Movies, songs, conferences, video streams and other multimedia services are spreading in everybody’s life, needs and work. Different types of audio and video codecs of various qualities appear to be used for different purposes. However, each codec can be suitable for a special usage, as for example a codec that can be use for high quality film may not be suitable for streaming it into network. The main purpose of this thesis is to compare the performance of different codecs in one particular scenario and indicate which codec performance is the best. The thesis work includes the investigation of several codec aspects (audio and video) and problems related to choosing a multimedia codec (coder/decoder) suitable for large-scale multimedia distribution over the Internet. More specifically, the work focuses on various features of modern media codecs, compares them and finds the best application for each of them. Furthermore, the thesis provides an overview of available research results related to this work and codec comparison tables for codecs and their features. Additionally, as part of this work, a testbed was developed to measure the performance of codecs when used to stream media over a network. The testbed enabled the collection of various QoS parameters, such as bandwidth usage and burst, size for each codec considered in this thesis. / Address: Minervavägen 22A, Room 2, 371 41 Karlskrona, sweden. Cel: +46706456674

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Made available in DSpace on 2014-06-12T16:01:05Z (GMT). No. of bitstreams: 2 arquivo7156_1.pdf: 2405287 bytes, checksum: 63f88801321ea61b8de43e420495d1b8 (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2005 / A tecnologia de Voz sobre IP (VoIP) nasceu da necessidade da convergência das redes de telefonia e dados, aproveitando uma infra-estrutura de alcance mundial, a Internet. Esta tecnologia traz como vantagem a redução dos custos telefônicos, além da possibilidade de agregar novos serviços à telefonia. A tecnologia de Voz sobre IP é o resultado da pesquisa em busca de novas soluções tecnológicas, numa área que movimenta milhões em dólares, a área de telecomunicações, podendo se tornar um fenômeno na Internet, assim como os aplicativos de e-mails e mensagens instantâneas. Muitas iniciativas de projetos de VoIP têm surgido nos últimos anos. Dentre essas iniciativas temos o Skype, um aplicativo VoIp de grande sucesso. O Skype é um aplicativo de VoIP que usa a tecnologia peer-to-peer (P2P) híbrida, chamando atenção pela qualidade de transmissão da voz. O Skype é uma empresa de telefonia virtual, oferecendo chamadas telefônicas gratuitas entre computadores no mundo inteiro. Possui, ainda, as soluções SkypeIn e SkypeOut para o acesso a Rede Pública de Telefonia. Outra iniciativa de aplicativos na tecnologia VoIP é o XVoice. O XVoice foi um dos resultados do Grupo de Trabalho GT-P2P da Rede Nacional de Pesquisa (RNP), sendo projetado para avaliar o tráfego de voz na rede da RNP. O levantamento de requisitos para desenvolver o XVoice demandou um estudo aprofundado sobre o Skype e os protocolos e codecs que são utilizados em aplicações de Voz sobre IP. O XVoice é um aplicativo VoIP que usa a tecnologia peer-to-peer pura. Peer-to-peer é um modelo de comunicação no qual cada nó tem as mesmas capacidades e responsabilidades, e ambos podem iniciar uma sessão de comunicação, contrastando com o modelo cliente/servidor. O objetivo deste trabalho é avaliar os aplicativos de VoIP Skype e XVoice, descrevendo a metodologia e ferramentas utilizadas nesta avaliação. Na avaliação realizada neste trabalho, observou-se que os aplicativos Skype e XVoice possuem desempenhos similares, conforme mostrado nos resultados obtidos

Submitted by Programa de P?s-Gradua??o Engenharia El?trica (ppgee@ifpb.edu.br) on 2018-04-17T17:04:37Z No. of bitstreams: 1 46- Anselmo de Vasconcelos Cavalcante - AN?LISE DOS EFEITOS DE CODECS DE ?UDIO NA AVALIA??O DE DESVIOS VOCAIS.pdf: 2426098 bytes, checksum: 4e9dc4ae38d3b0d367a6d38e535f9a00 (MD5) / Approved for entry into archive by Programa de P?s-Gradua??o Engenharia El?trica (ppgee@ifpb.edu.br) on 2018-04-17T17:05:40Z (GMT) No. of bitstreams: 1 46- Anselmo de Vasconcelos Cavalcante - AN?LISE DOS EFEITOS DE CODECS DE ?UDIO NA AVALIA??O DE DESVIOS VOCAIS.pdf: 2426098 bytes, checksum: 4e9dc4ae38d3b0d367a6d38e535f9a00 (MD5) / Made available in DSpace on 2018-04-17T17:05:40Z (GMT). No. of bitstreams: 1 46- Anselmo de Vasconcelos Cavalcante - AN?LISE DOS EFEITOS DE CODECS DE ?UDIO NA AVALIA??O DE DESVIOS VOCAIS.pdf: 2426098 bytes, checksum: 4e9dc4ae38d3b0d367a6d38e535f9a00 (MD5) Previous issue date: 2018-03-19 / Este trabalho apresenta um estudo sobre as implica??es no uso de diferentes codecs de ?udio na an?lise perceptiva e ac?stica da voz. Um cen?rio de transmiss?o baseado em VoIP foi criado, empregando o Asterisk e o softphone Microsip, para auxiliar no diagn?stico de desvios vocais ? dist?ncia. Para este prop?sito, foram utilizados 36 sinais de vozes sintetizadas e 36 sinais de vozes reais, classificados como normais, com o desvio rugosidade e com o desvio soprosidade. Cada sinal foi submetido a seis transmiss?es, cada uma delas utilizando um codec espec?fico (G.711 Lei A, Speex32, GSM Full Rate, LPCM16, Opus24 e SILK16). Antes e ap?s cada transmiss?o, um especialista em voz realizou a classifica??o dos sinais quanto ao tipo de desvio e, com aux?lio do software VoxMetria, extraiu-se as medidas ac?sticas frequ?ncia fundamental, jitter, shimmer, GNE e desvio padr?o da frequ?ncia fundamental. Observou-se que, dentre os codecs analisados, o Opus24 foi aquele se mostrou o mais promissor para avalia??o da qualidade vocal, por ter sido o ?nico a apresentar taxa de acur?cia acima de 70%, tanto para os sinais sintetizados quanto para os sinais reais analisados. Este codec conseguiu manter os desvios vocais inalterados para avalia??o em mais de 85% dos sinais reais.

Les tests d'écoute subjectifs permettent d'évaluer la fiabilité de reproduction des systèmes de codage audio (codecs). Le projet présenté ici vise à évaluer la possibilité d'utiliser les réactions physiologiques (activité électrodermale, cardiaque, musculaire et cérébrale) à la place d'une note donnée par l'auditeur, afin de caractériser la performance d'un codec. Ceci permettrait d'avoir une méthode d'évaluation plus proche de la perception réelle de qualité audio du sujet. Des tests d'écoute mettant en oeuvre des dégradations audio bien connues en concours avec la mesure des réactions physiologiques ont été réalisés pour 4 auditeurs. L'analyse des résultats montre que certaines caractéristiques physiologiques permettent d'avoir une information fiable sur la qualité audio perçue, et ce de manière répétable pour près de 70% des signaux audio testés chez un sujet, et près de 60% des séquences audio testées chez tous les sujets. Ceci permet de postuler sur la faisabilité d'une telle méthode d'évaluation subjective des codecs audio.

This thesis deals with the possibilities of video conferencing in Asterisk PBX and their use in practice. They also described the contingencies and how its configuration. Particular attention is paid to the protocols SIP, IAX and H.323, which are described in one of the chapters. The thesis was created by the Asterisk PBX, which demonstrates cooperation with videoconferencing clients. The thesis describes the configuration files so that the central set. Conclusion the work assesses the use of codecs for different clients.

SADÍLEK, J. Libraries, information centers and their services in the context of ethical problems of the 21st century. Prague: Charles University, Faculty of Philosophy, 2017. 136 pp. Diploma thesis. The diploma thesis deals with questions of predominantly information ethics and encounter in practice. The aim of the thesis is to describe and analyze the ethical problems associated with information institutions, as well as to conduct research in Czech libraries. The work is divided into five parts. The first part deals with the theory of several types of ethics, describes the information society and also presents a topic of creative common theme as a topic of citation ethics. The second part deals with the codes of ethics of some information institutions, then devoted to libraries as a main interest of the work, described their definition and system in the Czech Republic. Subsequently is presented topic of ethic and libraries. The third part summarizes the topic of ethical codes and ethics on the websites of supranational, largely library organizations, along with some national ethical codes. The fourth part presents two examples of studies, one focusing on the Code of Ethic and the other on ethics violations in one of the libraries in Florida. The last, fifth part presents library research in the...

Technology advancement increases the usage of the internet day by day. One of the most used internet services is video streaming. The major advantage of video streaming is that it allows long distance communication between people without any delay. It is known that streaming video is one of the fastest growing industries, and it has been very beneficial to the world. As the use of video streaming is increasing rapidly, it is essential to have security for video streaming. A lot of methods to secure video streaming came into existence like authentication, protocol, or some secure web hosting sites. Every method is to secure the transmission of video streaming, so these methods use either key or any other additional things to secure it. Our approach is to have a secure video streaming method without using any additional key or software. So, the method here is to encrypt the video directly and then encode it to be in the streaming format. The encryption of the video is done by a method called obscuring method. And the performance evaluation is done to the method so as to check the stability and feasibility of the system.

Internet access has evolved in the last decade with the availability of smart handheld devices and high bandwidth offered by mobile networks at reduced costs. Multimedia traffic primarily video became the main share of global Internet traffic due to the popularity of multimedia supported social applications, online gaming, and IPTV. Thus, the success of any network based business model is dependent on service quality and Quality of Experience (QoE) is widely accepted as a means to describe user satisfaction with a service. QoE can be influenced by numerous factors ranging from content liking to system and context-related artifacts. In this thesis, a holistic approach is adopted to evaluate the QoE of an end-user regarding video quality based on system, contextual and human factors. At the system level, an impact of the Maximum Transmission Unit (MTU), and the comparison of widely used video codecs in error-prone networks is investigated by using diverse streaming protocols on an emulated network. It is found that the myth of using small MTU for better performance in high-loss scenarios comes at a cost of increased latency at the intermediate nodes and doesn’t provide any gain in video quality. The performance of the Google royalty-free VP8 codec was also shown to be on par with the widely adopted and proprietary H.264, especially in scenarios involving high jitter. At a human level, user delight towards the shown stimulus, his or her mood along with the frequency of watching online content (contextual), and their impact on quality ratings are investigated. It is found that human-related personality traits tend to influence subjective ratings and highlight the requirement of more cohesive QoE models to estimate user perception.

Real time applications over IP network became widely used in different fields; social video conference, online educational lectures, industrial, military, and online robotic medical surgery. Online medical surgery over IP network has experienced rapid growth in the last few years primarily due to advances in technology (e.g., increased bandwidth; new cameras, monitors, and coder/decoders (CODECs)) and changes in the medical care environment (e.g., increased outpatient care, remote surgeries). The purpose of this study was to examine and analyze the impact of IP networks parameters; delay, jitter, throughput, and drop packet on the performance of real-time medical surgery videos sent across different IP networks; native IPv6, native IPv4, 6to4 and 6in4 tunneling transition mechanisms and compare the behavior of video packets over IP networks. The impact of each parameter over IP networks is examined by using different video codecs MPEG-1, MPEG-2, and MPEG-4. This study has been carried out with two main parts; theoretical and practical part, the theoretical part of this study focused on the calculations of various delays in IP networks such as transmission, processing, propagation, and queuing delays for video packet, while the practical part includes; examining of video codecs throughput over IP networks by using jperf tool and examining delay, jitter, and packet drops for different packet sizes by using IDT-G tool and how these parameters can affect quality of received video. The obtained theoretical and practical results were presented in different tables and plotted into different graphs to show the performance of real time video over IP networks. These results confirmed that video codecs MPEG-1, MPEG-2, and MPEG-4 were highly impacted by encapsulation and de-capsulation process except MPEG-4 codec, MPEG-4 was the least impacted by IPv4, IPv6, and IP transition mechanisms concerning throughput and wastage bandwidth. It also indicated that using IPv6-to-4 and IPv6-in-4 tunneling mechanisms caused more bandwidth wastage, high delay, jitter, and packet drop than IPv4 and IPv6.