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Design and implementation of distributed programmable media gateways.

机译：分布式可编程媒体网关的设计与实现。

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摘要

Multicasting multimedia streams over the Internet is problematic due to network and host heterogeneity. One of the proposed solutions is to place media gateways inside the network to adopt the media streams for different links and hosts.; In this dissertation, we investigate several novel extensions to the existing model of media gateways. First, we make the gateways user extensible by allowing injection of Tcl code that specifies transformations on the media streams. Second, we improve efficiency in bandwidth consumption by adaptively running the transformations at strategic locations on the Internet. We further reduce bandwidth consumption and improve throughput by decomposing a transformation into multiple sub-transformations for execution on different gateways, forming a data flow pipeline. To realize these extensions, we have designed, implemented, and simulated several components of the media gateways.; We designed and implemented Dali, a low-level software library for building high-performance, predictable, highly extensible and computationally intensive multimedia applications. We designed Dali based on a set of design principles that is different from previous media processing libraries. We sacrificed ease of use for performance. We exposed the underlying structure of the media data (such as DCT blocks and motion vectors), forced explicit resource control, and promoted sharing of memory. As a result, programs written in Dali are fast, more predictable and highly re-configurable. Dali serves as a case study in API design for high performance media processing libraries.; We built a prototype of a programmable, application-level media gateway, called Degas. Using an event-driven, descriptive programming model, users can write simple programs, called deglets, that can be uploaded into the gateway to perform operations on input video frames. We perform per-operation optimization by mapping a high-level API to low-level Dali code. Our prototype serves as a framework where many research issues about the design of programmable media gateways can be explored.; We designed, simulated, and implemented AGLP, which is an application-level protocol for choosing strategically located Degas gateways on a wide-area network to run deglets. AGLP minimizes bandwidth consumption, and is able to adapt to a changing network environment by migrating deglets. We use the announce/listen paradigm and multicast damping to achieve robustness and scalability. Our experimental results show that AGLP is able to scale up to a large number of gateways on the network.; Finally, we investigated a mechanism for distributing a deglet onto multiple gateways. By modelling a deglet as a tree of operations, we use a linear time algorithm to decompose a deglet into multiple subdeglets. We also extended AGLP to locate helper gateways to run these sub-deglets. These sub-deglets form a pipeline where video streams can flow through. Our experiment results shows that we are able to improve thoughput and quality over a bottleneck gateway, without compromising the scalability of AGLP.
机译：由于网络和主机的异构性，在Internet上组播多媒体流存在问题。所提出的解决方案之一是将媒体网关放置在网络内部，以将媒体流用于不同的链路和主机。在本文中，我们研究了对媒体网关现有模型的几种新颖扩展。首先，通过允许注入Tcl代码来指定媒体流上的转换，使网关用户可扩展。第二，我们通过在Internet上的战略位置自适应运行转换来提高带宽消耗的效率。通过将转换分解为多个子转换以在不同网关上执行，我们进一步减少了带宽消耗并提高了吞吐量，从而形成了数据流管道。为了实现这些扩展，我们设计，实现和模拟了媒体网关的几个组件。我们设计并实现了Dali，这是一个底层软件库，用于构建高性能，可预测，高度可扩展且计算密集的多媒体应用程序。我们根据与以前的媒体处理库不同的一组设计原则设计了Dali。我们牺牲了易用性来提高性能。我们公开了媒体数据的基础结构（例如DCT块和运动矢量），强制的显式资源控制和促进的内存共享。因此，用Dali编写的程序是快速，更可预测的且高度可重新配置的。 Dali作为高性能媒体处理库的API设计案例研究。我们构建了一个称为Degas的可编程，应用程序级媒体网关的原型。使用事件驱动的描述性编程模型，用户可以编写称为deglet的简单程序，这些程序可以上载到网关以对输入视频帧执行操作。我们通过将高级API映射到低级Dali代码来执行每个操作的优化。我们的原型作为一个框架，可以探讨许多有关可编程媒体网关设计的研究问题。我们设计，模拟并实现了AGLP，这是一种应用程序级协议，用于选择在广域网中策略性地定位的Degas网关来运行deglet。 AGLP最大限度地减少了带宽消耗，并能够通过迁移deglet来适应不断变化的网络环境。我们使用公告/监听范例和多播阻尼来实现鲁棒性和可伸缩性。我们的实验结果表明，AGLP可以扩展到网络上的大量网关。最后，我们研究了一种将deglet分发到多个网关的机制。通过将deglet建模为操作树，我们使用线性时间算法将deglet分解为多个子deglet。我们还扩展了AGLP，以定位帮助程序网关来运行这些子Deglet。这些子dedeglet构成了视频流可以流过的管道。我们的实验结果表明，我们能够通过瓶颈网关提高吞吐量和质量，而不会影响AGLP的可伸缩性。

著录项

  • 作者

    Ooi, Wei Tsang.;

  • 作者单位

    Cornell University.;

  • 授予单位 Cornell University.;
  • 学科 Computer Science.
  • 学位 Ph.D.
  • 年度 2001
  • 页码 149 p.
  • 总页数 149
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 自动化技术、计算机技术;
  • 关键词

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