HLS直播流媒体传输系统的冗余优化

对HTTP Live Streaming深入研究之后,发现该协议在直播流媒体传输过程中存在视频流索引文件重复传送的问题。详细阐述了服务器与客户端之间的交互过程,并通过对网络监控软件的使用,检测到交互过程中服务器传输给客户端的视频流索引文件存在较大的冗余,造成网络带宽开销增大。提出一种可行的改进方案,在.m3u8文件中添加一个#EXT-X-MEDIA-SEQUENCE-LAST标签,并使服务器和客户端都对该标签进行识别。通过对网络占用率的对比分析,改进后的方案对网络带宽的占用率明显减小,进而验证了该改进方案的可行性。     

基于代理的分布式视频流点播传输策略

视频流传输具有带宽高、周期长的特点,使网络带宽成为了制约视频流点播应用发展的主要因素.本文针对现有网络技术条件,充分利用客户端I/O带宽、本地缓存及网络带宽资源,设计了一个适用于大规模点播应用的基于代理的分布式视频点播传输策略.该策略中各本地网络设有一视频流代理服务器用于保存部分视频的部分内容,并按动态批处理的方式来接纳并服务请求用户.视频传输时,服务器与代理端之间采用单播传输机制,在代理与客户端之间采用单播与多播相结合的方式.实验表明该策略可以大大减少对骨干网络带宽的需求,并能为客户端提供理论上的零启动延时服务.     

媒资交互平台服务质量控制体系设计

结合辽宁广播电视台媒体资产管理与交互平台设计及运行情况,从应用环境、网络环境、网络带宽需求等方面分析了媒资交互平台在设计和使用过程中面临的问题.在系统设计时,采用服务质量控制体系设计的思路,为媒体资产管理与交互平台提供更好的服务能力.着重介绍了媒资交互平台服务质量控制体系设计的各种策略,包括流程优先级的设置、EMB传输服务器的任务分配、文件共享服务器负载分配,并重点阐述了使用服务器灵活指定技术实现对文件的转码控制.     

基于嵌入式技术和GPRS通信的图像传输系统设计

本文提出了一种无线远程图像传输的解决方案。在本方案中,通过GPRS网络进行PPP协议拨号上网,在嵌入式端运行Boa服务器,Boa服务器通过CGI程序生成动态网页并与客户端进行交互,服务器将从具有OV511芯片的USB摄像头采集图像,并采用JPEG格式进行压缩后通过动态网页链接,使得客户端可以直接获得服务器端的图像数据。经实验测试,系统能够对远程监控图像实现高质量、实时地传输。     

基于RTP的网络视频传输的应用研究

随着移动通信网络的发展,对于网络视频传输的要求越来越高。文中着重研究了RTP／RTCP（实时传输协议／实时传输控制协议）,提出了一种基于网络实时传输的视频监控系统的设计方案。介绍了视频服务器模块的设计,阐述了利用TCP（传输控制协议）实现服务器与客户端的交互通信,以及利用RTP／RTCP实现基于H．264压缩格式视频流的传输。     

无线Mesh网络视频监控系统客户端软件设计

结合无线Mesh网络(WMN)技术的特性,提出了一种基于Mesh网络的视频监控系统应用方案。利用DirectShow技术开发了基于WMN的视频监控系统客户端软件,软件采用客户机/服务器模式,实现了视频流的网络传输及远程控制等功能。终端通过摄像机和视频服务器完成视频采集压缩,利用WMN平台进行传输,客户端在Mesh网络的覆盖范围内通过因特网进行视频数据接收,实现无线视频监控。测试结果表明,系统播放流畅、实时性强,在无线视频监控中具有广泛的应用前景。     

基于智能终端的流媒体视频播放平台

分析研究了基于智能终端流媒体内容的分配机制、传输协议.针对智能终端,对流媒体视频播放平台的原理和设计进行了研究综述.开发了一个具有后台管理功能的流媒体视频播放平台.采用基于开源代码的VLC媒体软件和Live555流媒体服务器作为网络流媒体服务器对视频流进行网络传输与分发.采用FFmpeg音视频流方案对媒体文件进行转码封装及流化处理,处理后的媒体文件能够在以智能终端为客户端的平台上播放.     

MPEG-1的RTP应用

提出了一种把RTP应用于MPEG-1的方案,该方案把MPEG-1文件分解成音频流和视频流,并按RTP的相应规则打包传输;设计了一种MPEG-1的索引,根据索引可以快速的对MPEG-1文件进行解析;并对应MPEG-1的特点提出相应的错误恢复策略.     

基于ARM11的视频监控系统设计

为了实现远程视频监控的功能,提出了一种基于ARM 11和嵌入式Linux的远程视频服务器的方案.使用V4L2接口对数据进行采集,选择了具有很高压缩效率的H.264压缩标准,通过CPU内部集成的MFC模块实现对视频流的硬件压缩,在移植到系统的boa服务器上编写了CGI脚本响应远程客户端的响应.在客户端中,通过SDL和FFmpeg库提供的API接口完成了对经过网络传输到客户端上的视频数据的解码与播放,完成了包括视频的采集、编码、传输、显示各个功能模块的整个系统设计.     

基于IIS平滑流式处理的移动流媒体系统

针对当前流媒体传输协议在无线网络中的不足,采用IIS平滑流式处理技术设计了基于服务器/客户端模式的移动流媒体系统。详细讨地论了微软的IIS平滑流式处理协议,采用该协议传输音/视频数据,搭建了基于IIS7 Web服务器的流媒体服务,设计了一款基于Windows Phone 7智能手机的流媒体播放器客户端。通过在WiFi网络环境下测试该系统,在直播和点播两种播放模式下,客户端播放的视频画面清晰流畅。通过仿真无线网络带宽的变化,验证了IIS平滑流式处理根据客户端的可用带宽实时调整传送到客户端视频流的质量的特性。     

Scalable On-Demand Streaming of Nonlinear Media

A conventional video file contains a single temporally-ordered sequence of video frames. Clients requesting on-demand streaming of such a file receive (all or intervals of) the same content. For popular files that receive many requests during a file playback time, scalable streaming protocols based on multicast or broadcast have been devised. Such protocols require server and network bandwidth that grow much slower than linearly with the file request rate. This paper considers ldquononlinearrdquo video content in which there are parallel sequences of frames. Clients dynamically select which branch of the video they wish to follow, sufficiently ahead of each branch point so as to allow the video to be delivered without jitter. An example might be ldquochoose-your-own-endingrdquo movies. With traditional scalable delivery architectures such as movie theaters or TV broadcasting, such personalization of the delivered video content is very difficult or impossible. It becomes feasible, in principle at least, when the video is streamed to individual clients over a network. For on-demand streaming of nonlinear media, this paper analyzes the minimal server bandwidth requirements, and proposes and evaluates practical scalable delivery protocols.     

Network Bandwidth Requirements for Scalable On-Demand Streaming

Previously proposed streaming protocols using broadcast or multicast are able to deliver multimedia files on-demand with required server bandwidth that grows much slower than linearly with request rate, or with the inverse of client start-up delay. The same efficiencies can be achieved for network bandwidth if delivery is over a true broadcast channel. This paper considers the required network bandwidth for on-demand streaming over multicast delivery trees. We consider both simple canonical delivery trees, and more complex cases in which delivery trees are constructed using both existing and new algorithms for randomly generated network topologies and client site locations. Results in this paper quantify the potential savings from use of multicast trees that are configured to minimize network bandwidth rather than the latency to the content server. Further, we determine the network bandwidth usage of particular immediate service and periodic broadcast on-demand streaming protocols. The periodic broadcast protocol is able to simultaneously achieve close to the minimum possible network and server bandwidth usage.     

Cable-TV-based home video streaming system: practice and experience

This article presents a practical home video streaming system that has actually been implemented and deployed for commercial services on a cable television network. Because streaming components and network connections of a cable TV network are considerably different from those of desktop streaming systems available on the Internet, traditional systems and techniques for video streaming are not enough for a cable TV network. Therefore, several special systems and server-centric streaming techniques have been developed for a cable TV network and home video clients. In particular, server-centric streaming techniques are crucial because a set-top box, which is the client in the case of a home video streaming system, lacks processing power. We have developed a highly efficient streaming server using network acceleration and data bypassing techniques. As a result, our stateof- the-art streaming server enables high scalability and provides various content navigation modes, including faster playback, to off-the-shelf set-top boxes.     

应用于P2P网络串流的实时监控系统

点对点(Peer-to-Peer,P2P)传输架构的新技术能利用用户的网络带宽以及运算能力来分担串流服务系统的负担,对于该网络进行实时监控已经成为近年来的一个研究热点.分析了应用于P2P网络串流的实时监控系统,指出跟踪监控的3类主要方法,即网络级别、被动的应用程序级别和主动应用程序级别的监控.给出了主动应用程序级别的监控模式下监控系统的架构与组成,并通过实验分析了其监控性能.     

基于嵌入式流媒体服务器的视频点播系统

移动通信网络流媒体服务资费较高,限制了人们在没有有线电视、宽带互联网连接、无线WiFi互联网连接的地方用手机收看视音频节目.针对这一现状,提出了一种基于嵌入式流媒体服务器的多功能视频点播系统.以ARM板和WiFi网络适配器作为流媒体服务器,设计一款Android手机播放器作为客户端,实现在智能手机上、多个客户端同时免流量接收服务器本地或外接设备推送的高清、超高清视频.该系统适用于公交、广场、电梯、商场、景区等场合,人们用手机观看视音频,实现不用耗费自己的流量,自由快速地选择自己喜欢的节目.     

QoE optimization for HTTP adaptive streaming: Performance evaluation of MEC-assisted and client-based methods

Seamless streaming of high quality video under unstable network condition is a big challenge. HTTP adaptive streaming (HAS) provides a solution that adapts the video quality according to the network conditions. Traditionally, HAS algorithm runs at the client side while the clients are unaware of bottlenecks in the radio channel and competing clients. The traditional adaptation strategies do not explicitly coordinate between the clients, servers, and cellular networks. The lack of coordination has been shown to lead to suboptimal user experience. As a response, multi-access edge computing (MEC)-assisted adaptation techniques emerged to take advantage of computing and content storage capabilities in mobile networks. In this study, we investigate the performance of both MEC-assisted and client-side adaptation methods in a multi-client cellular environment. Evaluation and comparison are performed in terms of not only the video rate and dynamics of the playback buffer but also the fairness and bandwidth utilization. We conduct extensive experiments to evaluate the algorithms under varying client, server, dataset, and network settings. Results demonstrate that the MEC-assisted algorithms improve fairness and bandwidth utilization compared to the client-based algorithms for most settings. They also reveal that the buffer-based algorithms achieve significant quality of experience; however, these algorithms perform poorly compared with throughput-based algorithms in protecting the playback buffer under rapidly varying bandwidth fluctuations. In addition, we observe that the preparation of the representation sets affects the performance of the algorithms, as does the playback buffer size and segment duration. Finally, we provide suggestions based on the behaviors of the algorithms in a multi-client environment.     

基于ZigBee技术的智能家居系统

通常把智能家居定义为利用计算机、网络和自动化控制技术,通过一个固定的平台将与家居生活有关的设备集成到一个系统中。系统通过无线通信技术进行各个节点和平台之间的通信,类似于一个家庭的局域网。文中设计了一种基于ZigBee技术的智能家居系统,除了能够利用ZigBee无线通信技术对室内的温湿度信息的实时感知,开关控制外,本系统还设计了视频流服务器,能够将室内的视频信息通过网络传输到远程客户端,如手机或者PC Web客户端。另外,此视频流服务器具有较强的扩展功能,能够进行各种常用协议的传输以及支持各种常见视频设备的数据采集。     

Transcoding media for bandwidth constrained mobile devices

Bandwidth is an important consideration when dealing with streaming media. More bandwidth is required for complex data such as video as opposed to a simple audio file. When delivering streaming media, sufficient bandwidth is required to achieve an acceptable level of performance. If the information streamed exceeds the bandwidth capacity of the client the result will be ‘choppy’ and incomplete with possible loss of transmission. Transcoding typically refers to the adaptation of streaming content. Typical transcoding scenarios exploit content‐negotiation to negotiate between different formats in order to obtain the most optimal combination of requested quality and available resources. It is possible to transcode media to a lesser quality or size upon encountering adverse bandwidth conditions. This can be accomplished without the need to encode multiple versions of the same file at differing quality levels. This study investigates the capability of transcoding for coping with restrictions in client devices. In addition, the properties of transcoded media files are examined and evaluated to determine their applicability for streaming in relation to a range of broad device types capable of receiving streaming media. Copyright © 2005 John Wiley & Sons, Ltd.