Architictures for Digital Multimedia On-Demand Services in Integrated Networks

集成网络中数字多媒体点播服务的体系结构

• 批准号: 9217260
• 负责人: Venkat Rangan
• 金额: $ 25.2万
• 依托单位: University of California-San Diego
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1993
• 资助国家: 美国
• 起止时间: 1993-07-01 至 1997-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9217260&HistoricalAwards=false
• 关键词: Architictures; Digital; Multimedia; Demand; Services

Further advances in networking coupled with rapid advances in storage technologies will make it feasible to build multimedia on-demand servers capable of providing services similar to those of a neighborhood videotape rental store on a metropolitan-area network. In this research we investigate architectures for multimedia servers that can permit multiple subscribers to interactively record and playback multimedia objects over integrated computer networks. We address two main requirements in the development of such a multi-subscriber multimedia server: (1) Continuity of playback of each media constituting a multimedia object, and (2) mutual synchrony of playback of the different media constituting a multimedia object. In order to address the continuity requirement, we develop admission control algorithms with which a multimedia server can satisfy the maximum number of subscribers simultaneously without violating continuity of playback for any of them. One such algorithm is a quality proportional scheme that retrieves media units at a rate proportional on an average to their respective playback rates, but uses a staggered toggling technique by which successive numbers of media blocks retrieved are fine tuned individually to admit and service an optimal number of subscribers simultaneously. Initial performance estimation shows that the quality proportional policy is an order of magnitude more scalable compared to straightforward admission control policies such as servicing one subscriber per disk head and round robin servicing of subscribers. During retrieval of a multimedia object, mediaphones that playback the different media components of the object may have recording and playback rate mismatches. Furthermore, emerging integrated networks such as ATM are expected to introduce jitter that can nevertheless be bounded in the transport of media units from servers to mediaphones. In order to ensure synchronous playback of multimedia objects, we study a feedback technique in which a multimedia server uses lightweight messages called feedback units generated by mediaphones and transmitted back to the server to detect asynchronies during playback. We study various resynchronization policies such as aggressive, conservative, and probabilistic and compare their performance for video/audio playback. Initial performance estimation shows that whereas aggressive policies are expected to perform best only at lower playback rates, conservative policies are expected to perform best only at higher playback rates. In contrast, probabilistic policies have the potential to perform uniformly well at all playback rates. The policies and algorithms developed in this project form the basis for a prototype multimedia server being developed at the UCSD Multimedia Laboratory.

网络的进一步发展和存储技术的快速发展将使建立多媒体点播服务器成为可能，该服务器能够提供类似于城域网络上的社区录像带租赁商店的服务。在这项研究中，我们研究了多媒体服务器的体系结构，它可以允许多个订户在集成的计算机网络上交互地记录和回放多媒体对象。我们解决了这种多订户多媒体服务器的开发中的两个主要要求：(1)构成多媒体对象的每个媒体的回放的连续性，以及(2)构成多媒体对象的不同媒体的回放的相互同步。为了解决连续性的要求，我们提出了允许多媒体服务器同时满足最大用户数量的接纳控制算法，而不会破坏任何一个用户的播放连续性。一种这样的算法是质量比例方案，其以与媒体单元各自的重放速率成比例的平均速率检索媒体单元，但是使用交错切换技术，通过该技术，检索的连续数量的媒体块被单独微调以同时接纳和服务最优数量的订户。初步性能评估表明，与简单的接纳控制策略相比，质量比例策略的可扩展性更高一个数量级，例如为每个磁头一个用户提供服务和为用户提供循环调度服务。在检索多媒体对象期间，回放该对象的不同媒体分量的传送器可能具有记录和回放速率不匹配。此外，新兴的集成网络，如ATM，预计会引入抖动，但在将媒体单元从服务器传输到中继器的过程中，抖动可能会受到限制。为了确保多媒体对象的同步回放，我们研究了一种反馈技术，其中多媒体服务器使用由中继器生成的称为反馈单元的轻量级消息来检测回放过程中的异步。我们研究了各种再同步策略，如积极的、保守的和概率的，并比较了它们在视频/音频播放中的性能。初步的性能评估显示，虽然激进策略预计仅在较低的回放速率下执行得最好，而保守策略预计仅在较高的回放速率下执行得最好。相比之下，概率策略有可能在所有回放速率下都执行得很好。该项目中开发的策略和算法构成了加州大学圣迭戈分校多媒体实验室正在开发的原型多媒体服务器的基础。