As aplicações de live streaming em redes P2P têm grande potencial de crescimento, em popularidade e qualidade, mas são potencialmente vulneráveis ao ataque de poluição de conteúdo. Tal ataque corresponde a qualquer adulteração de áudio e/ou vídeo na mídia transmitida buscando ludibriar espectadores. A autenticação de blocos do fluxo de dados contínuo (stream) permite a detecção de conteúdo poluído e a possível identificação de pares maliciosos na rede P2P. A literatura contém diversas propostas de autenticação baseadas em assinatura digital leve e em amortização de assinatura digital. O presente trabalho, como nenhum anterior, compara tanto os esquemas de assinatura leve quanto os de amortização sob diferentes perspectivas de qualidade de transmissão (vídeos convencionais e de alta definição) em redes P2P de live streaming através da formularização analítica dos mesmos. Para isto, é feita uma comparação quantitativa de sobrecargas e nível de segurança, observando fenômenos e identificando desafios de pesquisa que precisarão ser vencidos. Particularmente, para avaliar a viabilidade dos esquemas, foi definido um coeficiente que leva em consideração o tempo total de transmissão e o custo computacional proporcionado pelo esquema estudado. Como uma das conclusões inéditas dessa análise, o esquema PARM2 obteve o melhor desempenho dentre os esquemas leves de assinatura. Já em relação aos esquemas de amortização, o Linear Digests se sobressaiu entre os demais. Por fim, foi analisada uma solução baseada na amortização de um esquema de assinatura leve, algo também inédito. A partir dessa análise em particular, foi possível observar que a autenticação é viável apenas com baixos e médios níveis de segurança em transmissões convencionais. Além disso, a partir dos resultados foi possível observar que o esquema de amortização Linear Digests deve ser utilizado isoladamente apenas em transmissões convencionais. Por fim, o esquema PARM2, se utilizado individualmente, não apresenta valores de coeficiente aceitáveis para os cenários estudados. / P2P live streaming applications have great potential for improvements in terms of popularity as well as quality. However, they are subject to pollution attacks, in which a malicious user tampers with audio/video of streams in order to trick other users. The authentication of blocks in a stream allows the detection of pollution in received content and can lead to the identification of malicious users. The literature includes several proposals of light digital signature schemes and amortization schemes. Our work, unlike previous ones, compares both amortization schemes and light signature schemes under di erent perspectives of transmission quality (convencional and high definition videos) in P2P live streaming by formulating equations for them. For such, it quantitatively compares overheads and security levels during P2P streaming sessions, identifying research challenges to be faced. In particular, to assess the viability of such schemes, we defined a coe cient that takes into account the total transmission time and computational cost provided by such scheme. As one of the novel findings of our analysis, the scheme PARM2 showed the best performance among light signature schemes. With respect to amortization, Linear Digests was the most e cient. Finally, we analyzed a solution based on the amortization of a light signature. From this particular analysis, we observed that the authentication is only feasible in conventional transmissions with low and medium security leves. In addition, the amortization scheme Linear Digests must be used in isolation only in conventional transmissions. Finally, the scheme PARM2, if used alone, has no acceptable coe cient values for the studied scenarios.

As aplicações de live streaming em redes P2P têm grande potencial de crescimento, em popularidade e qualidade, mas são potencialmente vulneráveis ao ataque de poluição de conteúdo. Tal ataque corresponde a qualquer adulteração de áudio e/ou vídeo na mídia transmitida buscando ludibriar espectadores. A autenticação de blocos do fluxo de dados contínuo (stream) permite a detecção de conteúdo poluído e a possível identificação de pares maliciosos na rede P2P. A literatura contém diversas propostas de autenticação baseadas em assinatura digital leve e em amortização de assinatura digital. O presente trabalho, como nenhum anterior, compara tanto os esquemas de assinatura leve quanto os de amortização sob diferentes perspectivas de qualidade de transmissão (vídeos convencionais e de alta definição) em redes P2P de live streaming através da formularização analítica dos mesmos. Para isto, é feita uma comparação quantitativa de sobrecargas e nível de segurança, observando fenômenos e identificando desafios de pesquisa que precisarão ser vencidos. Particularmente, para avaliar a viabilidade dos esquemas, foi definido um coeficiente que leva em consideração o tempo total de transmissão e o custo computacional proporcionado pelo esquema estudado. Como uma das conclusões inéditas dessa análise, o esquema PARM2 obteve o melhor desempenho dentre os esquemas leves de assinatura. Já em relação aos esquemas de amortização, o Linear Digests se sobressaiu entre os demais. Por fim, foi analisada uma solução baseada na amortização de um esquema de assinatura leve, algo também inédito. A partir dessa análise em particular, foi possível observar que a autenticação é viável apenas com baixos e médios níveis de segurança em transmissões convencionais. Além disso, a partir dos resultados foi possível observar que o esquema de amortização Linear Digests deve ser utilizado isoladamente apenas em transmissões convencionais. Por fim, o esquema PARM2, se utilizado individualmente, não apresenta valores de coeficiente aceitáveis para os cenários estudados. / P2P live streaming applications have great potential for improvements in terms of popularity as well as quality. However, they are subject to pollution attacks, in which a malicious user tampers with audio/video of streams in order to trick other users. The authentication of blocks in a stream allows the detection of pollution in received content and can lead to the identification of malicious users. The literature includes several proposals of light digital signature schemes and amortization schemes. Our work, unlike previous ones, compares both amortization schemes and light signature schemes under di erent perspectives of transmission quality (convencional and high definition videos) in P2P live streaming by formulating equations for them. For such, it quantitatively compares overheads and security levels during P2P streaming sessions, identifying research challenges to be faced. In particular, to assess the viability of such schemes, we defined a coe cient that takes into account the total transmission time and computational cost provided by such scheme. As one of the novel findings of our analysis, the scheme PARM2 showed the best performance among light signature schemes. With respect to amortization, Linear Digests was the most e cient. Finally, we analyzed a solution based on the amortization of a light signature. From this particular analysis, we observed that the authentication is only feasible in conventional transmissions with low and medium security leves. In addition, the amortization scheme Linear Digests must be used in isolation only in conventional transmissions. Finally, the scheme PARM2, if used alone, has no acceptable coe cient values for the studied scenarios.

There are multiple factors that influence auditory steaming. Some, like frequency separation or rate of presentation, have effects that are well understood while others remain contentious. Human behavioural studies and event-related potential (ERP) studies have shown dissociation between a pre-attentive sound segregation process and an attention-dependent process in forming perceptual objects and streams. This thesis first presents a model that synthetises the processes involved in auditory object creation. It includes sensory feature extraction based on research by Bregman (1990), sensory feature binding through an oscillatory neural network based on work by Wang (1995; 1996; 1999; 2005; 2008), work by Itti and Koch (2001a) for the saliency map, and finally, work by Wrigley and Brown (2004) for the architecture of single feature processing streams, the inhibition of return of the activation and the attentional leaky integrate and fire neuron. The model was tested using stimuli and an experimental paradigm used by Carlyon, Cusack, Foxton and Robertson (2001). Several modifications were then implemented to the initial model to bring it closer to psychological and cognitive validity. The second part of the thesis furthers the knowledge available concerning the influence of the time spent attending to a task on streaming. Two deviant detection experiments using triplet stimuli are presented. The first experiment is a follow-up of Thompson, Carlyon and Cusack (2011) and replicated their behavioural findings, showing that the time spent attending to a task enhances streaming, and that deviant detection is easier when one stream is perceived. The ERP results showed double decisions markers indicating that subjects may have made their deviant detection based on the absence of the time delayed deviant and confirmed their decision with its later presence. The second experiment investigated the effect of the time spent attending to the task in presence of a continuity illusion on streaming. It was found that the presence of this illusion prevented streaming in such a way that the pattern of the triplet was strengthened through time instead of separated into two streams, and that the deviant detection was easier the longer the subjects attended to the sound sequence.

Made available in DSpace on 2015-05-14T12:36:40Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 2054391 bytes, checksum: ef9f90118e5f1321521703ded66ff354 (MD5) Previous issue date: 2011-11-21 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The progress of science and technology coupled with the improvement of communication networks favoring the emergence of services to handle with growing volumes of data and the high transmission power available. Applications based on digital video are increasingly popular. They are widespread in multiples fields: telemedicine, artistic performances, techno-scientific events, entertainment, and advertising, among others. Proportionately, they are increasingly required higher levels of quality and delivery times getting shorter for the development of software systems. Therefore, this paper aims to map the state of the art in the development of applications based on digital video and show the necessity of having a framework that provides an abstraction for the development of systems in this area. Finally, is presented a case study of STYLO, a software framework that aims to encapsulate experiences in developing technologies that scope, providing ways for developers to reuse, usability and standardization of code and bringing greater productivity in their implementations. / O progresso da Ciência e Tecnologia aliado à melhoria das redes de comunicação, favorecem o surgimento de serviços para lidar com volumes crescentes de dados e com o alto poder de transmissão disponível. Aplicações baseadas em vídeo digital estão cada vez mais populares e atingem os mais diversos campos: Telemedicina, Arte e Tecnologia, entretenimento, publicidade, dentre outros. Proporcionalmente, são exigidos níveis cada vez mais altos de qualidade e prazos de entrega cada vez mais curtos para o desenvolvimento de sistemas de software. Diante disso, este trabalho faz um mapeamento do estado da arte no processo de desenvolvimento de aplicações baseadas em vídeo digital e mostra a necessidade de se ter um framework que forneça uma abstração para o desenvolvimento de sistemas nessa área. Além disso, é apresentado o STYLO, um arcabouço de software que tem como objetivo encapsular experiências adquiridas no desenvolvimento de tecnologias desse âmbito, provendo para os programadores formas de reuso, usabilidade e padronização de código e trazendo maior produtividade em suas implementações.

abstract: Stream processing has emerged as an important model of computation especially in the context of multimedia and communication sub-systems of embedded System-on-Chip (SoC) architectures. The dataflow nature of streaming applications allows them to be most naturally expressed as a set of kernels iteratively operating on continuous streams of data. The kernels are computationally intensive and are mainly characterized by real-time constraints that demand high throughput and data bandwidth with limited global data reuse. Conventional architectures fail to meet these demands due to their poorly matched execution models and the overheads associated with instruction and data movements. This work presents StreamWorks, a multi-core embedded architecture for energy-efficient stream computing. The basic processing element in the StreamWorks architecture is the StreamEngine (SE) which is responsible for iteratively executing a stream kernel. SE introduces an instruction locking mechanism that exploits the iterative nature of the kernels and enables fine-grain instruction reuse. Each instruction in a SE is locked to a Reservation Station (RS) and revitalizes itself after execution; thus never retiring from the RS. The entire kernel is hosted in RS Banks (RSBs) close to functional units for energy-efficient instruction delivery. The dataflow semantics of stream kernels are captured by a context-aware dataflow execution mode that efficiently exploits the Instruction Level Parallelism (ILP) and Data-level parallelism (DLP) within stream kernels. Multiple SEs are grouped together to form a StreamCluster (SC) that communicate via a local interconnect. A novel software FIFO virtualization technique with split-join functionality is proposed for efficient and scalable stream communication across SEs. The proposed communication mechanism exploits the Task-level parallelism (TLP) of the stream application. The performance and scalability of the communication mechanism is evaluated against the existing data movement schemes for scratchpad based multi-core architectures. Further, overlay schemes and architectural support are proposed that allow hosting any number of kernels on the StreamWorks architecture. The proposed oevrlay schemes for code management supports kernel(context) switching for the most common use cases and can be adapted for any multi-core architecture that use software managed local memories. The performance and energy-efficiency of the StreamWorks architecture is evaluated for stream kernel and application benchmarks by implementing the architecture in 45nm TSMC and comparison with a low power RISC core and a contemporary accelerator. / Dissertation/Thesis / Doctoral Dissertation Computer Science 2014

In many fields, there is a need for quick analysis of data. As the number of devices connected to the Internet grows, so does the amounts of data generated. The traditional way of analyzing large amounts of data has been by using batch processing, where the already collected data is pro-cessed. This process is time consuming, resulting in another trend emerg-ing: stream processing. Stream processing is when data is processed and stored as it arrives. Because of the velocity, volume and variations in data. Stream processing is best carried out in the main memory, and means processing and storing data as it arrives, which makes it a big challenge. This thesis focuses on developing a framework for the processing and storing of streaming temporal data enabling the data to be analyzed in real time. For this purpose, a server application was created consisting of approximate in-memory data synopsizes, called sketches, to process and store the input data. Furthermore, a client web application was created to query and analyze the data. The results show that the framework can sup-port simple aggregate queries with constant query time regardless to the volume of data. Also, it can process data 6.8 times faster than a traditional database system. All this implies that the system is scalable, at the same time it with a query error vs. memory trade-off. For a distribution of ~3000000 unique items it was concluded that the framework can provide very accurate answers, with an error rate less than 1.1%, for the trendiest data using about 100 times less space than the actual size of the data set.

The purpose of this thesis is to investigate and test the usage of HTTP/2 in dynamic adaptive video streaming as well as to take a look into how it can be used to benefit prefetching algorithms used with branched video. With a series of experiments the performance gains of using HTTP/2 rather than the older standard HTTP/1.1 has been investigated. The results has shown no significant change to player quality and buffer occupancy when using HTTP/2, though our tests has shown in a slight decrease in overall playback quality when using HTTP/2. When using a linear prefetch of two fragments an average quality improvement of 4.59% has been shown, however, the result is inconclusive due to variations in average quality between different values for how many fragments to prefetch. Average buffer occupancy has shown promise with a maximum increase of 12.58%, when using linear prefetch with three fragments. The values for buffer occupancy gains are conclusive. Two implementations for non-linear prefetching has been made. The first one uses HTTP/2 server push to deliver fragments for prefetching and the second one uses client-side invoked HTTP requests to pull fragments from the server. Using HTTP/2 server push has shown in a decrease of 2.5% in average total load time while using client-side pulling has shown in a decrease of 34% in average total load time.

Multi-video streaming allows the viewer to interact with the stream by choosing andswitching between several different camera angles to view the stream from. For this reportwe implement and evaluate adaptive multi-video streaming with dash.js. With the help ofdash.js and self-made additions, multiple parallel video streams which are synchronized intime are implemented to provide a good user experience with smooth switching betweenstreams. These streams will be delivered according to dash.js own HTTP-based AdaptiveStreaming algorithms to achieve adaptive streams for varying conditions. In order to optimizethe usage of the available bandwidth in terms of video quality in a multi-videoenvironment we implement probabilities of camera switching to adapt qualities and allocatedbandwidth of streams. By utilizing the functions of dash.js we create two prefetchingpolicies and analyze these results together with the standard non-prefetch dash.js implementationin a multi-view video environment. Our results present the improvements interms of stalling with a prefetch implementation and the possibility of a good policy tofurther optimize a multi-view video implementation in terms of stalling, quality and bandwidthusage. Evaluation of dash.js compatibility for a multi-view video environment is alsodiscussed where pros and cons of dash.js in their current state are presented.

The purpose of this thesis is to develop software to stream input and output audio from a large number of computers in a network to one specific computer in the same network. This computer will save the audio to disk. The audio that is to be saved will consist mostly of spoken communication. The saved audio is to be used in a framework for modeling and visualization. There are three major problems involved in designing a software to fill this purpose: recording both input and output audio at the same time, efficiently receiving multiple audio-streams at once and designing an interface where finding and organizing the computers to record audio from is easy. The software developed to solve these problems consists of two parts; a server and a client. The server captures the input (microphone) and output (speaker) audio from a computer. To capture the output and input audio simultaneously an external application named Virtual Audio Cable (VAC) is used. The client connects to multiple servers and receives the captured audio. Each one of the client’s server-connections is handled by its own thread. To make it easy to find available servers an Automatic Server Discovery System has been developed. To simplify the organization of the servers they are displayed in a tree-view specifically designed for this purpose.

Entertainment is an ever-changing medium, and television specifically has gone through many technological innovations since its bright beginnings. These innovations have consistently changed the way stories are told. Stylistic shifts in key elements ranging from shot format to the way shows are constructed can be seen especially clearly in horror which does not have the same narrative constraints as many other genres, and therefore more room to experiment. By tracking changes in the narrative formats of serialized and anthology horror shows, I define a new era of television brought about by the prevalence of streaming, and the rise of binge culture.