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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
91

Robust error control and optimal bit allocation for image and video transmission over wireless channels /

Cai, Jianfei, January 2002 (has links)
Thesis (Ph. D.)--University of Missouri-Columbia, 2002. / Typescript. Vita. Includes bibliographical references (leaves 163-177). Also available on the Internet.
92

Robust error control and optimal bit allocation for image and video transmission over wireless channels

Cai, Jianfei, January 2002 (has links)
Thesis (Ph. D.)--University of Missouri-Columbia, 2002. / Typescript. Vita. Includes bibliographical references (leaves 163-177). Also available on the Internet.
93

Optical Encryption Techniques for Color Image and Hyperspectral Data / Techniques de chiffrement optique pour des images couleurs et des données hyperspectrales

Chen, Hang 11 December 2017 (has links)
La sécurité est un problème important dans la transmission et le stockage de l'image, tandis que le cryptage est un moyen d'assurer la sécurité qui est requise dans de nombreuses applications (télévision par câble, la communication d'images militaires, systèmes d'imagerie confidentielle, etc.). Toutefois, à l'instar du message texte, les données images présentent des caractéristiques spéciales telles que la haute capacité, la redondance et la haute corrélation entre les pixels, et nécessite souvent une transmission et des traitements temps réel pour certaines applications. Construire un système rapide et efficace de cryptographie d'images suscite un intérêt considérable. C'est dans ce contexte qu’ont été menés ces travaux thèse qui portent sur l’élaboration d’un corrélateur optique en termes de cryptage/décryptage des données pour son implémentation dans un montage optique innovant. L’objectif de ces travaux est de réaliser un système optique de chiffrement sur la base d'exploitation de transformation optique et de générateurs chaotiques. L'idée originale des travaux consiste à exploiter la non-linéarité des systèmes chaotiques comme clés de chiffrement pour les systèmes optiques de chiffrement d'images multispectrales. Dans ces travaux de thèse, nous avons proposés et évalués plusieurs chiffrements d'images à base d’un système hyperchaotique et de transformées optiques (gyrator, Fourier, Baker , Arnold et Gerchberg- Saxton) à partir d’un processus de cryptage reposant sur une décomposition composants RVB et un encodage dans un flux dimensionnel d’images couleurs. L'originalité des solutions de chiffrement adoptée reposent sur l'exploitation de signaux réellement aléatoires à travers la mise en œuvre de générateurs hyperchaotiques pour la génération de données aléatoires sous forme images comme base de matrices de clés de chiffrement. En effet, ces générateurs présentent des propriétés et des caractéristiques fondamentales en termes de cryptage car il présente une non-linéarité, une imprédictibilité et une extrême sensibilité aux conditions initiales les rendant très intéressantes pour le développement de clés de chiffrement par flot. L’algorithme mis en œuvre permet d'extraire en temps réel les caractéristiques de texture dans les différentes bandes spectrales d'images en vue d’évaluer et de détecter les teneurs potentielles en information et dont les transmissions doivent être sécurisée via une transmission optique / Optical information security is one of the most important research directions in information science and technology, especially in the field of copyright protection, confidential information transmission/storage and military remote sensing. Since double random phase encoding technology (DRPE) was proposed, optical image encryption technology has become the main topic of optical information security and it has been developed and studied deeply. Optical encryption techniques offer the possibility of high-speed parallel processing of two dimension image data and hiding information in many different dimensions. In this context, much significant research and investigation on optical image encryption have been presented based on DRPE or further optical operation, such as digital holography, Fresnel transform, gyrator transform. Simultaneously, the encrypted image has been extended from single gray image to double image, color image and multi-image. However, the hyperspectral image, as a significant element in military and commercial remote sensing, has not been deeply researched in optical encryption area until now. This work extends the optical encryption technology from color image to hyperspectral image. For better comprehension of hyperspectral image encryption, this work begins with the introduction and analysis of the characteristics of hyperspectral cube. Subsequently, several kinds of encryption schemes for color image, including symmetric and asymmetric cryptosystem, are presented individually. Furthermore, the optical encryption algorithms for hyperspectral cube are designed for securing both the spatial and spectral information simultaneously. Some numerical simulations are given to validate the performance of the proposed encryption schemes. The corresponding attack experiment results demonstrate the capability and robustness of the approaches designed in this work. The research in this dissertation provides reference for the further practicality of hyperspectral image encryption
94

Video transcoding using machine learning

Unknown Date (has links)
The field of Video Transcoding has been evolving throughout the past ten years. The need for transcoding of video files has greatly increased because of the new upcoming standards which are incompatible with old ones. This thesis takes the method of using machine learning for video transcoding mode decisions and discusses ways to improve the process of generating the algorithm for implementation in different video transcoders. The transcoding methods used decrease the complexity in the mode decision inside the video encoder. Also methods which automate and improve results are discussed and implemented in two different sets of transcoders: H.263 to VP6 , and MPEG-2 to H.264. Both of these transcoders have shown a complexity loss of almost 50%. Video transcoding is important because the quantity of video standards have been increasing while devices usually can only decode one specific codec. / by Christopher Holder. / Thesis (M.S.C.S.)--Florida Atlantic University, 2008. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2008. Mode of access: World Wide Web.
95

Analise de desempenho de transmissão de video em redes IEEE 802.11 visando a estruturação de canais de retorno para TV digital / Performance analysis of video transmission in IEEE 802.11 networks aimed at structuring the return channel digital TV

Ribeiro, Thatiane Cristina dos Santos de Carvalho, 1982- 12 August 2018 (has links)
Orientador: Yuzo Iano / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-12T15:19:02Z (GMT). No. of bitstreams: 1 Ribeiro_ThatianeCristinadosSantosdeCarvalho_M.pdf: 2904973 bytes, checksum: e3c67793847764cf8eac05c50f45b48f (MD5) Previous issue date: 2008 / Resumo: A transmissão de vídeo em redes Wireless é abordada pela pesquisa, devido o grande aumento na utilização dessas redes na ultima década. O acesso à banda larga por essas redes é feito de forma eficiente, rápida e com baixo custo de implementação e manutenção da rede. A motivação para o desenvolvimento é utilizar essas redes e a rede IPTV para promover a interatividade e uma forma do canal de retorno para Sistemas de Televisão Digital, que estão sendo implementadas atualmente no Brasil. O canal de Retorno da TV Digital é importante para o sistema, pois um dos objetivos é prover a interatividade entre os usuários. Isso deve ser feito de forma simples com baixo custo e com tecnologia compatível a região do usuário. A simulação trata de um sistema de transmissão unicast que seria semelhante a uma interatividade local e dedicada. O usuário transmite o conteúdo de uma só vez. Os dados que são transmitidos pela provedora de serviços, são armazenados no set-top-box, e só são modificados em caso de novo fluxo de dados, quando há atualização ou acesso a nova área de serviços. Os testes feitos durante a pesquisa, transmitem conteúdo em tempo real e avaliam de forma quantitativa o desempenho das redes IEEE 802.11b e IEEE 802.11g. / Abstract: The streaming video transmission on Wireless networks is concerned in the research due to the large increase in the use of such networks in the last decade. Broadband access for these networks is made efficiently, quickly and with low implementation and maintenance costs of the network. The motivation for developing this research is to use these networks and IPTV network to promote interactivity and a return channel for digital television system, currently being implemented in Brazil. The return channel is important for the Digital TV system, because one of the goals is to provide interactivity for the users. This should be done in a simple, low cost way and with technology compatible in the region of the user. The simulation deals with a unicast transmission system which is similar to a local and dedicated interactivity. The user transmits all the contents at once. The data transmitted by a service provider are stored on set-top box and are modified only in case of new data flow, when there are updates or access to new area of services. The tests performed during the research, it was broadcasted contents in real time and evaluated quantitative the performance of IEEE 802.11b and IEEE 802.11g networks. / Mestrado / Telecomunicações e Telemática / Mestre em Engenharia Elétrica
96

Video Compression Through Spatial Frequency Based Motion Estimation And Compensation

Menezes, Vinod 02 1900 (has links) (PDF)
No description available.
97

Optimisation de la transmission d'images dans les réseaux de capteurs pour des applications critiques de surveillance / Optimization of image transmission in wireless sensor networks for mission-critical surveillance applications

Diop, El hadji Serigne Mamour 17 June 2014 (has links)
L’émergence de petites caméras CMOS et de microphones MEMS, à coût et puissance réduits, a contribué au développement d’une technologie permettant la transmission de flux multimédia (audio, image, vidéo) : les réseaux de capteurs multimédia. Cette technologie, offrant de nouvelles perspectives d’applications potentielles où la collecte d’informations visuelles et/ou acoustiques apporte une plus- value certaine, suscite un intérêt manifeste. Avec des données multimédia, la qualité de service devient désormais une exigence fondamentale pour la transmission dans un environnement contraint en ressources. Dans le contexte spécifique de cette thèse, nous considérons un déploiement par voie aérienne d’une grande quantité de capteurs image pour des applications critiques de surveillance telles que la détection d’intrusion ou des opérations de recherche et sauvetage. La prise en compte de la criticité des applications constitue un aspect important de cette thèse, novateur par rapport aux contributions déjà effectuées dans le domaine. Nos travaux se fondent sur une méthode d’ordonnancement adaptatif de l’activité des capteurs image qui fournit, pour chacun d’entre eux, son ensemble de cover-sets. La détection d’un événement dans le réseau déclenche la transmission d’une large quantité d’informations visuelles, émanant de plusieurs sources pour résoudre les ambiguïtés. L’objectif de cette thèse est d’optimiser cette transmission simultanée d’images causant des désagréments sur le réseau. Nous avons tout d’abord proposé une stratégie de sélection des cover-sets pertinents à activer pour une transmission efficace des images capturées. Cette stratégie, basée sur des critères d’état et de voisinage, assure un compromis entre autonomie et criticité. Une extension multi-chemin de GPSR assure la remontée des images émises des sources sélectionnées au puits. Une seconde contribution, également une approche de sélection, se fonde sur les informations de chemins à 2 sauts pour la sélection des cover-sets. Contrairement à la précédente, elle accorde une priorité à la criticité par rapport à la préservation de l’énergie, même si cette préservation est faite de manière indirecte. Un protocole de routage multi-chemin T-GPSR essentiellement basé sur les informations à 2 sauts est associé à la seconde approche de sélection. Une étude de performances de la mobilité du puits sur les propositions basées sur les informations à 2 sauts constitue notre troisième contribution. / Recent advances of inexpensive and low-power CMOS cameras and MEMS mi- crophones have led to the emergence of Wireless Multimedia Sensor Networks (WMSNs). WMSNs promise a wide spectrum of potential applications which require to ubiquitously capture multimedia content (visual and audio information). To support the transmission of multimedia content in a resource constrained environment, WMSNs may require a certain level of quality of service (QoS) in terms of delay, bandwidth, jitter, reliability, quality level etc. In this thesis, we consider Wireless Image Sensor Networks (WISNs) where sensor nodes equipped with miniaturized visual cameras to provide accurate information in various geographical parts of an area of interest can be thrown in mass for mission-critical applications such as intrusion detection or search & rescue. An innovative and important aspect of this thesis is to take into account the criticality of applications. The network adopts an adaptive scheduling of image sensor node’s activity based on the application criticality level, where each node computes its cover-sets. So, event detection triggers the simulataneous transmission of a large volume of visual data from multiples sources to the Sink. The main objective of this thesis is to optimize this simultaneous transmission of images that can degrade network performance. With this goal in mind, we first proposed a multi-criteria approach to select the suitable cover-sets to be activated for reliable transmission of images in mission-critical applications. The proposed approach takes into account various parameters that affect the image quality at the Sink in a multi-hop transmission network and guarantees a compromise between autonomy and criticality. A modified version of GPSR routing protocol supporting the transmission of multimedia streams ensures the transfer of images from selected sources to the Sink. The second contribution consists in an optimized selection strategy based on 2-hop neighborhood information to determine the most relevant cover-sets to be activated to increase reliability for image transmission. This selection approach prioritizes the application’s criticality. A multipath extension of GPSR, called T-GPSR, wherein routing decisions are based 2-hop neighborhood information is also proposed. A performance study of the sink mobility on proposals based on 2-hop information is our third contribution.
98

A Java image editor and enhancer

Darbhamulla, Lalitha 01 January 2004 (has links)
The purpose of this project is to develop a Java Applet that provides all the tools needed for creating image fantasies. It lets the user pick a template and an image, and combine them together. The user can then apply image processing techniques such as rotation, zooming, blurring etc according to his/her requirements.
99

Quality strategy and method for transmission : application to image / Évaluation de la qualité des images dans un contexte de transmission

Xie, Xinwen 10 January 2019 (has links)
Cette thèse porte sur l’étude des stratégies d’amélioration de la qualité d’image dans les systèmes de communication sans fil et sur la conception de nouvelles métriques d’évaluation de la qualité. Tout d'abord, une nouvelle métrique de qualité d'image à référence réduite, basée sur un modèle statistique dans le domaine des ondelettes complexes, a été proposée. Les informations d’amplitude et de phase relatives des coefficients issues de la transformée en ondelettes complexes sont modélisées à l'aide de fonctions de densité de probabilité. Les paramètres associés à ces fonctions constituent la référence réduite qui sera transmise au récepteur. Ensuite, une approche basée sur les réseaux de neurones à régression généralisée est exploitée pour construire la relation de cartographie entre les caractéristiques de la référence réduite et le score objectif.Deuxièmement, avec la nouvelle métrique, une nouvelle stratégie de décodage est proposée pour la transmission d’image sur un canal de transmission sans fil réaliste. Ainsi, la qualité d’expérience (QoE) est améliorée tout en garantissant une bonne qualité de service (QoS). Pour cela, une nouvelle base d’images a été construite et des tests d’évaluation subjective de la qualité de ces images ont été effectués pour collecter les préférences visuelles des personnes lorsqu’elles sélectionnent les images avec différentes configurations de décodage. Un classificateur basé sur les algorithmes SVM et des k plus proches voisins sont utilisés pour la sélection automatique de la meilleure configuration de décodage.Enfin, une amélioration de la métrique a été proposée permettant de mieux prendre en compte les spécificités de la distorsion et la préférence des utilisateurs. Pour cela, nous avons combiné les caractéristiques globales et locales de l’image conduisant ainsi à une amélioration de la stratégie de décodage.Les résultats expérimentaux valident l'efficacité des métriques de qualité d'image et des stratégies de transmission d’images proposées. / This thesis focuses on the study of image quality strategies in wireless communication systems and the design of new quality evaluation metrics:Firstly, a new reduced-reference image quality metric, based on statistical model in complex wavelet domain, has been proposed. The magnitude and the relative phase information of the Dual-tree Complex Wavelet Transform coefficients are modelled by using probability density function and the parameters served as reduced-reference features which will be transmitted to the receiver. Then, a Generalized Regression Neural Network approach is exploited to construct the mapping relation between reduced-reference feature and the objective score.Secondly, with the new metric, a new decoding strategy is proposed for a realistic wireless transmission system, which can improve the quality of experience (QoE) while ensuring the quality of service (QoS). For this, a new database including large physiological vision tests has been constructed to collect the visual preference of people when they are selecting the images with different decoding configurations, and a classifier based on support vector machine or K-nearest neighboring is utilized to automatically select the decoding configuration.Finally, according to specific property of the distortion and people's preference, an improved metric has been proposed. It is the combination of global feature and local feature and has been demonstrated having a good performance in optimization of the decoding strategy.The experimental results validate the effectiveness of the proposed image quality metrics and the quality strategies.
100

Video anatomy : spatial-temporal video profile

Cai, Hongyuan 31 July 2014 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / A massive amount of videos are uploaded on video websites, smooth video browsing, editing, retrieval, and summarization are demanded. Most of the videos employ several types of camera operations for expanding field of view, emphasizing events, and expressing cinematic effect. To digest heterogeneous videos in video websites and databases, video clips are profiled to 2D image scroll containing both spatial and temporal information for video preview. The video profile is visually continuous, compact, scalable, and indexing to each frame. This work analyzes the camera kinematics including zoom, translation, and rotation, and categorize camera actions as their combinations. An automatic video summarization framework is proposed and developed. After conventional video clip segmentation and video segmentation for smooth camera operations, the global flow field under all camera actions has been investigated for profiling various types of video. A new algorithm has been designed to extract the major flow direction and convergence factor using condensed images. Then this work proposes a uniform scheme to segment video clips and sections, sample video volume across the major flow, compute flow convergence factor, in order to obtain an intrinsic scene space less influenced by the camera ego-motion. The motion blur technique has also been used to render dynamic targets in the profile. The resulting profile of video can be displayed in a video track to guide the access to video frames, help video editing, and facilitate the applications such as surveillance, visual archiving of environment, video retrieval, and online video preview.

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