无线流媒体自适应链路层HARQ控制策略

无线网络动态的信道特性、高误码率和带宽有限等特点,使得在无线环境下为实时流媒体传输提供QoS保证面临更大的挑战;提出了一种用于无线实时流媒体传输的自适应链路层HARQ控制策略,针对不同的信道状况动态选择混合ARQ方案;该策略采用跨层设计的方法,在应用层采用自适应FEC策略,在视频源数据和冗余数据之间动态分配网络带宽;数学分析和仿真验证表明,该策略能使接收方获得最大的可播放帧率,有效地提高流媒体传输的可靠性和实时性。     

自适应流媒体传输方案研究及其应用

提出了一种自适应流媒体传输方案，根据网络状况调整视频数据的发送速率和视频流的码率，以保证视频数据顺利及时的传输到客户端，使客户端能够顺利进行高质量的媒体播放。该方案涵盖了码率整形、拥塞控制和视频质量自适应等功能模块及其相互关系，各功能模块可以依据应用需求选择算法加以具体实现，从而提高了方案的可扩展性和灵活性。所以该方案不依赖于具体的视频编码标准和网络协议，适用范围较广。文中还基于实际流媒体服务器给出了该方案的一个实际应用，点播测试实验汪明该方案是有效的。     

基于代理缓存的流媒体动态调度算法研究

该文研究了在Internet环境下通过代理服务器将流媒体从源服务器传输到多个客户端时的骨干网络及服务器带宽消耗问题．在分析了传统多媒体流动态调度算法不足的基础上,提出了基于代理服务器协助的补丁预取与服务调度算法(P^3S^2A)．由代理服务器通过单播连接从源服务器中获取流媒体数据,然后通过组播方式转发给客户端．同时根据当前客户请求到达的分布状况,代理服务器为后续到达的客户请求进行补丁预取及缓存．理论分析及实验结果表明,与传统的动态调度方法相比,该文提出的算法能够在不消耗更多的缓存空间的情况下,更有效地节省骨干网络的带宽资源,特别是在访问请求强度较高的情况下,效果更为突出。     

基于J2ME的流媒体视频服务系统的设计与实现

为了突破目前主流系统的平台局限性,构建了一个基于Darwin开源服务器和J2ME技术开发的手机客户端的流媒体视频服务系统.该系统是典型的C/S架构,服务器端同时支持FreeBSD、Linux、Solaris、Windows等多个操作系统,客户端可以运行在支持Java环境的不同品牌的手机中,免去大量的平台移植工作.手机用户通过GPRS上网后,在一定的带宽环境下就可以在线欣赏到连续不断的高品质音频和视频节目.     

J2ME的手机视频点播系统设计

讲解基于J2ME技术的手机视频点播系统的设计方法。分析了J2ME技术的特点,根据网络视频流媒体技术,设计出手机视频点播系统模型,分析阐明实现手机视频点播系统客户端和服务器的关键技术,给出关键代码。     

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.     

手机电视发展现状及障碍

一、我国手机电视发展情况 移动视频，顾名思义，就是通过移动电信网络实现的，在点对点或点对多点情况下传送声音、图像、数据文件的实时性交互业务。而所谓手机电视业务，就是利用具有操作系统和视频功能的智能手机观看电视的业务，属于流媒体服务的一种。专家介绍，在未来的视频电话、视频会议、流媒体视频服务、视频信箱、视频消息等移动视频服务中，移动流媒体视频服务无疑将成为主流。     

一种无线实时流媒体增强型自适应FEC控制机制

无线网络动态的信道特性和带宽有限等特点,使得在无线环境下为流媒体应用提供QoS保证面临更大的挑战。提出一种用于无线实时流媒体传输的增强型自适应前向纠错控制策略,以提高接收方的播放质量。该策略采用跨层设计的方法,根据当前的网络状态,自适应地调整MPEG视频帧的发送速率,在视频源数据和冗余数据之间动态分配网络带宽。仿真结果表明,该策略能使接收方获得最大的可播放帧率,有效提高流媒体传输的可靠性和实时性。     

Kalman滤波的自适应链路层FEC控制策略

无线网络动态的信道特性、高误码率和带宽有限等特点,使得在无线环境下为实时流媒体传输提供QoS保证面临更大的挑战。提出一种用于无线实时流媒体传输的自适应链路层FEC控制策略,以显著提高接收方的播放质量。该策略采用跨层设计的方法,基于Kalman滤波器预测当前的网络状态,考虑物理带宽限制和GOP可解码帧数的特性自适应地调整FEC参数N;另一方面,在应用层采用自适应FEC策略,在视频源数据和冗余数据之间动态分配网络带宽。数学分析和仿真验证均表明,该策略能使接收方获得最大的可播放帧率,有效地提高了流媒体传输的可靠性和实时性。     

基于Android的家居视频监控系统的设计

本文叙述了基于Android的家居视频监控系统的设计过程。本系统将通过WIFI连接的摄像头采集到的视频数据传给视频服务器,服务器经过H.264格式编码后用RTP协议进行封包,利用UDP传输协议以无线信号的形式实时地发送到基于Android操作系统的客户端。另外,服务器根据客户端APP的预警设置,进行实时录像,并给已绑定的客户端发警报短信。     

Throughput optimization for video streaming proxy servers based on video staging

A video streaming proxy server needs to handle hundreds of simultaneous connections between media servers and clients. Inside, every video arrived at the server and delivered from it follows a specific arrival and delivery schedule. While arrival schedules compete for incoming network bandwidth, delivery schedules compete for outgoing network bandwidth. As a result, a proxy server has to provide sufficient buffer and disk cache for storage, together with memory space, disk space and disk bandwidth. In order to optimize the throughput, a proxy server has to govern the usage of these resources. In this paper, we first analyze the property of a traditional smoothing algorithm and a video staging algorithm. Then we develop, based on the smoothing algorithm, a video staging algorithm for video streaming proxy servers. This algorithm allows us to devise an arrival schedule based on the delivery schedule. Under this arrival and delivery schedule pair, we can achieve a better resource utilization rate gracefully between different parameter sets. It is also interesting to note that the usage of the resources such as network bandwidth, disk bandwidth and memory space becomes interchangeable. It provides the basis for inter-resource scheduling to further improve the throughput of a video streaming proxy server system.

一种基于Sever和Proxy流媒体流行性的Caching策略

1 概述经过了2000、2001两年的社区宽带网建设的高速发展后,摆在中国ISP们面前的任务是如何在已建成的宽带网上开展增值服务,许多ISP尝试在宽带网上开展流媒体(Streaming Media)服务,如视频点播VOD(Video On-Demand)系统。然而,流媒体对网络带宽和实时性的要求使得流服务器必须能够进行端对端(End-to-End)的拥塞控制和质量调整,由于     

种基于Sever和Proxy流媒体流行性的Caching策略

It is expected that by 2003, continuous media will account for more than 50% of the data available on origin servers. This will provoke a significant change in Internet workload, due to the high bandwidth requirements and the long-lived nature of digital video, streaming server loads and network bandwidths are proving to be major limiting factors. Aiming at the characteristic of broadband network in a residential area, we propose a popularitybased on server-proxy caching strategy for streaming media. According to a streaming media popularity on streaming server and proxy, this strategy caches the content of this streaming media partially or completely, and plays an important role in decreasing server load, reducing the traffic from streaming server to proxy, and improving the startup latency of the client.     

Loopback: exploiting collaborative caches for large-scale streaming

In this paper, we propose a Loopback approach in a two-level streaming architecture to exploit collaborative client/proxy buffers for improving the quality and efficiency of large-scale streaming applications. At the upper level we use a content delivery network (CDN) to deliver video from a central server to proxy servers. At the lower level a proxy server delivers video with the help of collaborative client caches. In particular, a proxy server and its clients in a local domain cache different portions of a video and form delivery loops. In each loop, a single video stream originates at the proxy, passes through a number of clients, and finally is passed back to the proxy. As a result, with limited bandwidth and storage space contributed by collaborative clients, we are able to significantly reduce the required network bandwidth, I/O bandwidth, and cache space of a proxy. Furthermore, we develop a local repair scheme to address the client failure issue for enhancing service quality and eliminating most required repairing load at the central server. For popular videos, our local repair scheme is able to handle most of single-client failures without service disruption and retransmissions from the central server. Our analysis and simulations have shown the effectiveness of the proposed scheme.     

基于H264的嵌入式视频服务器的设计

本文介绍了基于H264的嵌入式视频服务器的设计，重点阐述了，嵌入式操作系统，视频服务管理系统，视频服务器在监控中的解决方案，最新的压缩算法H264，以及流媒体传输。     

Proxy-assisted periodic broadcast for video streaming with multiple servers

Large scale video streaming over the Internet requires a large amount of resources such as server I/O bandwidth and network bandwidth. A number of video delivery techniques can be used to lower these requirements. Periodic broadcast by a central server combined with proxy caching offers a significant reduction of the aggregate network and server I/O bandwidth usage. However, the resources available to a single server are still limited. In this paper we propose a system with multiple geographically distributed servers. The problem of multiple servers for periodic broadcast is quite different from the problem of object location for multiple web servers. Multiple servers offer increased amount of resources and service availability and may potentially allow a further reduction of network bandwidth usage. On the other hand, the benefit of periodic broadcast mostly comes from high demand videos. With multiple servers holding a video, the demand of the video at each server is reduced. Therefore, it is a challenge to use multiple servers efficiently. We first analyze the dependence of the resource requirements on the number and locations of the servers. Based on the character of the function describing such a dependence, we formulate and solve the problem of video location and delivery, in a way that minimizes resource usage. We explore a trade-off between network and I/O bandwidth requirements. We evaluate our proposed solutions through a number of tests.

Frame Selection for Dynamic Caching Adjustment in Video Proxy Servers

By caching video data, a video proxy server close to the clients can be used to assist video delivery and alleviate the load of video servers. We assume a video can be partially cached and a certain number of video frames are stored in the proxy server. In our setting, the proxy server is allowed to cache the passing data from the video server. A video provides several options (levels) in terms of bandwidth requirement over the server-proxy path. For each video, the proxy server decides to cache a smaller amount of data at a lower level or to accumulate more data to reach a higher level. The proxy server can dynamically adjust the cached video data by choosing an appropriate level based on the network condition or the popularity of the video. We propose a frame selection scheme, Dynamic Chunk Algorithm, to determine which frames are to be cached in the proxy server for the dynamic caching adjustment scenario. The algorithm guarantees the rate constraint over the server-proxy path to be satisfied for each level. This approach also maintains the set of cached frames at a higher level as a superset of the cached frames at a lower level. Hence, it enforces the proxy server to simply cache more data without dropping frames when it intends to reduce network bandwidth consumption for a video and vice versa.     

Optimized streaming media proxy and its applications

Multimedia streaming is one of the most popular services on the current Internet. However, the major problem hinders streaming media applications is the network bandwidth. In this paper, we put forward a optimized streaming proxy system and think of utilizing it in peer-to-peer (P2P) applications. The main contribution of our proxy system is RTP segments splicing, prefix caching size determination and prefetching techniques, which are detailed discussed in this paper. By validating our implementation, the experimental results show that the streaming proxy can effectively contribute to reduce the server and backbone network load, thus achieve improved media quality and scalability. In addition, P2P network is a fascinate way for Internet resource sharing, many of researchers are devoting to research on P2P-based client communications. In our project, we make use of our proxy prototype into the streaming sharing over P2P network, each peer node just like a lightweight proxy between the server and the target peers. The real-time video sharing (RVS) system efficiently utilizes network bandwidth between peer clients through combining with our proxy as expected.     

Parallel video streaming optimizing network throughput

In the Internet, video streaming services, in which users can enjoy videos at home, are becoming popular. Video streaming with high definition TV (HDTV) or ultra high definition video (UHDV) quality will be also provided and widely demanded in the future. However, the transmission bit-rate of high-quality video streaming is quite large, so generated traffic flows will cause link congestion. In the Internet, routes that packets take are determined using static link weights, so the network productivity, i.e., the maximum achievable throughout by the network, is determined by the capacity of a bottleneck link with the maximum utilization, although utilizations of many links remain low level. Therefore, when providing streaming services of rich content, i.e., videos with HDTV or UHDV quality, it is important to flatten the link utilization, i.e., reduce the maximum link utilization. We propose that ISPs use multiple servers to deliver rich content to balance the link utilization and propose server allocation and server selection methods for parallel delivery. We evaluate the effect of parallel delivery using 23 actual commercial ISP networks.     

一种保证初始数据完整性的实时视频流分发插件

在视频监控联网系统中进行实时监控时,如果监控客户端收到的初始视频数据不完整会出现初始播放画面花屏的问题.基于开源多媒体框架GStreamer,针对H.264编码标准,设计并实现了一种实时视频流分发插件.该插件使用随机创建的请求型source衬垫用于视频数据的分发,并通过缓存当前IDR帧组的方法确保发送初始视频数据的完整性.该插件可应用于流媒体服务器当中,解决实时监控时初始画面花屏的问题.实验结果表明,应用该插件的流媒体服务器能够高效分发实时视频数据并保证初始播放画面完整,对提升实时监控效果有着明显的作用.