Kassel, Universiẗat, Diss., 2007.

Com a padronização das redes óticas passivas, em particular do GPON (gigabit-capable passive optical network) adotada no Brasil, uma nova gama de serviços passou a ser viável, dentre eles a transmissão de canais de TV para assinantes usando o protocolo IP (Internet protocol), sistema conhecido como IPTV. Este processo apresenta inúmeras vantagens, dentre elas a possibilidade de um número maior de canais e com qualidade variável. O grande inconveniente neste sistema é que em qualquer sistema de transmissão de TV digital o tempo de troca de canais, conhecido como tempo de zapping, pode chegar a alguns segundos. Para reduzir este problema, este trabalho descreve um processo de codificação e transmissão de IPTV em redes GPON que reduz o tempo de zapping, podendo chegar ao tempo de recuperação de um quadro (frame). O estudo foi baseado na codificação escalável em qualidade (SNR, signal to noise ratio) proposta no padrão MPEG-2 (Moving Picture Experts Group) e pode ser facilmente portado para outros padrões de codificação como os FGSs (fine grain scalability) do MPEG-4. O transporte utiliza a característica multicast das redes GPON além do protocolo IGMP (Internet group management protocol). Uma vez que o sistema IPTV propicia ao assinante vantagens como, o aumento do número de canais e a melhoria da qualidade de cada um deles devido à flexibilização da banda, este trabalho pressupõe que o assinante aceitará uma qualidade de vídeo inferior, no momento do zapping, desde que aumente com o decorrer do tempo. O aumento da qualidade é ilustrado por curvas comparativas, que mostram os tempos entre a mudança do canal, a entrada dele em baixa resolução e a melhora progressiva até a estabilidade em qualidade máxima. / With the standardization of passive optical networks, in particular GPON (gigabit-capable passive optical networks), which is adopted in Brazil, a new range of services become feasible, among them TV channels transmission to subscribers using the IP (Internet protocol), known as IPTV system, is one of the most important. This process has many advantages, including the possibility of offering a greater number of channels with variable quality. The greater inconvenience of this solution is that in any system of digital TV transmission the time to exchange channels, known as zapping time, can reach some seconds. To reduce this problem, this M.Sc thesis proposes a coding and transmission process for IPTV in GPON networks that reduces the zapping time to values smaller than one frame time. This work is based on the scalable SNR (signal to noise ratio) proposed in MPEG-2 standard and can be easily ported to other standards like FGS (fine grain scalability) in MPEG-4. Transport uses GPON multicast characteristics beside IGMP (Internet group management protocol). Once IPTV system offers many advantages like, increasing number of channels and better image quality per channel since bandwidth can be flexible. It is assumed that the IPTV subscriber will accept low video quality, at the zapping moment, but quality will increase progressively. Comparative graphics show the quality increase in terms of time between zapping, low quality video starting and the progressive quality increase up to stability in full quality.

Com a padronização das redes óticas passivas, em particular do GPON (gigabit-capable passive optical network) adotada no Brasil, uma nova gama de serviços passou a ser viável, dentre eles a transmissão de canais de TV para assinantes usando o protocolo IP (Internet protocol), sistema conhecido como IPTV. Este processo apresenta inúmeras vantagens, dentre elas a possibilidade de um número maior de canais e com qualidade variável. O grande inconveniente neste sistema é que em qualquer sistema de transmissão de TV digital o tempo de troca de canais, conhecido como tempo de zapping, pode chegar a alguns segundos. Para reduzir este problema, este trabalho descreve um processo de codificação e transmissão de IPTV em redes GPON que reduz o tempo de zapping, podendo chegar ao tempo de recuperação de um quadro (frame). O estudo foi baseado na codificação escalável em qualidade (SNR, signal to noise ratio) proposta no padrão MPEG-2 (Moving Picture Experts Group) e pode ser facilmente portado para outros padrões de codificação como os FGSs (fine grain scalability) do MPEG-4. O transporte utiliza a característica multicast das redes GPON além do protocolo IGMP (Internet group management protocol). Uma vez que o sistema IPTV propicia ao assinante vantagens como, o aumento do número de canais e a melhoria da qualidade de cada um deles devido à flexibilização da banda, este trabalho pressupõe que o assinante aceitará uma qualidade de vídeo inferior, no momento do zapping, desde que aumente com o decorrer do tempo. O aumento da qualidade é ilustrado por curvas comparativas, que mostram os tempos entre a mudança do canal, a entrada dele em baixa resolução e a melhora progressiva até a estabilidade em qualidade máxima. / With the standardization of passive optical networks, in particular GPON (gigabit-capable passive optical networks), which is adopted in Brazil, a new range of services become feasible, among them TV channels transmission to subscribers using the IP (Internet protocol), known as IPTV system, is one of the most important. This process has many advantages, including the possibility of offering a greater number of channels with variable quality. The greater inconvenience of this solution is that in any system of digital TV transmission the time to exchange channels, known as zapping time, can reach some seconds. To reduce this problem, this M.Sc thesis proposes a coding and transmission process for IPTV in GPON networks that reduces the zapping time to values smaller than one frame time. This work is based on the scalable SNR (signal to noise ratio) proposed in MPEG-2 standard and can be easily ported to other standards like FGS (fine grain scalability) in MPEG-4. Transport uses GPON multicast characteristics beside IGMP (Internet group management protocol). Once IPTV system offers many advantages like, increasing number of channels and better image quality per channel since bandwidth can be flexible. It is assumed that the IPTV subscriber will accept low video quality, at the zapping moment, but quality will increase progressively. Comparative graphics show the quality increase in terms of time between zapping, low quality video starting and the progressive quality increase up to stability in full quality.

Cette thèse concerne l'investigation détaillée du problème du temps de zapping dans les réseaux d'opérateurs offrant un service IPTY basé sur la technologie multicast. Cette investigation a conduit à plusieurs contributions qui permettent de substantiellement améliorer le temps de zapping dans ce type de réseau. Notre première contribution concerne la partie purement réseau. Nous avons proposé d'optimiser le processus de changement de chaîne et ceci pour chaque version du protocole IGMP. Cette optimisation réduit la latence due au réseau sans pour autant augmenter la consommation de bande passante d'une manière significative. Nous avons modélisé le service IPTV Multicast pour estimer les pics de consommation de la bande passante pour permettre à l'opérateur de dimensionner son réseau. La deuxième contribution concerne la partie traitement du flux IPTV par le récepteur. Dans cette partie, nous avons proposé d'associer au flux principal un flux secondaire, version retardée du principal. La construction du flux secondaire se fait en donnant une priorité élevée aux paquets transportant des éléments d'une I-Frame par rapport à d'autres types d'éléments (P­ Frame, B-Frame, Voix et Data). Cette nouvelle règle de construction permet de réduire le délai d'attente de la première I­Frame nécessaire pour commencer la phase de décodage tout en réduisant le temps de remplissage du buffer. Dans un environnement réel, nous avons évalué cette contribution et constaté une réduction remarquable du temps de zapping. / This thesis involves a detailed investigation of the problem of IPTV zapping time in networks of operators providing IPTV service based on multicast technology. This investigation led to some contributions that can substantially improve the channel change time in this type of network.Our first contribution concerns the pure network. We proposed an optimization of the channels changing process for each version of the IGMP protocol. This optimization reduces network latency without significantly increasing the bandwidth consumption. We proposed also a model of multicast IPTV service that we used to estimate the maximum bandwidth demand. This model enables the operator to size the bandwidth availability in its network.The second contribution relates to the processing part of stream IPTV on the receiver. In this section, we proposed to combine the main flow to a secondary flow, delayed version of the main stream. The construction of the secondary stream is clone by giving high priority to packets carrying elements of an I-frame compared to other types of elements (P-Frame, B­-Frame, Voice and Data). This rule of construction can reduce the First I-Frame Delay required to start the decoding phase and at the same time reduce the Buffering Delay. In a real environment, we evaluated this contribution and measured a remarkable decline of the zapping time with our proposal.

Le zapping a institué, en même temps que de nouvelles conditions de réception, de nouvelles conditions de production et de circulation des messages. Cette étude veut mettre en relief l'évolution de différents genres de discours télévisuels - discours de divertissement, discours publicitaire, discours d'information - en rapport avec ces changements dans les modes de production en réaction au zapping. Il est question d'accélération, de fragmentation, de sensationnalisation et d'hybridation des genres, des changements de ton et de format qu'on a voulu observer dans les discours de trois genres télévisuels à deux époques de l'histoire de la télévision : au début des années 1970, avant cette intensification de l'usage de la télécommande entrainée par l'addition des nombreux choix de programmes, et aujourd'hui (2010), alors que le zapping est devenu un mode de réception et de production des discours télévisuels assez généralisé. Plusieurs publicités, deux téléromans, deux talk-shows et deux téléjournaux sont analysés. ______________________________________________________________________________ MOTS-CLÉS DE L’AUTEUR : Zapping, effets du zapping, télévision, téléspectateur, production télévisuelle, diffusion, réception, discours télévisuels, discours des médias, conversation, accélération, fragmentation, publicité, téléroman, talkshow, journal télévisé, information.

The so-called family-viewing hour, the eight to nine o’clock hour of prime time, is one of the most watched hours of television by both adults and children. Advertisers, of course, favor shows that draw large audiences so their product presentations or commercials are witnessed by masses of people. Now, because of videocassette recorders and other similar control devices, viewers are eliminating commercials from their viewing experience1 and advertisers are clamoring for new ways to get their products into the mind of the consumer.2 To counteract this commercial avoidance by consumers, advertisers are embedding products within television programming thereby hindering the viewer’s ability to eliminate commercials or product promotions. The result is that products that are normally not viewed become part of the viewing experience. This study revealed that the family-viewing hour is laden with product placements that include a variety of different types of products and brands.