流媒体的拥塞控制技术研究综述

作为多媒体和网络领域得交叉学科，流媒体技术的应用和研究得到了迅速发展，但由于流媒体与传统网络媒体有着显著的差别．对流媒体的研究也就面临着巨大的挑战。其中网络拥塞是影响视频通信质量的一个重要因素，该文总结了视频传输的各种拥塞控制策略，并对现有的拥塞控制协议进行了比较，对提高视频传输的质量有一定的意义。     

基于累积时延的流媒体传输模糊拥塞控制

为保证网络流媒体传输质量,在流媒体的传输中需要采用有效的拥塞控制策略.结合流媒体数据对时延敏感的特点,提出了一种基于累积时延的模糊拥塞控制算法,该算法在流媒体数据流传输过程中检测和跟踪其时延,在转发分组数据前,根据容忍时延阈值,丢弃超时数据包,减少不必要的带宽浪费,并且对所到达的数据流按照累积时延进行优先级分类,把全局性缓冲区和各队列的局部性缓冲区按照正常、拥塞避免和拥塞的规则划分为3个具有交叉过渡域的阶段,然后采用整体和局部相结合的拥塞控制方法,实现队列调度过程中的模糊处理,从而对网络拥塞进行有效的控制.理论分析和实验结果表明,使用基于累积时延的模糊拥塞控制算法,能有效改善流媒体的传输性能,是解决流媒体传输拥塞控制的有效途径,并能对提高网络性能起到重要作用.     

数据报拥塞控制协议（DCCP）研究

1.引言众所周知,网络的视频/音频服务在飞速发展中,但是流媒体的质量却不高。应用的开发者们想尽办法来提供尽可能平稳的流媒体服务,他们的解决方案大部分基于TCP和UDP协议。TCP协议可以提供可靠的端到端的传输控制,但是它的传输速率抖动大,而流媒体并不需要完全可靠的传输;UDP协议简单实用,但是不提供拥塞控制,不能和TCP友好共存,容易引起网络的拥塞。研究者们在分析了问题和比较了     

面向TCP的流媒体传输编码码率自适应算法

由于网络的时变性和异构性,以及在拥塞情况下的高丢包率,利用TCP传输流媒体数据是Internet流媒体分发系统提高流媒体分发质量的首选方案。由于TCP具有超时或错误重传机制,在网络拥塞情况下,难以保证高码率流媒体数据传输的实时性,因此提出一种面向TCP流媒体传输的编码码率自适应算法(TCP_RA)。该算法根据流媒体发送应用层缓冲区读写指针差值调整流媒体发送端的编码码率适应网络带宽的变化。仿真实验对比分析了该算法与基于UDP之上TFRC协议的流媒体传输码率自适应算法在流媒体传输质量上的差别。结果表明,该算法在网络环境较差的情况下有效地提高了流媒体传输质量。并且该算法容易实现,值得推广。     

利用运动强度自适应传输视频内容

在异构的网络环境下,如何自适应地传输满足多种终端设备和不同用户需求的视频内容具有重要的意义.以达尔文流媒体服务器为实验平台,提出一套基于运动强度的视频自适应传输策略.在服务器端通过检测丢包率来控制发送速率等级,避免网络拥塞,并采取一定策略消除因丢帧而产生的马赛克;在自适应策略中加入了运动强度信息,针对不同的运动强度级别进行不同的处理,使得综合视频质量得到提高.实验结果表明,文中的自适应策略不仅可以避免网络拥塞,而且可以改善视频播放质量.     

视频通信的网络自适应传输控制技术

针对视频传输中的拥塞控制问题，对网络自适应传输控制技术进行了研究，该技术综合了UDP与TCP的传输特性，能够对网络拥塞进行自适应控制。提出了该技术的技术框架和实现方案，并将其应用在一个端到端的视频传输系统中。实验结果表明，网络自适应传输控制技术可以为视频通信提供良好的传输质量保障。     

Internet视频传输的拥塞控制策略

网络拥塞是影响Internet视频通信质量的一个重要因素。该文分析了单播和组播中视频传输的各种拥塞控制策略，并对各种拥塞控制策略的带宽利用率和服务灵活性进行了比较，对提高Internet视频传输的质量有一定的意义。     

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P2P覆盖网的流媒体高质量传输策略

目前，在Internet上传输流媒体还存在许多困难，因为大量的媒体文件传输要求较高的带宽，所以在网络环境无法满足的情况下，容易造成丢包和延迟现象，降低流媒体的传输质量。该文提出了一个流媒体高质量传输策略，从质量控制的差错控制与拥塞控制两方面来降低丢包率，保证可靠的流媒体传输。     

视频流媒体传输失真研究

由于网络传输引起的视频流媒体质量损失（称为传输失真）是流媒体QoS中最重要的参考指标，通常只能在终端系统解码后获得．本文根据视频流媒体编解码、错误隐藏、错误扩散等理论进行分析，提出了一个视频流媒体传输失真模型，谊模型可以在发送端通过网络传输质量和视频流媒体特性参数估算视频流媒体的最终表现质量，可以为流媒体同步、控制算法提供定量的参考指标．该模型针对常见的视频流媒体处理机制进行建模，并不局限于特定的编解码格式，具有更广泛的实用价值．     

一种基于TCPW的流媒体端到端拥塞控制方法

由于网络的时变性和异构性,流媒体系统往往不能很好地适应网络带宽的变化。为此,结合Darwin streaming server(DSS)的源代码对其拥塞控制方法进行分析,同时运用TCP Westwood(TCPW)的带宽估计算法来改进DSS的拥塞控制策略,并搭建了实际的视频流传输系统对该策略进行验证。实验结果表明,改进后的拥塞控制策略不仅能有效地提高接收端的视频质量,而且带宽利用率也有明显的提高。     

Evalvid-RA: trace driven simulation of rate adaptive MPEG-4 VBR video

Due to the increasing deployment of conversational real-time applications like VoIP and videoconferencing, the Internet is today facing new challenges. Low end-to-end delay is a vital QoS requirement for these applications, and the best effort Internet architecture does not support this natively. The delay and packet loss statistics are directly coupled to the aggregated traffic characteristics when link utilization is close to saturation. In order to investigate the behavior and quality of such applications under heavy network load, it is therefore necessary to create genuine traffic patterns. Trace files of real compressed video and audio are text files containing the number of bytes per video and audio frame. These can serve as material to construct mathematical traffic models. They can also serve as traffic generators in network simulators since they determine the packet sizes and their time schedule. However, to inspect perceived quality, the compressed binary content is needed to ensure decoding of received media. The EvalVid streaming video tool-set enables this using a sophisticated reassembly engine. Nevertheless, there has been a lack of research solutions for rate adaptive media content. The Internet community fears a congestion collapse if the usage of non-adaptive media content continues to grow. This paper presents a solution named Evalvid-RA for the simulation of true rate adaptive video. The solution generates real rate adaptive MPEG-4 streaming traffic, using the quantizer scale for adjusting the sending rate. A feedback based VBR rate controller is used at simulation time, supporting TFRC and a proprietary congestion control system named P-AQM. Example ns-2 simulations of TFRC and P-AQM demonstrate Evalvid-RA’s capabilities in performing close-to-true rate adaptive codec operation with low complexity to enable the simulation of large networks with many adaptive media sources on a single computer.     

基于TCP端口的拥塞控制算法研究

随着计算机网络的快速发展,人们对网络资源的要求也越来越高,尤其是近年来如语音,图像等多媒体流在网络上大量涌现,网络拥塞问题也随之变得严重,而网络拥塞也一直是计算机网络研究的重点和热点问题之一。该文将阐述目前基于TCP/IP协议的几种典型拥塞控制算法,并指出其优缺点,同时给出两种拥塞控制方法的比较。     

A Control-Theoretic Approach to Rate Control for Streaming Videos

As streaming videos are becoming increasingly popular, it is important to understand the end-to-end streaming system and to develop effective algorithms for quality control. In this paper, we address the problem of rate control for streaming videos with a control-theoretic approach. Among the various control knobs, video bit rate is one of the most effective in the sense that it has a direct impact on the interaction between the video coder and network system. While increasing rate reduces the coder-induced distortion, it may also cause congestion at a bottleneck link. The packet loss due to congestion will, then, increase the distortion of the decoded video. We model end-to-end video steaming as a feedback control system, taking into account video codec and sequence characteristics, rate control, active queue management, and receiver feedback. We then develop effective proportional (P) controllers to stabilize the received video quality as well as the bottleneck link queue, for both homogeneous and heterogeneous video systems. Simulation results are presented to demonstrate the efficacy of the P controllers and the viability of the proposed control-theoretic approach.     

A new fast friendly window-based congestion control for real-time streaming media transmission

1 Introduction In the current Internet, not all applications use TCP and they do not follow the same concept of fairly sharing the available bandwidth. The rapid growing of real-time streaming media applications will bring much UDP traffic without integrating TCP compatible congestion control mechanism into Internet. It threats the quality of service (QoS) of real-time applications and the stability of the current Internet. For this reason, it is desirable to define appropriate rate rule…     

TCP友好拥塞控制研究

因使用的传输协议缺乏有效的拥塞控制机制,造成流媒体传输数据包时会有大的延迟和丢失,导致流媒体播放不清晰、不同步、播放停顿等质量问题.针对流媒体传输而提出的TCP友好拥塞控制是当前网络协议研究的一个热点.比较分析了当前较有影响的TCP友好拥塞控制机制,并给出今后的研究方向.     

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。     

A P2P streaming architecture supporting scalable media

Peer-to-peer (P2P) streaming solutions are changing the way real-time multimedia transmission is distributed over the Internet. The advances in video coding, like Scalable Video Coding, also turns possible high-quality/definition video distribution and consumption. The recent push in using the standard HTTP protocol for streaming videos in the World Wide Web, is also making converged entertainment services come closer to global deployment across TV, Tablet and mobile devices. The combination of Scalable Video, P2P networks and Web technologies for transmitting high-quality live and time-shifted media contents, is a potential area of innovation and a very actual research topic. This paper describes the architecture of a quality-centric P2P distribution network supporting adaptive and scalable streamable media, that decouples the transport mechanisms from the media content type and structure (video, audio, timed-data, timed-text), irrespective of their encoding schemes. The set of P2P streaming protocols designed for the network enables streaming of live and on-demand media, with very low signaling cost. Prototypes of the P2P network components were implemented and integrated in the streaming platform of EU FP7 SARACEN Project. A suite of tests for evaluation of the performance of the solution demonstrates that it keeps a fairly stable quality level with reduced amplitude and frequency of variations, raising the overall quality perceived by the end-user.     

流媒体自适应传输控制的研究

流媒体是指多媒体数据流在网络上一边传输一边播放的一种多媒体通信服务.提供尽力而为服务的Internet不能为流媒体保证网络带宽、传输延迟、分组丢失以及分组错误等,而自适应传输控制机制能够提高流媒体服务的传输服务质量和传输服务的公平性.本文探讨流媒体自适应传输控制技术所涉及的各个方面,包括拥塞控制、质量自适应和错误控制.