因特网上视频多点传输算法研究

本文研究因特网上进行视频多点传输的问题.在分析了资源预约协议和智体反馈控制机制的基础上,基于分层编码技术提出一种新的视频传输算法.文中利用ns-2网络模拟器进行了性能评价,结果表明该算法在保证视频基本服务质量的条件下,具有较好的公平性和可扩放性.     

End-to-End QoS for Video Delivery Over Wireless Internet

Providing end-to-end quality of service (QoS) support is essential for video delivery over the next-generation wireless Internet. We address several key elements in the end-to-end QoS support, including scalable video representation, network-aware end system, and network QoS provisioning. There are generally two approaches in QoS support: the network-centric and the end-system centric solutions. The fundamental problem in a network-centric solution is how to map QoS criterion at different layers respectively, and optimize total quality across these layers. We first present the general framework of a cross-layer network-centric solution, and then describe the recent advances in network modeling, QoS mapping, and QoS adaptation. The key targets in end-system centric approach are network adaptation and media adaptation. We present a general framework of the end-system centric solution and investigate the recent developments. Specifically, for network adaptation, we review the available bandwidth estimation and efficient video transport protocol; for media adaptation , we describe the advances in error control, power control, and corresponding bit allocation. Finally, we highlight several advanced research directions.     

利用IP Multicast技术实现Internet网上视频通信

目前,多播通信技术逐渐成为互联网上发展的一个重点,如何利用多播通信技术实现在互联网上的视频点播业务更是被业内人士所关注。把传统电视节目、视频传输、频道点播搬上互联网成为广电系统研究的方向。本文从IP多播技术的基本概念出发,对IP多播技术做一比较全面的介绍,通过IP QoS服务机制对IP多播视频流在网络传输中加以控制,达到利用IP多播技术在互联网上实现视频通信（视频点播）的目的。     

Explicit Multicast Extension (Xcast+) for Efficient Multicast Packet Delivery

In this letter, we propose a new multicast scheme, named Xcast+, which is an extension of Explicit Multicast (Xcast) for an efficient delivery of multicast packets. The mechanism incorporates the host group model and a new control plane into existing Xcast, and not only does it provide the transparency of traditional multicast schemes to senders and receivers, but it also enhances the routing efficiency in networks. Since intermediate routers do not have to maintain any multicast states, it results in a more efficient and scalable mechanism to deliver multicast packets. Our simulation results show distinct performance improvements of our approach compared to Xcast, particularly as the number of receivers in a subnet increases.     

数字视频广播中可靠组播的实现

数字视频广播是一种新型的电视广播技术,它和计算机技术相融合,利用现有的有线电视网络实现大范围远距离的可靠内容的广播.由于不是所有的主机都需要这些报文,因此IP广播浪费了网络资源,而将IP组播技术用于数字视频广播,能有效地利用网络资源.     

一种基于ADSL接入技术的视频组播方案

~~图3ISM的组播实现DSLAM内置的ISM板,可完成IGMPserver犤4犦的功能,所有的视频流的PVC,通过RFC1483桥接封装,在DSLAM的ADSLLT板上完成复制,这样可以减轻对网络侧的流量压力,从而保证高质量的视频流到每个用户。ISM板的组播实现如图3,其步骤如下:(1)用户发出一IGMP请求,申请加入/离开一视频频道组播组,该请求被直接送到ISM板。(2)ISM板检查其寻址信息的IP组播地址,并与相应的频道的IP地址相比较。(3)通过私有协议,ISM板动态地请求网络终结板(NT)通过LT板为申请用户复制该视频频道数据。(4)LT板动态复制频道数据并传…     

一种缓冲区驱动的自适应视频多播系统

利用基于控制理论的自适应传输机制,提出一种接收方缓冲区驱动的自适应视频多播系统,实现了在不可预约带宽网络环境中的视频自适应传输.仿真结果验证了方法的有效性,可适用于不同的拥塞控制算法和编码算法,扩展性良好.     

IP组播技术及其在视音频传输中的应用

主要阐述有关IP组播技术的基本概念、组播树、路由协议等,探讨利用IP组播实现视频传输的条件、QoS、关键技术,并展望了该项技术的前景.     

Scalable Video Multicast Over Multi-Antenna OFDM Systems

We propose a framework for efficient scalable video multicast over downlink orthogonal frequency-division multiplexing (OFDM) systems with multiple transmit antennas. In conventional video multicast systems, the achievable transmission rate is determined by the user with the worst channel condition, and the system saturates the capacity when the number of users increases. To accommodate the heterogeneous channel conditions and device capabilities of various users, scalable video coding (SVC) encodes video streams into base and enhancement layers. We exploit the advances in multi-antenna OFDM and the layered nature of SVC, and propose a framework for scalable video multicast which guarantees the base layer quality for all users while making best use of limited resource for the enhancement layer of users with good channel conditions. We show that the resource allocation that includes the transmit precoding, subcarrier allocation, and bit and power allocation is a very difficult optimization problem. A low-complexity suboptimal algorithm is proposed which is suitable for practical implementations. Simulation results are provided to show the effectiveness of the proposed solution.     

Advances in Wireless Video Delivery

This paper reviews practical video delivery technologies, examining existing mobile networks, commercialized or standardized transport, and coding technologies. Compression efficiency, power dissipation, and error control are intrinsic issues in wireless video delivery. Among these issues, error control technologies are evaluated at four layers: 1) layer-1/2 transport; 2) end-to-end transport layer such as TCP/IP or RTP/UDP/IP; 3) error-resilience tool and network adaptation layer) and 4) source coder layer. Layer-1/2 transport tends to provide two distinct conditions: one quasi-error-free, in which upper layer error control technologies show a limited improvement, and one with a burst of errors during the fading period, in which the adaptability of error control is essential. Emerging mobile network quality of service will have a large variation of bandwidth and delay. Thus, adaptive rate control and error recovery are identified as more crucial issues for future research.     

多播视频流的在线场景检测技术

多播在线处理系统必须满足视频流的实时性要求。介绍了基于MBone网络进行多播传输所需的在线视频场景检测技术。场景变化检测算法是基于直方图之差的。     

IPv6视频组播系统研究与设计

为了解决大数据量的视频数据在网络上传输的拥塞问题,提高网络带宽的利用率,文中基于微软的Directshow 技术,研究和实现了一种IPv6网络协议下的视频组播系统.该系统通过TCP建立服务器与各个客户端之间的连接管理,并利用RTP实时流媒体协议传输视频数据.根据测试结果分析,此设计不仅有效地节约了网络带宽,而且可以保证视频画面的实时性及准确性,具有一定的实用价值.     

多播技术在视频服务的应用研究

本文结合视频服务的几个特点,对三种多播技术Batching、Patching与 Chaining/Tree在视频服务中应用做了分析,并从视频服务器和全局网络资源的利用等角度做了对比,最后讨论了其实现的可能性。     

基于IP组播的船载无线视频监控系统

文章给出了基于IP组播的无线视频监控系统,此系统主要实现对内河船舶船载目标的监控。给出了系统模型,描述了系统的核心模块和组播网络的结构,并介绍了网络组播软件的设计。     

异步应用层多径合成视频群播的带宽分配

主要考虑使用者或对等（peer）进入系统要求服务的先后顺序来构建应用层群播，以支持在对等网络（Peer-to-Peer Network）上进行多媒体串流服务。虽然先前也有类似研究，然而却未能真正考虑在真实网络上每个对等皆拥有不同网络带宽的事实，而本文的研究则是考虑对等的带宽及其带宽分配问题，并提出有效的方法来合成带宽，使得要求服务的对等得以平顺地连续播放影片。为验证所提研究方法的效能，进行一系列在各种环境下的仿真分析，而结果则充分显示所提方法能有效地降低网络带宽的需求以及服务器的负载。     

喷泉码及其在无线视频组播环境中的应用

针对无线组播环境,根据中间节点功能不同的情况,提出了两种喷泉码数据分发调度方案.并针对无线组播用户面临信道质量不同的情况,提出一种混合喷泉编码方案,发送端根据组播用户信道质量的差异选取不同码长的喷泉编码.实验证明,对丢包率高、信道质量差的接收端而言,短码长的喷泉编码方案提高了接收端的译码成功概率.     

Progress of Internet Video Technology

In China, currently there are more than 100 million videos being watched everyday on the Internet. There are three kinds of Internet videos: video sharing, Video on Demand (VoD), and Peer-to-Peer (P2P) streaming media. Video sharing is based on browser/server mode, severing user generated content. VoD is based on client/server mode and needs to be paid for. P2P streaming media is based on P2P mode service for hot content. To address P2P traffic optimization and content regulation, China National Information Technology Standardization Technical Committee sets up P2P working group to make relevant standards.