基于PXA-255的AVS_M实时视频服务器的设计

设计并实现了一款嵌入式实时视频服务器,该服务器是基于PXA-255处理器芯片,利用AVS_M编码技术和RTP/RTCP传输协议进行视频采集、编码和传输.介绍了多种方法在代码实现层次上分别对AVS_M编码算法和系统遗行优化.实验结果表明,经过优化之后AVS M的编码速度有了较明显的提高,能够达到实时性的要求,通过网络传输在客户端能得到较清晰的图像,可以满足视频应用的需要.     

3G无线流媒体技术在水利监控的应用

随着3G网络的商用,流媒体技术也拓展到无线领域,可适用于监控等多种业务。介绍了流媒体的概念,分析了流媒体编解码和嵌入式视频Web服务器技术,重点就3G流媒体在水利监控中的应用和水利3G监控系统的组成进行阐述和说明。将3G流媒体应用于水利监控,可节省人力和监视设备,推进水利视频监控系统向智能化的综合管理系统发展。     

基于iSCSI技术的流媒体存储系统研究

本文简要分析了视频监控领域流媒体存储的主要特点,提出了两种使用iSCSI协议实现实时流存储系统的结构,针对使用流媒体服务器的结构,进行了系统原型设计和实现,并对其性能进行了测试。测试结果表明,原型系统存储性能满足高清网络视频监控系统的需求。     

架构在视频门禁系统中的应用——基于JMF的流媒体服务器

设计了一个基于JMF技术的流媒体服务器架构,并应用于视频门禁系统中。该架构在逻辑上是BS三层结构,采用组播进行数据传输。系统采用RTP/RTCP协议实现MPEG实时流媒体服务,在IP网络中运行良好。     

嵌入式移动视频监控服务系统的研究与实现

为了满足移动终端用户对视频监控服务的需求,提出了符合第三代合作伙伴计划(3GPP)相关协议的无线网络视频监控流媒体服务系统.系统采用具有MPEG4硬件压缩功能的芯片为主要构件,以Coldfire 5272嵌入式微处理器和uClinux嵌入式操作系统为基础,并应用开源LIVE555媒体库实现RTP/RTCP/RTSP等相关协议.还讨论了实际工程实现中的一些具体问题,如内网穿透,扩展云台控制等.     

基于SIP、RTP／RTCP和RTSP协议的视频监控系统

从流媒体协议入手,描述会话发起协议SIP（Session Initiation Protocol）、实时传输协议RTP（Real time Transport Protocol）、实时传输控制协议RTCP（RTP Control Protocol）和实时流传输协议RTSP（Real Time Streaming Protocol）的原理以及它们在IP单播或多播网络上的通信过程。在此基础上,进一步分析RTP/RTCP和RTSP协议的关系,并对基于RTP/RTCP和RTSP协议的流媒体服务器进行设计。流媒体服务器是视频监控系统的核心部分,采用C/S结构,服务器和客户端之间的多媒体数据之间的传递都在这一部分完成。在基于RTP/RTCP和RTSP协议的流媒体服务器的基础上,使用SIP协议让用户和服务器建立会话连接,并在流媒体服务器上进行多媒体数据的传递,从而设计出基于SIP、RTP/RTCP和RTSP协议的视频监控系统。     

基于HLS协议的视频点播系统客户端设计

本文介绍了基于HTTP Live Stream(简称HLS)的流媒体技术,包括协议原理,以及MPEG-2 TS流的封装及传输。并描述了一种基于HLS协议的视频点播系统的设计实现,包括状态机的原理,JSON封装的文件列表、视频信息的解析等。     

嵌入式流媒体服务器的设计和实现

为了解决嵌入式环境下的视频传输,提出了一个嵌入式流媒体服务器的应用设计方案.采用了流媒体传送技术、控制协议技术、进程间通信技术,使用开放源码流媒体服务器live555项目设计和实现了一个嵌入式流媒体服务器,解决了四个技术问题:管道读写视频操作问题,服务器传送视频控制字问题,服务器与客户端视频播放控制协议问题,流媒体服务器异常退出后恢复问题.该流媒体服务器能够正确传输视频数据,客户端能够播放实时视频,播放画面图像质量高、时延小、稳定可靠.     

基于MPEG-4的嵌入式流媒体服务器设计

介绍了基于MPEG-4硬件实时编码器的嵌入式流媒体服务器的设计,阐述了系统的硬件组成,并从MPEG-4视频流封装、RTP/RTCP协议实现、开源RTSP协议库的应用和Web服务器的构建等方面介绍了软件系统的具体实现过程.此外,还对实时传输中所涉及的时间戳和QoS机制的实现方法进行了介绍.实验结果表明,该系统具有丢包率低和容错能力强等特点,适用于移动视频监控等实际应用场合.     

基于P2P技术的流媒体转发服务器的设计与实现

近年来,远程视频监控系统在各个领域有着广泛的应用,伴随着客户数的不断增多和要求的不断提高。视频服务器和网络带宽的压力越来越大。为缓解这些压力,文章介绍了一种流媒体转发服务器的设计,在客户端配置流媒体转发服务器,引入P2P网络技术,突破了传统视频监控系统的带宽瓶颈。最后实现了流媒体转发服务器的结构和算法设计,并展示了其功能。     

Peer Assisted Video Streaming With Supply-Demand-Based Cache Optimization

In this paper, we consider a hybrid P2P video on-demand architecture that utilizes both the server and the peer resources for efficient transmission of popular videos. In our system architecture, each peer dedicates some cache space to store a particular segment of a video file as well as some of its upload bandwidth to serve the cached segment to other peers. Peers join the system and issue a streaming request to a control server. Control server directs the peers to streaming servers or to other peers who have the desired video segments. Control server also decides which peer should cache which video segment. Our main contribution in this paper is to determine the proper caching strategies at peers such that we minimize the average load on the streaming servers.      

SMTVS:一种基于H.264的手机电视系统

手机电视系统必须能够适应网络和客户端的异构性、无线信道的多变性等特点.提出一种手机电视系统SMTVS,流媒体服务器在不同码率的H.264视频流之间进行切换以适应网络状况的变化;代理服务器之间构成一个内容分送网络,视频数据通过应用层组播的方式传输到各个代理服务器,降低了服务器的负载,提高了网络资源利用率;代理服务器接收到视频数据之后,针对无线链路的状况对数据进行处理后再发送到客户端,以适应最终用户的不同需求;客户端根据网络状况来动态调整播放速率,避免显示缓冲区下溢和上溢.通过流媒体服务器、代理服务器以及客户端的协作,实现了视频数据在无线信道上的自适应传输.     

Practical design of a proxy agent to facilitate adaptive video streaming service across wired/wireless networks

Thanks to the growing of the wireless networks, the video streaming application becomes a ubiquitous joyful service. In a wireless communication network environment, the service traffic spans across the wired and wireless domains. In this article, we propose a practical design of a proxy agent - SPONGE (Stream Pooler Over a Network Graded Environment) sitting between the wireless User Equipments (UEs) and the video streaming server to facilitate the adaptive video streaming service across wired/wireless networks. To make the wireless streaming service more efficient, an input video session would be encoded as multiple qualities of video streams so that UEs with a similar receiving condition can share streams with the same service quality via SPONGE. SPONGE can alleviate the direct load on the original stream broadcasting server. Meanwhile, it can make each UE get an adaptive streaming service according to the network conditions of the UE by a reduced network condition feedback latency. Our theoretical analysis and simulation results show that SPONGE can help wireless streaming users get a smooth and better playback quality by a quick and accurate reaction to the network condition.     

Fast-path I/O architecture for high performance streaming server

In a disk-network scenario where expensive data transfers are the norm, such as in multimedia streaming applications, for example, a fast-path I/O architecture is generally considered to be “good practice.” Here, I/O performance can be improved through minimizing the number of in-memory data movements and context switches. In this paper, we report the results of the design and implementation of a high-performance streaming server using cheap hardware units assembled directly on a test card (i.e., NS card). The hardware part of our architecture is open to further reuse, extension, and integration with other applications even in the case of inexpensive and/or faster hardware. From the viewpoint of software-aided I/O, we offer Stream Disk Array (SDA) for scatter/gather-style block I/O, EXT3NS multimedia file system for large-scale file I/O, and interoperable streaming server for stream I/O.     

Adaptive interface selection over cloud-based split-layer video streaming via multi-wireless networks

As mobile devices such as tablet PCs and smartphones proliferate, the online video consumption over a wireless network has been accelerated. From this phenomenon, there are several challenges to provide the video streaming service more efficiently and stably in the heterogeneous mobile environment. In order to guarantee the QoS of real-time HD video services, the steady and reliable wireless mesh is necessary. Furthermore, the video service providers have to maintain the QoS by provisioning streaming servers to respond the clients’ request of different video resolution. In this paper, we propose a reliable cloud-based video delivery scheme with the split-layer SVC encoding and real-time adaptive multi-interface selection over LTE and WiFi links. A split-layer video streaming can effectively scale to manage the required channels on each layer of various client connections. Moreover, split-layer SVC model brings streaming service providers a remarkable opportunity to stream video over multiple interfaces (e.g. WiFi, LTE, etc.) with a separate controlling based on their network status. Through the adaptive interface selection, the proposed system aims to ensure the maximizing video quality which the bandwidth of LTE/WiFi accommodates. In addition, the system offers cost-effective streaming to mobile clients by saving the LTE data consumption. In our system, an adaptive interface selection is developed with two different algorithms, such as INSTANT and EWMA methods. We implemented a prototype of mobile client based on iOS particularly by using iPhone5S. Moreover, we also employ the split-layer SVC encodes in streaming server-side as the add-on module to SVC reference encoding tool in a virtualized environment of KVM hypervisor. We evaluated the proposed system in an emulated and a real-world heterogeneous wireless network environments. The results show that the proposed system not only achieves to guarantee the highest quality of video frames via WiFi and LTE simultaneous connection, but also efficiently saves LTE bandwidth consumption for cost-effectiveness to client-side. Our proposed method provides the highest video quality without deadline misses, while it consumes 50.6% LTE bandwidth of ‘LTE-only’ method and 72.8% of the conventional (non-split) SVC streaming over a real-world mobile environment.     

AVS-M: From Standards to Applications

AVS stands for the Audio Video coding Standard Workgroup of China, who develops audio/video coding standards as well as system and digital right management standards. AVS-M is the AVS video coding standard targeting for mobile multimedia applications. Besides the coding specification, AVS also developed the file format and Real-time Transport Protocol （RTP） payload format specifications to enable the application of AVS-M video in various services. This paper reviews the high-level coding tools and features of the AVS-M coding standard as well as the file format and payload format standards. In particular, sixteen AVS-M high-level coding tools and features, which cover most of the high-level topics during AVS-M standardization, are discussed in some detail. After that, the error resilience tools are briefly reviewed before the file format and RTP payload format discussions. The coding efficiency and error resiliency performances of AVS-M are provided finally. H.264/AVC has been extensively used as a comparison in many of the discussions and the simulation results.     

Server side,play buffer based quality control for adaptive media streaming

Existing media streaming protocols provide bandwidth adaptation features in order to deliver seamless video streams in an abrupt bandwidth shortage on the networks. For instance, popular HTTP streaming protocols such as HTTP Live Streaming (HLS) and MPEG-DASH are designed to select the most appropriate streaming quality based on client side bandwidth estimation. Unfortunately, controlling the quality at the client side means the effectiveness of the adaptive streaming is not controlled by service providers, and it harms the consistency in quality-of-service. In addition, recent studies show that selecting media quality based on bandwidth estimation may exhibit unstable behavior in certain network conditions. In this paper, we demonstrate that the drawbacks of existing protocols can be overcome with a server side, buffer based quality control scheme. Server side quality control solves the service quality problem by eliminating client assistance. Buffer based control scheme eliminates the side effects of bandwidth based stream selection. We achieve this without client assistance by designing a play buffer estimation algorithm. We prototyped the proposed scheme in our streaming service testbed which supports pre-transcoding and live-transcoding of the source media file. Our evaluation results show that the proposed quality control performs very well both in simulated and real environments.     

基于P2P的用户生产内容视频资源查找策略

现有用户生产内容(UGC)类视频系统通常采用C/S架构设计,导致了视频服务器极大的带宽压力。提出一种采用对等网(P2P)的在线短视频查找策略——FastSearch,其目的是利用视频资源之间的关联关系进行视频资源定位,以显著提高点播节点之间的视频分享效率并降低对视频服务器的带宽需求。实验表明FastSearch具备良好的视频数据源节点查找能力,集成了该查找策略的短视频系统能有效减少对视频服务器的带宽消耗。     

3G流媒体服务器的研究与实现

随着移动无线网络和流媒体的飞速发展,基于无线网络的实时视频传输成为研究热点.以此为背景,采用了MPEG-4标准压缩视频流,使用RTP/RTCP传输层协议和RTSP/SDP会话层协议,应用了一种基于RTP/RTCP的端到端的自适应反馈控制算法,研究和开发了一个基于无线网络CDMA2000 1X的流媒体服务器系统.