Idag finns som alltid behovet att distribuera media. Allt eftersom prestandan för överföring av information i dator-nätverk har ökat har detta blivit möjligt genom streaming, strömmande media. Detta innebär att klienten inte behöver ladda ner hela materialet för att kunna se eller lyssna på det. Allt eftersom kravet på kvalitén av materialet ökar blir kraven på nätverket högre. Precisallt Media AB är ett företagsom sysslar med digital skyltning. För att nå ut med film till sina skyltar som finns i olika butiker och varuhus, schemaläggs och skickas film till en vanlig pc som sköter skylten. Lagring av video sker lokalt, det vill säga materialet som spelas upp på en skylt är lagrat på samma dator som spelar upp det. Detta är ingen effektiv lösning eftersom överföringen av material som sker över Internet måste ske till varje dator som ska spela upp det. Går det att skapa en effektivare lösning genom att använda streaming hos kunden? Och går det att effektivisera distribueringen av media tillkundens nätverk?

Streaming applications like multimedia and radar signal processing applications are becoming increasingly compute-intensive. To overcome the computational demands new parallel architectures are emerging.   The programming tools provided with these architectures require low-level programming, which creates a need for a common high-level architecture independent language that can exploit parallelism efficiently. One such language is StreamIt, designed around the notions of streams and stream transformers, which allows efficient mapping to a variety of architectures.   The overall goal of this master’s thesis is to evaluate the StreamIt language from a programmability and portability point of view. An MPD-application has been developed in StreamIt, which is executed on the RAW simulator. Furthermore, a code generator is designed to compile and execute the application on the XPP simulator.   The conclusions drawn are that StreamIt is easy to learn, but hard to use because of its programming paradigm as compared to conventional languages. StreamIt programming involves thinking in terms of streams instead of globally accessed memory. The structure of StreamIt makes it easy to reuse components and modify the application. The construction of the compiler makes it possible to port StreamIt application to various architectures.

Recent studies have shown that, in a sufficiently deep gas-solid fluidized bed of Geldart A particles, gas streaming may occur allowing gas to bypass a large portion of the particle bed. Since this is a newly observed phenomenon in fluidized beds, there is uncertainty and lack of information about the various aspects of the streaming flow. The objective of the current project is to investigate the streaming phenomenon with a combination of experimentation and modeling. In the experimental part, pressure fluctuations as a measure of the fluidized bed hydrodynamics were used to study the influence of different parameters on the behavior of a deep fluidized bed. Pressure fluctuations have been measured at 8 axial locations from 4 to 150 cm above the gas distributor for bed depths and gas velocities ranging from 0.4 to 1.6 m and 0.04 to 0.20 m/s (equal to 10 to 50 times minimum fluidization velocity), respectively. Two particle size distributions with Sauter mean diameters of 48 µm and 84 µm and two distributor plates with differing percentage open area were also tested for each bed depth and gas velocity. Analysis of pressure fluctuations in the time and frequency domains, in combination with visual observations revealed that streaming flow emerges gradually at bed depths greater than 1 m. Increased gas velocity and fines content act to delay the onset of streaming, but can not completely eliminate it over the range of velocities examined. The two different distributor designs had no measurable effect on the streaming flow. The results of this study are provided in the first section of the present report.<p> In order to further investigate the nature of streaming flow, several cases of forced streams and jetting flows were designed and conducted, in addition to the natural streaming flow in deep beds. Results indicated that the natural streaming most closely resembles the imposed stream which not only the imposed stream, but additional gas added through the distributor. The case of jet flows with no additional gas resembles the severe streaming that might happen in very deep beds with the existence of completely non-fluidized regions. Application of supporting jets in addition to the main gas flow could enhance the fluidization quality to some extent, however, not enough to provide a normal fluidization. Wavelet analysis of the pressure fluctuations showed that in deep fluidized beds, bubbling activity with the typical dominant frequency coexist with the streaming flow, with a minor contribution. Wavelet findings suggested that the streaming flow can be considered to form by increasing the relative importance of one available stream of bubble activity with increasing bed depth. The results of this study are provided in the second section of this report. Further study of the streaming flow was undertaken with computational fluid dynamic (CFD) simulation of the deep fluidized bed. CFD simulation of fine Geldart A particles has met with challenges in the open literature and various modifications have been proposed to be able to model fluidized beds of these particles. In the present work, the commercial CFD codes FLUENT and MFIX were initially tested for the modeling of deep fluidized bed of Geldart A particles. However, simulation results did not show any sign of streaming flow in the fluidized bed. Subsequently, the commercial CFD code BARRACUDATM that has been claimed by the developers to be appropriate for this purpose, was tested. Due to the lack of data on the performance of this code, a simple case of modeling a freely bubbling fluidized bed of Geldart A particles was attempted first. For this purpose, four different simulation cases, which included three different numerical grid sizes and two drag models with a realistic particle size distribution were designed and tested. The simulated bed expansion, bubble size distribution, rise velocity and solid fraction were compared with commonly accepted correlations and experimental data from the literature. The results showed a promising predictive capability of the code without the need for modifying the drag model or other constitutive relations of the model. The third section of the report presents the simulation results of this study.<p> The BARRACUDA code was then used for simulating the deep fluidized bed of Geldart A particles. However, similar to the previous CFD codes tested, instead of streaming flow, bubbling fluidization was predicted. Therefore, a phenomenological model was developed to better understand the streaming flow. According to the model results, the stream represents a zone of much lower pressure drop compared to other parts of the bed, which can be a possible reason for the formation and stability of the streaming flow inside the fluidized bed. The model results showed that increasing the bed depth enhances the streaming flow, while increasing the gas velocity improves the uniformity of the bed and decreases the streaming severity. Streaming flow was found to be less severe for larger particle sizes. All of these trends are in conformity with the experimental results. These findings provide the content of the fourth and final section of this report.

The objectives of this thesis are to investigate the challenges on video streaming, to explore and compare different video streaming mechanisms, and to develop video streaming algorithms that maximize visual quality. To achieve these objectives, we first investigate scalable video multicasting schemes by comparing layered video multicasting with replicated stream video multicasting. Even though it has been generally accepted that layered video multicasting is superior to replicated stream multicasting, this assumption is not based on a systematic and quantitative comparison. We argue that there are indeed scenarios where replicated stream multicasting is the preferred approach. We also consider the problem of providing perceptually good quality of layered VBR video. This problem is challenging, because the dynamic behavior of the Internet's available bandwidth makes it difficult to provide good quality. Also a video encoded to provide a consistent quality exhibits significant data rate variability. We are, therefore, faced with the problem of accommodating the mismatch between the available bandwidth variability and the data rate variability of the encoded video. We propose an optimal quality adaptation algorithm that minimizes quality variation while at the same time increasing the utilization of the available bandwidth. Finally, we investigate the transmission control protocol (TCP) for a transport layer protocol in streaming packetized media data. Our approach is to model a video streaming system and derive relationships under which the system employing the TCP protocol achieves desired performance. Both simulation results and the Internet experimental results validate this model and demonstrate the buffering delay requirements achieve desired video quality with high accuracy. Based on the relationships, we also develop realtime estimation algorithms of playout buffer requirements.

In this paper, we propose an early retransmission scheme to improve TCP's performance in delivering time-sensitive media. Our extensive ns2 simulations show significant improvement. When integrated into a traditional TCP variant, namely TCP-SACK, the early retransmission scheme can substantially reduce the latency caused by retransmission timeout. As a result, it can help TCP-SACK achieve a considerably higher success rate in delivering real time media. Early Retransmission also enhances the performance of a delay-based TCP variant, namely PERT. Furthermore, we also explore the improvement brought by employing a fine-grained retransmission timer, and compare it with ER. We find out that ER outperforms the fine grained timer in a variety of conditions and the combination of the two can further improve performance.

As the success of P2P file sharing systems such as BitTorrent and eMule, P2P has become a promising technology to provide video streaming services over the Internet. The P2P technology is shown to be capable of significantly reducing the transmission overhead of video server. However, due to the dynamic nature of peers, a P2P streaming system suffers from bursty packet loss caused by peer departures. Furthermore, as the packet being forwarded peer by peer, the situation becomes worse and worse. This problem is recognized as packet loss accumulation problem. To overcome bursty packet loss and eliminate packet loss accumulation problems caused by peer departures in P2P streaming systems, a multi-source structure combining with a distributed FEC scheme for P2P streaming systems is proposed. In the proposed structure, each peer connects to multiple parents according to the pre-specified FEC packets ensemble and each parent forwards partial streaming packets to the peer. If one or few parents fail, other parents can still provide most of remaining part of streaming packets that can be used to recover the missing packets by using packet level FEC scheme. To evaluate the performance of P2P streaming systems using the proposed multi-source structure, we first propose a Continuous-Time Markov Chain to model the arrival/departure behavior of parents in P2P systems. Based on the Markov Chain, we further derived equations to calculate packet loss probabilities for both single-source and multi-source P2P systems. The mathematical analyses show how the packet loss accumulation occurs in P2P systems and how the proposed multi-source structure eliminates packet loss accumulation problem. In addition, simulations are conducted using NS2 to evaluate the proposed multi-source structure. Simulation results verify that the proposed multi-source structure combining with an appropriate FEC protection is capable of overcoming burst packet loss and eliminating packet loss accumulation problems. The simulation results also show that the proposed multi-source structure performs better than the single-source and the PROMISE/CollectCast P2P systems in terms of packet loss, end-to-end delay, and PSNR. A prototype system is implemented to conduct a real experiment over the Internet to validate the effectiveness of the proposed scheme.

Traditional peripheral displays rely on drawing the user's attention and gaze through alerts. These displays function best when the central task does not require the user's constant attention. For tasks that require a user to always maintain focus, alert-based displays are not appropriate. We assert that conveying information to a user without drawing his gaze, allows the user to maintain constant focus on his primary task while still receiving additional information. In this thesis we use video games to examine streaming peripheral displays as a means of presenting information without drawing gaze. The results of our experiments showed no significant difference between user performance using our display encoded for peripheral viewing versus an unencoded display. Additionally, we found that players were successfully able to perceive information shown on a streaming peripheral display, however, as game difficulty increased the effectiveness of the streaming peripheral display decreased. Finally, we show that as game level increases, users adopt risk-tolerant strategies. Drawing from these results, we have suggested some additional heuristics pertaining to streaming peripheral displays. Moreover, we have suggested further situations where streaming peripheral displays may be useful. / Thesis (Master, Computing) -- Queen's University, 2009-01-28 10:41:41.602

Thesis (M.Sc.)--University of Alberta, 2010. / Title from PDF file main screen (viewed on Apr. 13, 2010). A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master of Science in Digital Signals and Image Processing, Department of Electrical and Computer Engineering, University of Alberta. Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2003. / Vita. Includes bibliographical references. Available also from UMI Company.

Thesis (M.S.)--West Virginia University, 2002. / Title from document title page. Document formatted into pages; contains iii, 46 p. Includes abstract. Includes bibliographical references (p. 43-46).