made it possible to display 3D graphics (games, map navigation, virtual worlds) on mobile devices. However, executing these complex applications on the client terminal is not possible without reducing the quality of the displayed graphics or lowering its processing requirements. Different solutions have already been proposed in academic publications; however none of them satisfies all requirements. The objective of this thesis is to propose an alternative solution for a new client-server architecture where the connectedness of the mobile devices is fully exploited. Several main requirements are addressed: - Minimize the network traffic, - Reduce the required computational power on the terminal, and - Preserve the user experience compared with local execution. First a formal framework is designed that can effectively define and model distributed applications for 3D graphics. Then a model of new architecture is presented, that overcomes the disadvantages of the architectures presented in the state of the art. The core of the architecture is the MPEG-4 standard, which is used to transfer the data between the server and the client in a compressed manner. The last part of explores the design of architectures optimized for running on mobile devices. The design of the new client-server architecture is validated by implementing a game and running simulations.

No / Geometric modelling using Partial Differential Equations (PDEs) has been gradually recognised due to its smooth instinct, as well as the ability to generate a variety of geometric shapes by intuitively manipulating a relatively small set of PDE boundary curves. In this paper we explore and demonstrate the feasibility of the PDE method in facial geometry parameterisation. The geometry of a generic face is approximated by evaluating spectral solutions to a group of fourth order elliptic PDEs. Our PDE-based parameterisation scheme can produce and animate a high-resolution 3D face with a relatively small number of parameters. By taking advantage of parametric representation, the PDE method can use one fixed animation scheme to manipulate the facial geometry in varying Levels of Detail (LODs), without any further process.

O trabalho apresentado nesta tese trata do desenvolvimento de técnicas com suporte à ciência de contexto, baseadas nos padrões MPEG-4 e MPEG-7, para personalizar e adaptar conteúdo em TV Interativa. Um dos desafios dessa área é desenvolvimento de programas personalizados com rico conteúdo multimídia, com alta interatividade e que, além disso, sejam acessíveis a partir de uma variedade de dispositivos (fixos ou móveis), atendendo às expectativas de interação e de acesso dos usuários. Grande parte do problema está no fato de que os modos encontrados na literatura para representar, descrever e compor programas de TV Interativa não oferecem suporte a contexto, não permitem a separação entre descrições de programas e descrições de objetos e possuem baixa granulosidade de segmentação. Essas características dificultam e, em alguns casos, impedem o desenvolvimento de aplicações avançadas em TV Interativa. As técnicas desenvolvidas neste trabalho são baseadas em esquemas de descrição, compatíveis com o padrão MPEG-7, e na segmentação de programas em objetos MPEG-4. Os esquemas são utilizados para descrever a estrutura, a composição e a semântica de programas e de seus objetos componentes. Também foi definida e implantada uma infra-estrutura para produção, distribuição e consumo de programas. A utilização conjunta da infra-estrutura e das técnicas permite o desenvolvimento de aplicações avançadas em TV Interativa. Como um exemplo dessas aplicações, foi desenvolvido um serviço automático para personalizar e adaptar programas de TV Interativa, permitindo que um usuário possa acessar, sob demanda, programas especialmente produzidos para ele, contendo apenas assuntos de seu interesse e permitindo que o acesso possa ser realizado por dispositivos fixos ou móveis. / The work presented in this thesis developed techniques with context-awareness support, based on the MPEG-4 and MPEG-7 standards, in order to personalize and to adapt Interactive TV content. One of the challenges in this area is the development of personalized programs with rich multimedia content, high interactivity and accessibility through a variety of devices (mobile and non-mobile). Most part of the problem is that the approaches found in literature do not provide context support, do not allow separation between programs and objects descriptions and have low level of segmentation granularity. These features make difficult or impossible, in some cases, the development of Interactive TV applications. The techniques developed in this work are based on MPEG-7 compliant schemes and on programs segmentation into MPEG-4 objects. The schemes are used to describe structure, composition and semantics of programs and component objects. An infra-structure to creation, delivery and consumption of Interactive TV programs was also defined. The joint utilization of infra-structure and techniques allows for the development of Interactive TV advanced applications. As an example of these applications, this work developed an automatic Interactive TV personalization and adaptation service. This service allows a user to access, on-demand, a program specially designed to match his interests and allowing content access through devices with mobile and non-mobile features.

Made available in DSpace on 2016-06-02T19:05:17Z (GMT). No. of bitstreams: 1 DissMML.pdf: 1887422 bytes, checksum: 213fe8c28a477776b42e8c6ef861a171 (MD5) Previous issue date: 2003-08-21 / This work describes the implementation of a support structure to 3D virtual networked games, based on the emergent standard multiuser MPEG-4 in a Gnutella hybrid peer-to-peer network. This solution minimizes the disadvantages of the existent hybrid solutions, that they are based on proxies, which have to be re-configured whenever a new application appears in the net. For that, the code that implements the Gnutella network it was modified from way to include a service of search of games and of active sessions. Two defined components and specified by the emergent standard MPEG-4 MU were implemented and integrated into the Gnutella network for games session control and updating of the scenes. When a node designated as controller leaves, another should assume in a fast and continuous way. Those, among other challenges in the implementation of multiuser games as peer-to-peer applications, they will be discussed in this work, together with the integration of the technologies Gnutella and MPEG-4 MU. The evaluation of this implementation allowed to conclude the some topics about the adaptation of those networks in the support to applications that demand continuous collaboration, as it is the case of a 3D game in that multiples participant constantly alter the scene and also the viability of implementing a session controller in one of the nodes of the network. / Este trabalho descreve a implementação de uma estrutura de suporte a jogos virtuais 3D em rede, baseada no padrão emergente MPEG-4 multiusuário em uma rede Gnutella peer-to-peer híbrida. Esta solução minimiza as desvantagens das soluções híbridas existentes, que são baseadas em proxies, as quais têm que ser re-configuradas sempre que uma nova aplicação surge na rede. Para isso, o código que implementa a rede Gnutella foi modificado de modo a incluir um serviço de busca de jogos e de sessões ativas. Dois componentes definidos e especificados pelo padrão emergente MPEG-4 MU foram implementados e integrados à rede Gnutella para controle de sessão de jogos e atualização das cenas. Quando um nodo designado como controlador sai, outro deve assumir de forma rápida e contínua. Esses, entre outros desafios na implementação de jogos multiusuário como aplicações peer-to-peer, serão discutidos neste trabalho, juntamente com a integração das tecnologias Gnutella e MPEG-4 MU. A avaliação desta implementação nos permitiu chegar a algumas conclusões sobre a adequação dessas redes no suporte a aplicações que exigem colaboração contínua, como é o caso de um jogo 3D em que múltiplos participantes alteram a cena constantemente e também a viabilidade de se implementar um controlador de sessão em um dos nodos da rede.