流媒体应用中关键技术的研究探析

本文从流媒体应用支持该的流媒体编码技术和网络技术两个角度出发,针对其面临的挑战,深入、全面的综述了编码技术与网络技术的发展与现状,并指出了大规模流媒体应用中关键技术的研究方向.     

DirectShow技术在网络编程中的应用

Internet的迅速发展使各种各样的网络多媒体应用层出不穷,其中流媒体应用发展最为迅速,流媒体技术的目的在于缩短客户对多媒体数据回放的等待时间和为用户提供较好的服务质量.文中论述了流媒体技术、原理,并详细介绍了一个如何把DirectShow技术和Windows Socket技术相结合,用流媒体技术来实现媒体信息在网络中的传输和实时观看的解决方案.     

多媒体网络:从内容分发网络到未来互联网

近年来,随着网络技术的飞速发展,互联网流量视频化的趋势日益明显,视频应用使互联网的可扩展性、可演进性、服务质量和网络安全面临诸多挑战.内容分发网络通过在应用与网络间构建覆盖网,为解决网络视频应用面临的分发难题提供了有力的支持,也成为当前网络视频产业中的关键技术.但是随着视频应用在移动性、交互性、异构性以及可扩展性方面需求的不断增长,现有内容分发网络技术面临重大挑战,学术界与工业界都试图从互联网体系架构入手解决网络视频应用中的问题.文中系统总结了内容分发技术面临的挑战以及现有互联网体系结构研究的思路与核心技术,提出了面向未来网络的多媒体网络设计思路.     

基于P2P的流媒体技术

现有的流媒体系统一般是基于客户／服务器模式和IP组播技术,这限制了用户数量且IP组播需先得到ISP支持,故其发展受到很大限制。而在P2P网络中,每个接收数据的用户同时向外转发数据,这就充分利用了以往忽视的客户机资源。首先指出了P2P流媒体应用中所面临的挑战,并着重从应用层多播树、网络异构性、激励机制等方面阐述了P2P流媒体的研究现状,分析讨论了存在的问题,最后指出进一步的研究方向。     

大规模流媒体传输技术的发展

随着流媒体与网络技术的飞速发展,人们对视频会议、视频点播、远程教学、在线游戏和娱乐等应用的需求越来越广泛,大规模流媒体技术是使这些应用得以迅速发展的关键。该文从网络传输技术角度出发,针对其面临的挑战,深入,全面地综述了各种网络传输技术的发展与现状,以及发展的趋势。     

一种分层P2 P流媒体系统重叠网的构建策略

基于Peer-to-Peer(P2P)技术的流媒体应用具有部署效率高及可扩展性好等突出优势。而采用分层视频编码技术的P2P流媒体系统把原视频流分解为多个视频层数据进行分发,让节点能够选择与自己带宽资源相匹配的视频质量,使其很好地适应节点的异构性。但是各分层视频数据传输的路径存在较大差异,使重叠网构建策略面临更大的挑战。因此定义了基于分层视频编码技术环境下的P2P流媒体重叠网络构建问题,并证明该问题是一个NP难问题。提出了一种构建重叠网的集中启发式算法,同时还提出了一种基于视频组(Streaming Group)的分布式重叠网络构建策略。通过大规模网络仿真实验验证了基于该分布式重叠网构建策略的分层流媒体系统具备低服务器带宽占用、高数据获取率等优点。     

DirectShow技术在网络编程中的应用

Internet的迅速发展使各种各样的网络多媒体应用层出不穷,其中流媒体应用发展最为迅速,流媒体技术的目的在于缩短客户对多媒体数据回放的等待时间和为用户提供较好的服务质量。文中论述了流媒体技术、原理,并详细介绍了一个如何把DirectShow技术和WindowsSocket技术相结合,用流媒体技术来实现媒体信息在网络中的传输和实时观看的解决方案。     

一种异构无线网络流媒体QoS评测系统的设计实现

异构无线网络接入技术的发展为移动流媒体技术应用带来了全新的机遇与挑战.流控制传输协议SCTP(Stream Control Transmission Protocol)的提出能够很好地实现异构无线网络间的透明无缝切换.为了研究未来泛在异构无线网络环境中的视频传输,设计了一种SCTP多宿环境下的流媒体QoS评测系统.实验结果表明,该方案能在异构无线网络环境下对不同网络拥塞和负载下的视频传输行为和服务质量进行有效的分析.     

基于CDN的流媒体分发技术研究综述

随着网络技术的高速发展,Internet用户飞速增长,网络拥塞、服务器负载过重、访问延迟过大等问题一直困扰着用户。CDN(ContentDistributionNetwork———内容分发网络)的出现极大改善了Internet的访问速度和服务质量。但是,流媒体内容的日益流行又对CDN技术提出了新的挑战。文章详细阐述了在CDN条件下,基于代理缓存机制,对流媒体进行智能分发技术的研究现状,详细描述了流媒体在主干网中的分发传输和它们之间的协作过程。     

CDN网络关键技术研究

CDN(Content Delivery Networks)网络是在现有的Internet中增加一层新的网络架构,将网站的内容发布到最接近用户的网络"边缘",可以使流媒体内容在网络中有效分送,缓解服务器负载、减轻网络拥塞、加快用户访问网站的响应速度,从整体上大幅度提高流媒体传输的服务质量.本文分析了CDN的网络体系结构和工作流程,重点讨论了CDN网络实现的关键技术.随着宽带网络的发展,CDN技术的相关应用必将成为未来高速网络的主流应用之一.     

Adaptive interface selection over cloud-based split-layer video streaming via multi-wireless networks

As mobile devices such as tablet PCs and smartphones proliferate, the online video consumption over a wireless network has been accelerated. From this phenomenon, there are several challenges to provide the video streaming service more efficiently and stably in the heterogeneous mobile environment. In order to guarantee the QoS of real-time HD video services, the steady and reliable wireless mesh is necessary. Furthermore, the video service providers have to maintain the QoS by provisioning streaming servers to respond the clients’ request of different video resolution. In this paper, we propose a reliable cloud-based video delivery scheme with the split-layer SVC encoding and real-time adaptive multi-interface selection over LTE and WiFi links. A split-layer video streaming can effectively scale to manage the required channels on each layer of various client connections. Moreover, split-layer SVC model brings streaming service providers a remarkable opportunity to stream video over multiple interfaces (e.g. WiFi, LTE, etc.) with a separate controlling based on their network status. Through the adaptive interface selection, the proposed system aims to ensure the maximizing video quality which the bandwidth of LTE/WiFi accommodates. In addition, the system offers cost-effective streaming to mobile clients by saving the LTE data consumption. In our system, an adaptive interface selection is developed with two different algorithms, such as INSTANT and EWMA methods. We implemented a prototype of mobile client based on iOS particularly by using iPhone5S. Moreover, we also employ the split-layer SVC encodes in streaming server-side as the add-on module to SVC reference encoding tool in a virtualized environment of KVM hypervisor. We evaluated the proposed system in an emulated and a real-world heterogeneous wireless network environments. The results show that the proposed system not only achieves to guarantee the highest quality of video frames via WiFi and LTE simultaneous connection, but also efficiently saves LTE bandwidth consumption for cost-effectiveness to client-side. Our proposed method provides the highest video quality without deadline misses, while it consumes 50.6% LTE bandwidth of ‘LTE-only’ method and 72.8% of the conventional (non-split) SVC streaming over a real-world mobile environment.     

Rate-sensitive leverage of QoS and QoP for ubiquitous video streaming via buffer-aware feedback control

Providing real-time Internet video streaming anytime, anywhere and using any devices from different access networks preserves more challenges to equilibrate the quality of service (QoS) and security protection (QoP). Because encryption/decryption for video packets are time-consuming processes to protect real-time video streaming services from eavesdropping, our observation is that the playback buffer occupancy (PBO) can simply indicate time availability to adjust security level to affect the packet sending rate. In this paper, we present an end-to-end buffer-aware feedback control from client PBO for effectively securing media streaming for heterogeneous clients over ubiquitous Internet. That is, security-level adjustments can be applied further to keep PBO running away from overflow and underflow to pursue an effective leverage between QoS and QoP. To further boost the protection, we also apply the Diffie-Hellman key negotiation method to provide the dynamic key changes. Moreover, since the running PBO will vary on the dynamics of Internet from access time, client devices and access networks, the different applied security levels and key changes during the video streaming session will make eavesdropper more difficult to recover all the encrypted videos delivered in public networks. We demonstrate the leverage performance in preserving both QoS and QoP for ubiquitous video streaming in our proposed schemes by comprehensive experiments on a true VoD system. The experimental results show our secure VoD scheme can achieve cost-effective leverage of QoS and QoP from different inserted network dynamics, even if client buffer size is limited to 256 KB only.     

混合底层拓扑网络中的P2P流媒体模型研究

网络不断演进会改变底层IPv4/IPv6的基础结构。主要讨论在这样的混合网络环境下部署和应用P2P流媒体的关键问题。提出了采用分层思想设计一个完整的P2P流媒体系统模型,该模型在考虑混合底层网络拓扑环境的情况下同时引入了P2P安全认证的机制,在有效提升流媒体分发效率的同时保证了安全性。仿真结果表明,该模型更能满足未来网络演进过程中混合拓扑环境下P2P应用的需要,并具有良好的安全性。     

网络视频流识别技术研究

互联网多媒体技术已经成为我们日常生活中不可或缺的元素之一,人们可以通过网络视频观看电影、电视剧,还可以通过网络视频聊天,通过网络视频学习和召开视频会议,网络视频应用越来越频繁,这使得网络流媒体数据量不断增大,因此增加了网络带宽和网络传输质量的负担。本文对目前网络视频传播形式进行研究,发现目前主流的网络视频通信为P2P和Web,由此对二者的通信方式、视频流识别方法进行研究,以提高网络视频流识别能力,提高视频服务质量。     

Content-adaptive wireless streaming of instructional videos

Video streaming over wireless networks is becoming increasingly important for a variety of applications. To accommodate the dynamic change of wireless network bandwidths, Quality of Service (QoS) scalable video streams need to be provided. This paper presents a system of content-adaptive streaming of instructional (lecture) videos over wireless networks for E-learning applications. We first provide a real-time content analysis method to detect and extract content regions from instructional videos, then apply a “leaking-video-buffer” model to adjust QoS of video streams dynamically based on video content. In content-adaptive video streaming, an adaptive feedback control scheme is also developed to transmit properly compressed video streams to video clients not only based on network bandwidth, but also based on video content and the preferences of users. Finally, we demonstrate the scalability and content adaptiveness of the proposed video streaming system with experimental results on several instructional videos.     

Content-adaptive wireless streaming of instructional videos

Video streaming over wireless networks is becoming increasingly important for a variety of applications. To accommodate the dynamic change of wireless network bandwidths, Quality of Service (QoS) scalable video streams need to be provided. This paper presents a system of content-adaptive streaming of instructional (lecture) videos over wireless networks for E-learning applications. We first provide a real-time content analysis method to detect and extract content regions from instructional videos, then apply a “leaking-video-buffer” model to adjust QoS of video streams dynamically based on video content. In content-adaptive video streaming, an adaptive feedback control scheme is also developed to transmit properly compressed video streams to video clients not only based on network bandwidth, but also based on video content and the preferences of users. Finally, we demonstrate the scalability and content adaptiveness of the proposed video streaming system with experimental results on several instructional videos.     

下一代因特网QoS路由机制的研究

目前得到广泛应用的因特网是一种尽力而为服务模式的网络,它不能对网上实时多媒体业务提供服务质量保证,传统的路由选择、流量控制与重传机制具有不可预测的时延特性,对时延敏感的媒体信息传输极为不利。随着多媒体应用领域的拓展和网上通信的日益增多,QoS路由越来越成为目前网络研究的热点。文中针对下一代因特网的综合服务模型与区分服务模型的QoS路由机制做了较详尽的探讨,分析了QoS路由算法的研究现状,并探讨了将来的研究方向。     

面向流媒体传输的Edge-to-Edge网络体系结构

随着网络技术的发展,互联网研究从单纯的数据交换转移到应用服务。传统的端到端网络体系结构存在许多缺陷,如缺乏资源可控性、无法保证QoS等,不适合传输海量流媒体数据。P2P等应用虽然缓解了服务器的压力,但损害了ISP的利益。本文提出面向流媒体应用的Edge-to-Edge网络体系结构,通过将核心网络和边缘网络隔离,在边缘网络节点中增加存储和计算能力来提高网络性能。分析了构建这种网络体系结构的关键技术。模拟结果表明,Edge-to-Edge网络体系结构能有效减少用户启动延时,极大减少核心网络带宽。     

基于P2P网络的大规模视频直播系统

介绍了一种基于P2P(peer-to-peer)网络的大规模视频直播系统Gridmedia.该系统采用Gossip协议构建无结构的应用层覆盖网络,每个节点可以独立地选择自己的伙伴节点.在覆盖网络上,每个节点通过一种推拉结合的流传输策略从邻居节点获取数据.与DONet中的纯拉策略相比,推拉结合策略大幅度减小了终端用户观看视频的延迟,并有效降低了直播系统的控制开销.PlanetLab上的大量实验充分表明了该策略的有效性.Gridmedia的原型系统通过300Kbps的视频码流对2005年春节联欢晚会进行了全球互联网直播.晚会期间,全球范围内有超过500 000人次通过系统观看了直播,最高在线人数达到了15 239人,充分验证了系统的性能.     

基于流媒体相关的视频安全组播协议(MSMP)研究

随着无线网络的快速发展和Internet中流媒体视频的巨大成功,无线网络中的视频服务有望在不久的将来得到大规模部署,无线网络上的实时流媒体传输技术已成为研究热点,而其中视频安全组播协议是一个关键问题。但是,由于无线网络中有限的带宽和有限的存储空间,外部的攻击与自适应机制带来的安全性问题在无线流媒体视频中是不可避免的。一个精心设计的密钥管理算法不仅可以明显地提高流媒体视频的性能,还能够保证可靠的数据嵌入以及实时视频应用提供安全支持。如何设计一个高效的密钥管理算法,是当前流媒体视频应用中一个备受关注的问题。针对无线视频应用,针对一个处于开放和不安全的网络环境中的自适应视频应用的密钥管理算法进行了研究,并进行了算法评价。