视频与音频实时多点传输的研究与实现

在开发桌面视频会议系统（GdDCS）的过程中,利用Windows Socket规范实现了视频、音频在网络上的实时多点播送。首先描述了GdDCS系统多点播送的模型,然后讨论视频、音频实时多点传输的实现。     

一种克服磁盘存取受限的视频点播机制

1 引言在视频服务器中,大量的待点播视频流数据以分级存储模式被加以组织,其中点播概率小的节目被存放在低速廉价的光盘库中作为非在线视频(off-line)。为保证视频的播送质量,非在线视频必须先存放到硬盘缓冲区中才能被播放。进一步考虑到网络传输性能因素,将视频服务器按层次化结构进行组织,将待点播的视频数据靠近用户存放,保证缓存的数据     

统一KTV曲库 政府介入过犹不及

为了解决唱片业和卡拉OK经营者的版权纠纷，主管部门在三个城市试点启动了“全国卡拉OK内容管理服务系统”。加入该系统的KTV为顾客播送的歌曲只能通过曲库点播；同时，系统可记录歌曲点播的具体次数，并以此作为歌曲著作权人的酬金依据。且不论这套系统选歌机制是否公平、点播价格是否合理、谁来收费、如何收费等争议因素，单就这种政府部门亲自介入的思路而言，非但不能解决现有的矛盾，反而可能引发新的纷争。     

远程教学中COD的组播实现

本文提出了一种集中式管理、点播服务器分布式放置的远程教学课件点播(Courseware On Demand-COD)系统。在这一体系结构下．采用了新的批处理信道调度策略，对用户实施多播流和补丁流相结合的组播服务。提高了网络带宽利用率，增加了可服务的点播并发流数，同时降低了课件播放延迟时间。     

P2P异步传输点播系统设计与仿真

互联网上大规模Peer-to-Peer(P2P)点播服务存在高效资源调度和不可预知用户行为等挑战.借鉴BitTor-rent(BT)算法原理,提出基于异步传输的P2P点播系统.该系统采用集中式节点定位以及非结构化拓扑,通过异步传榆机制提升文件资源共享度和利用率,并引入视频数据块的优先级和稀有程度改进系统播放连续度.数据包及仿真实验表明本系统在播放连续度、启动时延以及服务器压力等性能指标上的良好性能,充分验证了点播系统中异步传榆机制的可行性.     

流媒体视频点播系统客户端功能的研究与设计

视频点播系统的客户端功能管理对流媒体视频点播系统的性能有重要的影响。本文通过对客户端功能的设计,给出一种适应流媒体点播系统的缓存管理策略和缓存替换算法。结果表明系统资源利用率和节目的播放质量和流畅性都得到了提高,证实了算法在流媒体点播系统中的可行性和有效性。     

应用网络编码的P2P流媒体技术研究进展

P2P流媒体是一种极具潜力的流媒体内容分发技术。在P2P流媒体系统中采用网络编码,有利于进一步提升系统整体性能。针对目前流行的基于数据驱动覆盖网络的P2P流媒体系统框架,根据直播和点播这两种流媒体播送模式,深入讨论和分析了具有代表性的网络编码P2P流媒体技术方案的实现机制及其优缺点。最后,对该方向的研究趋势进行了展望。     

基于集群的VOD系统的动态负载平衡模型

基于多服务器集群的VOD系统能以低成本高性能满足日益增长点播需求,服务器调度和动态负载平衡是实现的关键。本文从校园网VOD用户点播行为特点出发,引入动态负载平衡模型(LBM,Load Balancing Model),清晰地表达了各因素逻辑关系。实验主要对独立性强、任务执行时间不确定的任务,在Linux集群环境下,实现了动态负载平衡模型。实验表明该策略可取得较高负载平衡效率。     

一种分布式VOD系统的方案设计

视频点播(VOD)是目前广受网络用户欢迎的应用服务,而节目调度问题始终是VOD系统方案设计和实现中的一个重要问题。该文针对互联网的用户点播特点,从用户行为和节目流行度入手,详尽分析了系统体系和用户点播流程。通过改进基于流行度的节目调度策略,采用每个节目不同片段分块备份存储和不同时间实时调度相结合的方案。实验表明,该方案的边缘Server资源利用率较高,系统能达到较好的服务性能。     

一种用于大规模P2P点播系统的拓扑结构

提出了一种基于动态时间坐标的分层DHT拓扑结构,解决了因大规模P2P点播系统要求细粒度追踪而难以应用DHT的问题。在动态时间坐标系中,节点的播放点坐标不再随着节点的播放而移动,从而使得DHT能够用于追踪点播系统节点缓存位置。仿真结果证明了方法的有效性。     

基于效用的EPON VoD QoS组播实现机制研究

服务质量无法保证和低效益是IP网络上开展VoD业务面临的主要问题.基于组播业务的网络优先级、用户群的SLA优先级和经济优先级,提出了一个基于效用的EPON VoD组播QoS优先级(效用优先级)算法.在网络拥塞的时候,基于该效用优先级来动态调整组播组的资源分配,不但节省了带宽需求和降低包丢失率,而且可通过将网络资源汇聚到高价值的业务上,提高带宽的效益.通过对变长和无序EPON Ethernet下行帧进行基于效用的定长和有序的改进,可减少VoD业务流的包时延抖动.仿真实验结果很好地验证了该机制的优点.     

DPVoD:基于P2P的视频点播体系结构

可扩展性和可靠性是视频点播系统大规模应用的关键,提出了一种P2P点播系统结构DPVoD.系统基于应用层组播,用户以订制的缓存为其他节点提供服务,并形成相对独立的共享并发流组播树,组播树之问根据拥有的视频数据的重合程度而建立不同的组邻居关系,以此为基础,采用多种机制来提高系统性能:组协同工作、父亲点选择策略、状态控制协议和失效恢复等.定义并分析了可能对系统性能有严重影响的结尾雪崩问题并提出解决方案.对系统基本性能进行了理论分析.仿真结果表明,在静态和动态环境中,DPVoD系统的并发流占用数和利用率、可靠性等性能均优于类似系统.     

A novel dynamic pricing scheme for contributing peers in the VoD system

In this paper we have proposed a dynamic pricing scheme for the contributing peers in the Video on Demand (VoD) system. The scheme provides an effective mechanism to maximize the profit through the residual resources of the contributing peers. A utilization function is executed for each contributing peer to estimate the utility factor based on the parameters such as initial setup cost, holding cost, chaining cost and salvage cost. In this paper, we urge an effective dynamic pricing algorithm that efficiently utilizes a range of parameters with a varying degree of complexity. The key findings of the algorithm are (i) each contributing peers are benefitted by the monetary based on its resource contributions to the VoD system and (ii) a high degree of social optimum is established by proficiently aggregating the contributing peer’s resources with the overall resources of the VoD system. We validate our claim by simulating the proposed dynamic pricing scheme with other standard pricing schemes such as altruism, cost model and game theory perspective. The result of our dynamic pricing scheme shows the best utility factor than other standard pricing schemes.     

结合IP组播的P2P流媒体直播系统

在流媒体系统中利用P2P技术与IP组播各自的优势,提出了一种结合IP组播的P2P流媒体直播系统,不仅能够充分利用用户节点的资源,减轻流媒体服务器与骨干网的负载,提高系统的可扩展性和可用性,而且有效地提高了P2P流媒体直播系统中视频流的服务质量。     

数字化校园中高清流媒体VoD系统的架构

流媒体视频点播系统已经成为下一步网络应用的重要发展方向。结合校园网络结构特点,针对VoD系统中的重要瓶颈问题,分析了VoD服务系统架构,论证了系统架构中应采用的IP组播技术,并对视频片源的转制和实验结果进行了讨论。     

On a unified architecture for video-on-demand services

Current video-on-demand (VoD)) systems can be classified into two categories: 1) true-Voll) (TVoD) and 2) near-VoD (NVod)). TVoD systems allocate a dedicated channel for every user to achieve short response times so that the user can select what video to play, when to play it, and perform interactive VCR-like controls at will. By contrast, NVoD systems transmit videos repeatedly over multiple broadcast or multicast channels to enable multiple users to share a single video channel so that system cost can be substantially reduced. The tradeoffs are limited video selections, fixed playback schedule, and limited or no interactive control. TVoD systems can be considered as one extreme where service quality is maximized, while NVoD systems can be considered as the other extreme where system cost is minimized. This paper proposes a novel architecture called Unified VoD) (UVoD) that can be configured to achieve cost-performance tradeoff anywhere between the two extremes (i.e., TVoD and NVoD). Assuming that a video client can concurrently receive two video channels and has local buffers for caching a portion of the video data, the proposed UVoD architecture can achieve significant performance gains (e.g., 400% more capacity for a 500-channel system) over TVoD under the same latency constraint. This paper presents the UVoD architecture, establishes a performance model, and analyzes UVoD's performance via numerical and simulation results     

An active buffer management technique for providing interactive functions in broadcast video-on-demand systems

Multicast delivery is an efficient approach to the provision of a video-on-demand (VoD) service. Interacting with the video stream is a desirable feature for users. However, it is a challenging task to provide the functionality in the multicast environment because a lot of users share multicast delivery channels. In this paper, we propose an active buffer management technique to provide interactive functions in broadcast VoD systems. In our scheme, the client can selectively prefetch segments from broadcast channels based on the observation of the play point in its local buffer. The content of the buffer is adjusted in such a way that the relative position of the play point is kept in the middle part of the buffer. Our simulations show that the active buffer management scheme can implement interactive actions through buffering with a high probability in a wide range of user interaction levels.     

IP组播技术及其在VoD系统中的应用

介绍了IP组播技术，为支持二层组播实现了IGMP SNOOP协议，并在此基础上设计和实现了基于IP组播技术的VoD系统。     

基于可扩展视频服务器集群的视频点播系统设计

随着计算机技术和高速网络技术的发展,视频点播系统已变成现实,并且具有巨大的潜在需求。利用视频对象简介能够给用户一个友好的互动收视环境。可扩展视频服务器集群可以适应未来的用户需求的快速增长。视频对象分段技术和前缀缓存技术使视频文件按照一定的缓存策略以分段方式分布在协作式的缓存服务器集群中,以利于服务器集群的负载平衡和减少对用户的启动延迟。系统还引入了IP组播技术来减少对网络带宽的开销。该文提出了混合式的协作缓存和IP组播的方式交付视频对象,并描述了它是如何工作的。     

DVB-IPTV content download services—overview and use cases

IPTV services have been widely deployed by network operators around the world over the last years. However, real-time streaming of Linear TV and Video-on-Demand (VoD) offerings, especially in High Definition quality, still puts a high burden on the network and content servers concerning bandwidth, Quality-of-Service, processing performance and scalability if 100.000s of users have to be supported simultaneously. While multicast delivery can cope with some of these problems for Linear TV services, the unicast VoD services cannot take advantage of that and especially the request for on-demand content is expected to substantially grow in the future. With the introduction of Content Download Services (CDSs), operators have the option to provide IPTV services in innovative ways: They can provide high-quality video services to users with limited access bandwidth, offload the streaming request for blockbuster movies at peak times from the VoD servers or provided personalized advertisements for insertion into a live program event in advance to the users end device. The Digital Video Broadcast (DVB) Project has recently finalized its CDS specification within its IPTV specification efforts. DVB CDS supports push and pull delivery models with unicast, multicast and peer-to-peer distribution in order to enable various business models and use cases. In this work we introduce the specified technology and map it to example use cases and business models.