Télévision

La télévision est un ensemble de techniques destinées à émettre et recevoir des séquences audiovisuelles, appelées programme télévisé : émissions, films et éventuellement de séquences publicitaires. Le contenu de ces programmes peut être exploité selon des procédés analogiques ou numériques, tandis que leur retransmission peut être opérée par ondes radioélectriques de type terrestre ou satellite, par réseau câblé de type coaxial, par réseau filaire de télécommunications xDSL ou Internet ou encore, par réseau à fibre optique. En langue française, l'appareil permettant d'afficher les images et restituer le son d'un programme est nommé « téléviseur » ou, par métonymie, « poste de télévision », « récepteur de télévision », simplement « télévision » ou encore par apocope « télé » ou siglaison : « TV ». La télévision est généralement conforme à un modèle économique, politique et culturel (financement public ou commercial, langues nationales ou régionales, genres et formats, réglementatio

Temporal and Inter-view Consistent Error Concealment Technique for Multiview plus Depth Video Broadcasting

Pascal Frossard, Thomas Maugey

Multiview plus depth (MVD) is an emerging video format with many applications, including 3-D television and free viewpoint television. During the broadcast of a compressed MVD video, transmission errors may cause the loss of whole frames, resulting in significant degradation of video quality. Error concealment techniques have been widely used to deal with transmission errors in video communication. However, the existing solutions do not address the requirement that the reconstructed frames should be consistent with neighboring frames, i.e., corresponding pixels should have consistent color information. We propose a new consistency model for error concealment of MVD video that allows one to maintain a high level of consistency between frames of the same view (temporal consistency) and those of neighboring views (inter-view consistency). We then propose an algorithm that uses our model to implement concealment in a consistent way. Simulations with the reference software for the multiview video coding project of the joint video team of the ISO/IEC MPEG and ITU-T VCEG show that our method outperforms benchmark techniques, including a baseline approach based on the boundary matching algorithm, with respect to both reconstruction quality and view consistency.

Institute of Electrical and Electronics Engineers2016

Modeling of Long-Term Multipactor Evolution in Microwave Components Including Dielectric Layers

Apostolos Sounas

Multipactor is a resonant vacuum discharge occurring in microwave components of satellite systems as well as in particle accelerators. Due to its undesirable effects, multipactor analysis constitutes a mandatory step in the design of modern satellite components and in performance studies of particle accelerators. To this end, the development of computational techniques for multipactor prediction attracts intense interest in the scientific community. The phenomenon evolves in two distinct phases: first, a fast growth of the electron population and, second, a steady state during which the population reaches a saturation level and remains almost constant. State-of-the-art computational models focus on the precise prediction of the initial multipactor phase, which defines whether the discharge occurs or not. However, a clear overview of the phenomenon also requires the analysis of the longterm multipactor evolution. Due to the high complexity introduced by considering saturation mechanisms, long-term multipactor evolution remains still unclear for many configurations of highly practical importance. Such a case is the multipactor analysis in the presence of dielectrics, a case dealt within this thesis. Motivated by the challenging nature of analyzing the multipactor steady state, this work aims to provide its own contribution to the modeling and the analysis of long-term multipactor evolution. For this, a sophisticated computational tool has been developed for the full-3D multipactor analysis, taking into account saturation mechanisms. In order to get a fast overview of the phenomenon, a generalized single-electron model has been developed which allows a multipactor analysis in any configuration with unidirectionallike electric field. Based on this 1D model, qualitative studies considering the effect of lowenergy electron collisions and of single-sided multipactor in non-uniform coaxial fields have been performed. As a further step, a multiple-particle, full-3D model able to consider the stochastic nature of the secondary emission phenomenon has been developed. The singleelectron model nicely supplements the robust 3D analysis by providing fast estimations for the most likely cases in which multipactor occurs. Saturation mechanisms have been considered, too, for both 1D and 3D approximations. Taking into account the induced charges on the metallic boundaries, a fast analysis of longterm multipactor is provided by the 1D model for the parallel plate and coaxial line cases. The saturation study is boosted in the 3D analysis by taking into account the mutual Coulomb interaction between particles. The developed multipactor model has been properly adapted in order to study long-term multipactor in the case of dielectric-loaded waveguides. Space charge effects as well as the effect of the surface charge developed on the dielectric layer have been both considered in the analysis. Particularly, in order to efficiently take into account the effect of the induced charges, a novel image method for the evaluation of the 3D Green function in multi-layered media has been developed. For the first time, a saturation steady state is identified in parallel plates loaded with a dielectric layer.

EPFL2015

Modeling of Long-Term Multipactor Evolution in Microwave Components Including Dielectric Layers

Apostolos Sounas

EPFL2015

Re-inventing television

Temporal and Inter-view Consistent Error Concealment Technique for Multiview plus Depth Video Broadcasting

Modeling of Long-Term Multipactor Evolution in Microwave Components Including Dielectric Layers

Re-inventing television

Temporal and Inter-view Consistent Error Concealment Technique for Multiview plus Depth Video Broadcasting

Modeling of Long-Term Multipactor Evolution in Microwave Components Including Dielectric Layers