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题名:
基于宽带接入的实时视频服务关键技术研究
作者: 张源海
答辩日期: 2008-05-29
授予单位: 中国科学院软件研究所
授予地点: 软件研究所
学位: 博士
关键词: 实时视频服务 ; 流媒体 ; 发送速率控制 ; 服务器资源分配
其他题名: Research on Key Techniques of Real-time Video Service based on Broadband Access Network
摘要: 随着宽带网络和多媒体技术的发展,在Internet上提供实时视频服务成为可能。然而,当前的Internet网络以尽力而为(Best-effort)的方式提供数据传输,带宽波动、延迟抖动和丢包等现象时有发生。为了保证实时视频服务的质量,必须采用有效的速率控制和资源调度策略。本文概述了目前实时视频服务面临的挑战,简要介绍了与实时视频服务相关的研究领域和技术亮点,重点研究了在端到端的流媒体系统中保证实时视频服务质量的技术,主要取得了以下几个方面的研究成果: 第一、提出了一种基于PCR协助的细粒度速率控制方法。该方法通过PCR提供的时间信息计算细粒度的发送时间戳,使得系统对发送速率的调整更加精细,从而有效地解决了传统方法在传输高清视频流时的问题,同时利用信道辅助填充策略提高了并发高清视频流的数量。实验结果表明,该方法能明显地改善多路并发高清视频流的播放质量。 第二、提出了支持大规模视频传输的媒体服务器资源分配算法。该算法建立在基于组播方式的媒体服务器传输体系结构基础上,通过对服务器资源变量的数学建模和推导,把磁盘和内存资源的分配问题转化为经典的线性规划问题,然后引入前缀缓存机制对模型进行了扩展。实验结果表明,该算法能更高效地利用系统的资源,在特定的服务器配置下,可以有效地增加并发视频流数量。 第三、提出了支持交互式操作的大规模视频分发策略。该策略结合传统的支持交互式操作的方法,一方面利用单独信道支持交互式操作,另一方面选择性地动态预取合适的视频段,以便减少单独信道的启动时间。实验结果表明,该策略有效地减小了交互式操作过程中发生阻塞的概率,提高了系统资源利用率,从而能在基于组播或广播的流媒体系统中提供高效的交互式服务。 第四、设计并实现了一组应用于用户驻地网的实时视频服务质量保障技术,内容包括适于海量媒体文件的磁盘读取策略、服务端自适应缓冲策略、基于时间戳的数据包封装策略、服务端流量控制策略、客户端缓冲调整策略等。这些技术具有较强的实用性,系统测试和实际应用的结果表明,通过这些技术可以使用户驻地网的用户享受到高质量、大规模的实时视频服务。
英文摘要: Recent developments in high-speed network and multimedia technology have made it possible to provide real-time video service over Internet. However, current Internet is a best-effort network where loss, variable delays and bandwidth jitter occur frequently during data transmission. Therefore, in order to ensure the quality of real-time video service, effective rate control and resource scheduling mechanisms should be used. In this dissertation, the challenges of real-time video service are firstly summarized, which is followed by a brief description of the research areas and novel techniques related with real-time video service. Then special emphasis is focused on research of techniques that can ensure the quality of video service. The main contribution and innovation points are as follows: Firstly, a refined PCR-assist rate control approach is proposed. It uses the timing information calculated by PCRs to regulate transmission rate in a refined way, which makes the decided rate reflect the variation of video streams in a more detailed fashion and reduces the difference between the decided rate and the real bit rate. Compared with traditional solutions, it is more effective especially when HD stream is transmitted. In addition, we have also proposed a channel-assist padding mechanism, which can increase the number of concurrent HD streams. The experimental results show that our proposed approach can remarkablely improve the playback quality of concurrent HD streams. Secondly, a resource allocation algorithm in media server for supporting large-scale video transmission is proposed. Based on a multicast-based media server architecture, we use mathematical analysis to formulate and solve a linear programming problem whose solution provides insights into the server’s memory and disk resources allocation. At the same time, prefix caching is introduced to extend the architecture and enhance the performance of media server. The experimental results show that our proposed algorithm can use the system resources more effectively and support more concurrent videos than traditional methods. Thirdly, a large-scale video transmission strategy for supporting interactive functions is proposed. On one hand, it uses interactive channels to support interactive functions that can not be served by local buffer. On the other hand, it prefetches the appropriate video segments selectively, which can reduce the opening time of interactive channels. The experimental results show that our proposed strategy can reduce the usage of server resources and the block probability during interactive operations, which means that interactive functions can be served better in the multicast-based streaming system. Fourthly, a series of mechanisms, which can ensure the quality of real-time video service in Customer Premises Network, are designed and implemented. These mechanisms include disk retrieve strategy suited to huge amount of media data, server-side self-adapting buffer strategy, packet encapsulation strategy based on timestamp, server-side traffic control strategy, receiver buffer management strategy, etc. These mechanisms are easy to be carried out and the results of system test and actual application show that users of Customer Premises Network can be provided with high-quality and large-scale real-time video service by the above mechanisms.
语种: 中文
内容类型: 学位论文
URI标识: http://ir.iscas.ac.cn/handle/311060/5884
Appears in Collections:中科院软件所

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Recommended Citation:
张源海. 基于宽带接入的实时视频服务关键技术研究[D]. 软件研究所. 中国科学院软件研究所. 2008-05-29.
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