基于电力载波和流媒体的视频监控服务器的实现

文章首先介绍了电力载波通信、视频数据传输以及RTP/RTCP协议的特点,在此基础上提出了一种以电力载波为传输媒介和采用流媒体技术的视频监控服务器设计方案,该方案首先给出了系统的设计框架,然后从软件开发角度具体阐述流媒体服务器实现流程,最后给出实验结果和分析。实验结果表明,在基于电力载波的视频监控服务器中采用RTP/RTCP协议传输视频数据可有效利用网络带宽和降低丢包率。     

基于Directshow的流媒体视频混合及网络传输系统

本文基于Directshow和Windows Socket技术,建立了一种流媒体视频混合及网络传输系统,实现了两路视频流媒体的混合,给出了混合视频流网络传输的解决方案。即在一台视频流媒体服务器、一台终端和一条低带宽线路的条件下同时传输两路/多路动态视频流,并且可以随时调整叠加视频的位置和Alpha值;具有客户端简单,节约带宽,传输效率高,传输信号准确清晰的优点。     

本地带宽资源管理系统的设计与实现

通过分析传统的尽最大努力(BE)传输网络在传输视频流时存在的服务性能高度依赖于本地可用带宽资源问题,设计并实现了本地带宽资源管理系统.可有效管理本地网络带宽资源,同时为视频流传输提供有保证转发(AF)服务.测试结果表明,该系统能有效保障视频流的服务质量(QoS).     

Bitrate allocation among multiple video streams to maximize profit in content delivery networks

Concomitant with rapid advancements in video streaming technology, concurrence video traffic has increased significantly on communication channels. Conflicts often arise among the various video streams on these communication channels when the available bandwidth is limited because the bitrates and transmission range required often vary. This study proposes a server-side-based rate allocation algorithm for content delivery networks (CDNs). Instead of simply considering bitrate selection from the perspective of network and client conditions, the algorithm combines user experience with video bitrate allocation to maximize viewer engagement. First, the values of users are evaluated and a user value computation method is proposed. Second, we developed a profit maximization bitrate allocation approach (PMBAA) that enables both content providers and CDNs to maximize profits by providing guaranteed video quality. At last, the results of test bed experiments and analyses verify that PMBAA enables high-value clients to obtain more preferable bitrates than the HTTP live streaming algorithm developed by Apple Inc.     

率失真优化的无线多跳网络多路径选择算法

随着无线网络技术的发展,基于无线多跳网的视频通信在智能交通、灾难应急和军事指挥等多个领域得到越来越广泛的应用.但是,如何保证无线视频的传输质量,是亟待解决的一个关键问题.已有多路径视频传输研究忽略了信道变化和路径间干扰.针对该问题,提出一种基于率失真预测的多路径选择优化算法.该算法不仅分析了网络拥塞对传输质量的影响,而...     

无线上行视频流的跨层容错传输方法

如何通过资源受限的移动通信终端提升无线上行视频流的抗误性能是亟待解决的重要问题。通过不同通信层次的联合调度,提出了一种跨层容错传输方案。移动通信终端的网络层代理首先利用容错包调度为视频流的延时约束帧集合提供重要性分类,随后该终端的链路层代理利用无线链路单元的优先级调度实现选择性重传。在调度延时与传输带宽限制下,跨层容错传输能够将突发错误转移到延时约束帧集合的低优先级视频数据中,从而在突发易错传输环境中实现了无线链路单元粒度的渐进式传输和平稳退化。     

基于内容感知的视频流媒体渐进式流传输方式

为有效利用传输网络带宽、平衡播出视频质量与用户等待时间之间的矛盾,提出一种基于内容感知的视频流媒体渐进式流传输方式。在视频内容分析和理解的基础上,根据编码关键参数确定视频序列中各帧的重要性,估计帧内片层数据重要性。采用MGS编码,在MobileIP测试平台上进行实验。实验结果表明了该传输方式的正确性和有效性,能够适应网络带宽和质量可伸缩的视频流媒体。     

视频点播网站的设计与实现

视频点播系统是集通信网络技术、多媒体技术、计算机和数据库技术于一体的崭新的视频服务系统。此系统还运用了智能视频流技术,针对不同的网络带宽和传输速度采取不同的传输方式。     

网络课件中音视频文件与网页内容的同步

介绍了现代远程教育系统对网络传输的要求，指出只有流媒体技术才能较好地解决多媒体信息在中低带宽网上的传输问题，从而引入了流媒体的概念，随后简要介绍了微软公司的Windows Media的核心高级系统格式ASF，最后具体讲述了在网络课件制作过程中，利用流媒体技术实现音视频文件与网页内容同步的方法和步骤。     

无线局域网视频流组播优化机制

针对网络电视业务的802.11无线局域网数据传输问题,提出一种视频流组播优化机制,基于视频帧区分的方法,对关键帧I帧采用可靠组播机制传输,对非关键的B帧和P帧采用组播机制传输。仿真结果表明,该机制可以在丢帧率和数据延迟之间取得较好的折中,尤其是在无线网络带宽不足的情况下,能够有效提高数据传输后视频的观看质量。     

Optimized scalable cache management for video streaming system

An important research issue in video streaming is how to efficiently utilize the network resources to provide clients instant access to multiple video objects. Caching strategy and transmission scheme are the two essential points inside the video streaming framework. Recent research efforts on them are not sufficient due to their inflexible support for scalable encoded video streams and heterogeneous requests from clients. In this paper, we propose an optimized caching strategy (OCS) and a scalable transmission scheme (STS) for scalable coded video streaming. By exploring the characteristics of video streaming workload and system design objectives, OCS and STS work efficiently to minimize both network bandwidth cost and user access latency. Firstly, we analyze the caching problem for the proxy-assisted video streaming system and derive a maneuverable caching scenario. Secondly, we develop an efficient transmission scheme for scalable coded videos. Thirdly, we formulate a multi-objective optimization model with closed-form expressions to obtain the optimized caching strategy. Finally, with designed algorithms, an excellent compromise between two competing objectives (minimizing the bandwidth cost and the access latency) is achieved. We start our evaluation by studying the optimized caching strategy for a single video object. Then we apply the strategy to multiple video objects and illustrate the tradeoff between the optimization objectives. Our evaluation results show that compared with other caching strategies, the proposed optimized scalable caching strategy can achieve a significant reduction in bandwidth cost with even a small proxy cache size. Meanwhile, the best performance (in terms of bandwidth cost) is obtained together with the proposed scalable batch-patching transmission scheme.

Architecture for video streaming application on heterogeneous platform

In this paper, we propose a new architecture, which is an efficient streaming media player application on heterogeneous platform. The streaming library can be used in design for reducing the memory bandwidth on processing RTSP/RTP/RTCP network protocols. And the proposed improvement has to do with the I-frame encoding alone. The architecture can receive higher rate for data transfer and packet loss in embedded system. The framework of the key components is able to adopt Direct Memory Access to reduce the time-consumption resulted from the communication between the dual cores. On the other hand, the approach of the dynamic quality adaption improves the video bitstream by periodically adjusting the values of encoding quality parameters. Through the experiment results, it is evident that the new video streaming architecture greatly enhances the coding efficacy. Our experimental results present that the decoding/encoding speed of the dual-core CPU embedded with Direct Memory Access is enhanced up to 50 %, and its usage of CPU resources and memory bandwidth are 50 % lower than that of the popular JRTPLIB.     

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。     

A portable medical system using real-time streaming transport over 3G wireless networks

The paper proposes architecture for the software implementation of a multimedia, tele-medicine system. It considers video streaming from both video servers in hospitals and webcams localized to patients. It also considers transmission of vital bio-signs, such as heart rates and blood pressure, etc. All these data are transmitted over a 3G-wireless communication system to various client devices (hand-held devices, such as PDAs) used by physicians and nurses. Our video codec is a software implementation of the MPEG-4 standard, compression rate at about 1/24 sizes suited for available transmitting bandwidth. Moreover, our design, which also integrates the processing of heart sounds, supports a 44.1 KHz sampling rate and a 16-bit representation required about 11 kbps bandwidth. At the same time, in the streaming process, we propose a congestion control scheme to reduce packet losses.     

应用层组播节点流媒体调度算法

针对终端转发机制存在的延迟问题和传输率波动问题,提出一种应用层组播节点流媒体调度算法,通过采用组播节点的缓冲延迟和视频编码预测信息,减弱流视频的突发性高带宽需求,从而实现实时流率平滑传输,以提供稳定的流视频服务。仿真实验结果表明,该算法是有效可行的。     

IEEE 802.11e网络中传输可分级视频流的调度方案

在保证可分级视频流延时要求的情况下,为了有效提高其在无线网络中传输的带宽利用率,提出了一种新的调度方案。该方案利用可分级视频流的分解特性以及不同的流采用不同的调度周期来提高带宽利用率。数值结果表明该方案非常有效,特别是当物理层传输速率较大的时候,其有效性更加明显。     

基于MPEG-4的流媒体服务器端缓冲区管理

服务器端缓冲技术是流媒体系统中常用的一种应用控制技术，能够平滑网络抖动，减少数据丢失，提高客户端视频播放质量。该文的缓冲区管理增加了码率控制的功能，控制策略能进一步提高视频质量，特别适合于系统资源有限、带宽窄或强实时性的视频流式传输。     

基于区分服务的流媒体传输模型

流媒体在网络上的应用经常会受到数据包丢失或错误以及网络带宽资源不足的干扰,使得接收方播放质量受到严重影响。本文建立了一种适合流媒体传输的区分服务模型,该模型能够使高优先级数据流（实时流媒体数据流）占用更多的带宽。仿真结果表明：该策略能使流媒体数据流获得较高的吞吐量和较低的丢包率,有效提高流媒体传输的可靠性和实时性。     

基于区分服务的流媒体传输模型

流媒体在网络上的应用经常会受到数据包丢失或错误以及网络带宽资源不足的干扰,使得接收方播放质量受到严重影响。本文建立了一种适合流媒体传输的区分服务模型,该模型能够使高优先级数据流(实时流媒体数据流)占用更多的带宽。仿真结果表明:该策略能使流媒体数据流获得较高的吞吐量和较低的丢包率,有效提高流媒体传输的可靠性和实时性。     

Frequent layer switching for perceived quality improvements of coarse-grained scalable video

Scalable video is an attractive option for adapting the bandwidth consumption of streaming video to the available bandwidth. Fine-grained scalability can adapt most closely to the available bandwidth, but this comes at the cost of a higher overhead compared to more coarse-grained videos. In the context of VoD streaming, we have therefore explored whether a similar adaptation to the available bandwidth can be achieved by performing layer switching in coarse-grained scalable videos. In this approach, enhancement layers of a video stream are switched on and off to achieve any desired longer term bandwidth. We have performed three user studies, two using mobile devices and one using an HDTV display, to evaluate the idea. In several cases, the far-from-obvious conclusion is that layer switching is a viable way of achieving bit-rate savings and fine-grained bit-rate adaptation even for rather short times between layer switches, but it does, however, depend on scaling dimensions, content and display device.