Content-adaptive wireless streaming of instructional videos

Video streaming over wireless networks is becoming increasingly important for a variety of applications. To accommodate the dynamic change of wireless network bandwidths, Quality of Service (QoS) scalable video streams need to be provided. This paper presents a system of content-adaptive streaming of instructional (lecture) videos over wireless networks for E-learning applications. We first provide a real-time content analysis method to detect and extract content regions from instructional videos, then apply a “leaking-video-buffer” model to adjust QoS of video streams dynamically based on video content. In content-adaptive video streaming, an adaptive feedback control scheme is also developed to transmit properly compressed video streams to video clients not only based on network bandwidth, but also based on video content and the preferences of users. Finally, we demonstrate the scalability and content adaptiveness of the proposed video streaming system with experimental results on several instructional videos.     

Extracting content from instructional videos by statistical modelling and classification

This paper presents a robust approach to extracting content from instructional videos for handwritten recognition, indexing and retrieval, and other e-learning applications. For the instructional videos of chalkboard presentations, retrieving the handwritten content (e.g., characters, drawings, figures) on boards is the first and prerequisite step towards further exploration of instructional video content. However, content extraction in instructional videos is still challenging due to video noise, non-uniformity of the color in board regions, light condition changes in a video session, camera movements, and unavoidable occlusions by instructors. To solve this problem, we first segment video frames into multiple regions and estimate the parameters of the board regions based on statistical analysis of the pixels in dominant regions. Then we accurately separate the board regions from irrelevant regions using a probabilistic classifier. Finally, we combine top-hat morphological processing with a gradient-based adaptive thresholding technique to retrieve content pixels from the board regions. Evaluation of the content extraction results on four full-length instructional videos shows the high performance of the proposed method. The extraction of content text facilitates the research on full exploitation of instructional videos, such as content enhancement, indexing, and retrieval.

Enhancing wireless video streaming using lightweight approximate authentication

In this paper, we propose a novel lightweight approximate authentication algorithm that provides efficient protection for wireless video streaming where attacks on the stream are possible, but classical integrity protection algorithms are impractical because bit errors occur naturally. The benefits of the proposed algorithm over other algorithms are fast execution and small message authentication code size. Moreover, the approximate authentication supports error resilient video decoding by dropping seriously damaged packets, thus improving the perceived quality of the video stream. The performance of the algorithm is demonstrated via numerical analysis, simulations and measurements over modeled and real wireless channels.     

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。     

Optimized P2P streaming for wireless distributed networks

The future Internet will support pervasive applications and communications models that require end-nodes cooperation, such as fog computing and machine-to-machine communications. Among the many applications, also video streaming can be provided with a cooperative and peer-to-peer approach. Cooperative distribution requires building a distribution overlay on top of the physical topology (the underlay). This work proposes an optimized, cross-layer approach to build this overlay minimizing the impact on the underlay. We design an optimal strategy, which is proven to be NP-complete, and thus not solvable with a distributed, lightweight protocol. The optimal strategy is relaxed exploiting the knowledge on the betweenness centrality of the nodes in the underlay topology, obtaining two easily implementable solutions applicable to any link-state protocol for distributed wireless mesh networks. The additional introduction of heuristic improvements further optimizes the performance in real network scenarios. Extensive simulation results support the theoretical findings using three different network topologies. They show that the relaxed implementations are reasonably close to the optimal solution, and provide vast gains compared to the traditional overlay topologies that peer-to-peer applications build.     

新颖的实时视频流传输模式

视频传输需要消耗大量的带宽和占用服务器的大量计算资源,为了解决同时传输的视频流数目受到限制的问题,提出了一种新颖的视频流传输框架,多个网络视频服务器组成一个组来共同为多个视频流用户提供服务.在此框架下,研究了一个新的问题——最大化视频流,目标是最大化同时传输的视频流数量.设计了一个启发式的高效算法,与传统的几种视频流传输模式相比,该方法可以支持更多的视频流.     

一种适用于无线网络的流媒体传输机制

为保证无线网络中多媒体数据的传输质量,提出了一种适用于无线网络的流媒体传输机制（WMTCC）。该机制通过发送探测报文区分网络拥塞丢包和链路误码随机丢包,准确判断网络的拥塞状况,实施发送速率调节,保证了流媒体服务质量(QoS)。由于准确区分出无线链路误码丢包,该机制在链路误码率较高时能维持较高的网络吞吐量。仿真实验结果显示在高误码率无线网络中,该机制可以获得更高的吞吐量和更大的拥塞窗口,并且发送速率的变化更加平滑。     

面向视频流媒体的应用层多播技术研究 *

主要关注面向视频流媒体的应用层多播（ALM）技术的研究近况。首先总结了ALM的研究概况和分 类,重点研究了几个针对视频流媒体应用而提出的ALM协议和框架,讨论其中用到的一些前沿技术,分析这些 协议的优缺点,同时给出一些改进思路。最后展望了ALM视频流媒体技术的未来研究方向。     

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。     

无线实时流媒体传输性能的跨层优化设计

提出一种用于无线实时流媒体传输的优化设计策略,以提高接收方的播放质量。该策略采用跨层设计的方法,利用泊松过程分析链路层数据帧的丢失,同时把链路层最大重传次数映射到端到端时延和丢包率的计算中,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。仿真实验结果表明,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。     

视频流自适应传输技术研究

对当前视频流技术所采取的各种压缩算法及标准、传输协议、拥塞控制等技术进行了总结与分析,在此基础上对IP网络上的视频流自适应传输技术进行了研究,建立了实现该技术的框架。此技术框架综合了实时的视频自适应编码技术和有效的带宽自适应传输技术。实验结果表明,在对视频流的实时性要求高的应用上具有较突出的优势。     

Loss tolerant video streaming authentication in heterogeneous wireless networks

Multicast video streaming in heterogeneous networks undergoes to very different physical constraints, in fact, such networks are characterized by different QoS parameters, involving one or more transcoding process between the sender and the receivers. Video streaming authentication algorithms must be robust to transcoding processes and must guarantee the copyright of the video owner/producer. We propose a real-time video streaming authentication algorithm that can guarantee the copyright of the video owner and that we prove to be robust to packet loss and transcoding processes.     

V3: A vehicle-to-vehicle live video streaming architecture

We propose V3, an architecture to provide a live video streaming service to driving vehicles through vehicle-to-vehicle (V2V) networks. V2V video streaming is challenging because: (1) the V2V network may be persistently partitioned; (2) the video sources are mobile and transient. V3 addresses these challenges by incorporating a novel signaling mechanism to continuously trigger vehicles into video sources. It also adopts a store-carry-and-forward approach to transmit video data in partitioned network environments. We first propose an initial design which supports video streaming to a single receiver. We then propose a multicasting framework that enables video streaming from multiple sources to multiple receivers. Simulation experiments demonstrate the feasibility of supporting V2V video streaming with acceptable performance.     

基于H.264可伸缩视频流的自适应媒体播放算法

为了应对H.264可伸缩视频编码（SVC）应用中网络特性的波动,提出了一种预测播放中断与缓冲区溢出风险进行及早调节的自适应媒体播放(AMP)算法。该算法估算网络流量与视频图像组（GOP）结构中各帧长度用于风险预测,通过K步调节过程实现良好的调节平滑性与速度,并利用SVC的可伸缩性尽量减少溢出带来的质量损失。仿真结果表明,该算法在抑制播放中断、处理缓冲区溢出与抖动性能等方面,优于现行的平滑AMP与常规AMP算法。     

基于模糊逻辑的Internet视频流拥塞控制

为了提高视频传输质量,在Internet上对视频流进行拥塞控制,即利用包发送和接收间隔时间（IPGs）代替丢包率作为拥塞指示,采用模糊逻辑拥塞控制策略（FLC）调整视频发送速率并用遗传算法优化模糊控制规则,提高了拥塞控制性能。仿真结果表明,与TFRC和RAP拥塞控制相比,由于FLC发送速率更平滑、带宽利用率更高,从而减少了丢包,提高了视频传输质量;另外,FLC能够与竞争的TCP流公平地分享带宽并对路由器缓冲区大小保持了很好的鲁棒性。     

流媒体技术在远程视频监控系统中的应用与实现

针对目前远程视频监控系统中视频信号进行远程传输所面临的问题和存在的不足,讨论了基于流媒体技术的新型远程视频监控系统的应用方案,提出了如何利用流媒体技术跨越地域限制实现远程视频传输的方法。     

Quality adaptive end-to-end packet scheduling to avoid playout interruptions in Internet video streaming systems

In Internet multimedia streaming, the quality of the delivered media can be adapted to the Quality of Service provided by the underlying network, thanks to encoding algorithms. These allow a fine grained enhancement of a low quality base layer at streaming time. The main objective that should be satisfied in such systems is to avoid the starvation of the decoding process and consequent playout interruptions. In this work, we tackle the problem using a control theoretic approach. In particular, we design and implement the novel end-to-end Quality Adaptive Scheduler for properly distributing the network available bandwidth among base and enhancement layers. The developed solution can be adopted in many contexts given that it has been designed without assumptions on the delivered media nor on the protocol stack. Anyway, to test its effectiveness, we have casted it in a H.264/AVC SVC based video streaming architecture for unicast Internet applications. The performance of the scheduler has been experimentally evaluated in both a controlled testbed and several “wild” Internet scenarios, including also UMTS and satellite radio links. Results have clearly demonstrated that our Quality Adaptive Scheduler is able to significantly improve the performance of the video streaming system in all operative conditions.     

基于无线网络环境下的移动流媒体系统的实现

随着现在无线网络质量的提高。以及终端增值业务的不断发展．通过终端实现收看电视节目、以及实现远程监控和电话会议将会成为最能吸引用户的业务．本文基于现有的无线网络环境．结合当前的图像压缩技术H．263与MPEG4，围绕如何建设流媒体平台．给出了其组网和系统集成方案。并对流媒体系统的内容管理、业务管理、计费管理做了论述。     

基于Flex、Red5和MongoDB的视频直播、录制及存储系统设计

为改善以往网络视频直播或点播过程中播放不流畅的情况和寻找大量视频数据的存储策略,提出了一种实时的视频直播、录制及存储系统的整体设计方案。利用开源的流媒体服务器Red5结合富互联网技术Flex实现直播和录制;通过开源NoSQL数据库MongoDB将录制的视频数据进行存储。实际测试结果表明,该平台能满足系统在多用户访问和数据存储方面的要求。     

P2P在线视频研究综述

P2P技术凭借其开放性、可扩展性和高性价比等优点成为了目前解决在线视频问题的有效手段之一。 虽然P2P技术在文件共享和IP语音等方面的应用已经基本趋于成熟,但其在在线视频领域的应用尚处于起步 阶段,还面临着许多需要解决的问题。对P2P在线视频进行了全面而深入的分析,首先介绍了网络广播分类及 体系结构设计,整理和总结了已有的关于P2P在线视频系统的测量研究结果,最后对于P2P在线视频信任和污 染攻击等安全问题进行了概述。