基于跨层设计的嵌入式无线视频监控系统实现

设计一种基于i．MX27的ARM9＋Linux系统组成的嵌入式无线视频监控系统。该系统采用H．264压缩编码和RTP／RTCP流媒体传输协议,实现了视频数据的压缩发送,同时在该系统上实现基于物理层网卡发送速率和RTP丢包率反馈信息相结合的跨层码率控制策略。测试和应用结果表明,该系统取得了良好的视频效果,具有很好的应用前景。     

无线视频传输的跨层动态映射算法

在IEEE 802.11e EDCA机制和基于场景的马尔可夫链模型基础上,提出跨层动态映射算法来改善无线视频传输的服务质量（QoS）。根据视频帧的重要性和网络的负荷情况,将来自应用层的视频帧信息动态地映射到MAC层中合适的队列中去,并且采用网络仿真工具NS2进行仿真,来比较IEEE 802.11e EDCA机制以及跨层动态映射算法。仿真结果表明跨层动态映射算法能明显提高传输后的视频质量。     

无线视频的一种码率控制方法

无线信道的高误码率对视频图像质量有很大的影响,前向纠错(FEC)和自动重发请求(ARQ)对于降低无线信道的误码率,提高图像质量有很好的效果。通过对FEC和ARQ方法的有效性分析,在TMN8的基础上提出一种简单的混合FEC/ARQ自适应模式选择码率控制方法。该方法首先预测报文丢失数量和纠错报文传输时延,从而选择合适的纠错编码模式,并为纠错编码分配比特数。实验结果表明该方法有效降低无线信道下报文丢失率,显著提高了图像质量。     

基于CDMA 1X的无线视频传输系统

设计并实现了基于CDMA 1X的无线视频传输系统,详细论述了传输模块中PPP连接、RTP封装和Socket通信的设计过程.并针对CDMA 1X信道的特点.进行了视频差错控制技术方面的研究,在平衡图像质量和编码比特率这对矛盾方面获得了良好的效果.     

基于抽取和内插方法的无线视频传输系统研究

为解决无线视频传输带宽较窄且不稳定的缺点,在编解码时转换视频分辨率印编码时抽取、解码时内插来降低传输的码率,并在抽取前进行预滤波以减少混叠,同时对视频的码率进行有效的控制,从而保证了较好的图像质量.     

视频传输中的差错控制和隐藏技术

本文介绍了视频传输中差错控制和隐藏的多种方法，着重阐述了怎样利用视频数据的相关性来恢复传输错误的数据以及如何限制错误码元的扩散，随后介绍了在MPEG-4中采用的一些差错控制和隐藏方法与H.264中采用或可能采用的一些错误恢复技术。     

基于丢包率统计的无线流媒体码率动态适配技术的研究

随着移动通信技术的不断发展,流媒体视频在无线环境下的应用得到普及。然而,移动网络环境所存在的不稳定性可能导致误码率高以及阻塞丢失严重的情况,从而严重影响用户的观看体验。因此,如何在现有移动网络环境发生频繁切换或网络较不稳定的情况下,仍使用户获得较好的流媒体视频播放体验,成了迫切需要解决的课题。本文研究提出了一种基于丢包率统计的无线环境下流媒体码率动态适配的方法,能够根据网络环境条件为用户重新选择适合用户的播放体验的视频码率,从而保证视频的传输质量和流畅度,优化用户的视频体验。     

无线多跳混合路由视频传输

提出了一种同时利用机会路由和传统路由进行跨层优化的实时视频传输方法,通过将I帧和P帧分别利用不同路由进行传输,获得了比单独利用传统路由或机会路由更好的性能。     

无线自组织网传输功率控制与跨层优化

无线自组织网节点功率有限，如何有效利用节点电量、改善网络性能是自组网领域研究的关键问题。首先讨论了节点传输功率对各协议层的影响，并归纳出功率控制的设计原则；然后分类介绍和比较了几种主要的控制机制。在传统协议分层研究的基础上，提出了对传输功率控制进行跨层优化的设计思想，并对运用跨层优化的困难给予了阐述；最后给出了传输功率控制领域最新的一些研究方向。     

视频编码新技术12题第二讲视频传输的差错控制

本文首先介绍了视频传输中三种常用的差错控制技术;然后着重介绍了其中的可分级编码技 术,包括时间、空间、信噪比、精细可分级技术;最后介绍了多描述编码和信源信道联合编码技术。     

3D视频的错误隐藏快速算法

具有独特编码结构的3D视频在不可靠信道上传输时遭遇丢包后极易造成错误传播,因此研究基于3D视频的错误隐藏技术十分必要.而且,压缩后传输的3D视频数据量仍然较大,这对解码器的解码速度提出了很高的要求.如何在解码端加速进行错误隐藏是研究重点,通过快速定位静止宏块的方法加速错误隐藏速度.实验结果表明该算法在保证不降低视频的主、客观质量的同时,能有效地降低错误隐藏算法的复杂度.     

视频流关键技术的研究进展

视频流是在因特网上进行视频信息传送的主流方式.为了在因特网上传输高质量的视频流,需要采取相应的传输机制.本文从视频流传输框架出发,系统讨论了当前视频流关键技术的研究进展,分析了各种技术的特点,并指出进一步发展的前景.     

基于Internet的实时视频流的应用层QoS控制策略

分析了Internet上实时视频传输的特点，提出了基于Internet的实时视频流的应用层QoS控制策略，主要包括拥塞控制策略和差错控制策略以及相应的控制技术。在拥塞控制中，讨论速率控制和速率整形，速率控制主要是根据网络运行状态预测当前可用的带宽，并根据预测值调整视频速率，达到与可用带宽匹配；速率整形则是迫使发送端以码率控制算法规定的码率发送视频流。在差错控制中，则讨论了编码器差错复原、解码器错误隐藏和编码器／解码器交互的差错控制等控制策略。这些控制技术应用于终端系统并不需要路由器和网络的QoS支持，可以最大限度地提高视频质量。     

一种基于HTTP长连接的自适应流媒体传输系统

提出了一种基于HTTP的自适应流媒体传输系统,一方面,该系统利用了HTTP长连接技术,有效地减少了频繁建立与断开TCP连接带来的网络资源开销;另一方面,该系统采用了一种服务器端驱动的码率自适应控制策略,这种策略不仅有效地适应于网络环境的变化,还降低了对客户端的要求,具有很强的通用性。实验结果表明该系统方案是有效的。     

3D visual experience oriented cross-layer optimized scalable texture plus depth based 3D video streaming over wireless networks

3D video streaming over the mobile Internet generally incurs the inferior 3D visual experience due to the time-varying characteristics of wireless channel. The conventional video streaming optimization methods generally neglect the harmony among different networking protocol layers. This paper proposes a cross-layer optimized texture plus depth based scalable 3D video streaming method to improve the expected 3D visual experience of the user by systematically considering the application layer texture-video/depth/FEC bit-rate allocation, MAC layer multi-channel allocation, and physical layer modulation and channel coding scheme (MCS) selection. In the cross-layer optimization, a networking-related 3D visual experience model which fuses the overlapped retinal view visual quality and depth sensation with mimicking human vision system is established to predict the 3D visual experience under the specific parameter configurations of different protocol layers. The efficiency and effectiveness of the proposed cross-layer optimized 3D video streaming method has been validated by subjective and objective experimental results.     

A Video Streaming System for Mobile Phones: Practice and Experience

This paper presents a case of video streaming system for mobile phone which has actually been implemented and deployed for commercial services in CDMA2000 1X cellular phone networks. As the computing environment and the network connection of cellular phones are significantly different from the wired desktop environment, the traditional desktop streaming method is not applicable. Therefore, a new architecture is required to suit the successfully streaming in the mobile phone environment. We have developed a very lightweight video player for use in mobile phone and the related authoring tool for the player. The streaming server has carefully been designed to provide high efficiency, reliability and scalability. Based on a specifically-designed suite of streaming protocol, the server employs an adaptive rate control mechanism which transmits the media packets appropriately into the network according to the change in network bandwidth.Hojung Cha is currently a professor in computer science at Yonsei University, Seoul, Korea. His research interests include multimedia computing system, multimedia communication networks, wireless and mobile communication systems and embedded system software. He received his B.S. and M.S. in computer engineering from Seoul National University, Korea, in 1985 and 1987, respectively. He received his Ph.D. in computer science from the University of Manchester, England, in 1991.Jongmin Lee is a Ph.D. candidiate in computer science at Yonsei University, Seoul, Korea. His research interests include wireless multimedia system, QoS architecture, multimedia communication networks. He received his B.S. and M.S. in computer science from Kwangwoon University in 1999 and 2001, respectively.Jongho Nang is a professor in the Department of Computer Science at Sogang University. He received his B.S. degree from Sogang University, Korea, in 1986 and M.S. and Ph.D. degree from KAIST, in 1988 and in 1992, respectively. His research interests are in the field of multimedia systems, digital video library, and Internet technologies. He is a member of KISS, ACM, and IEEE.Sung-Yong Park is an associate professor in the Department of Computer Science at Sogang University, Seoul, Korea. He received his B.S. degree in computer science from Sogang University, and both the M.S. and Ph.D. degrees in computer science from Syracuse University. From 1987 to 1992, he worked for LG Electronics, Korea, as a research engineer. From 1998 to 1999, he was a research scientist at Telcordia Technologies (formerly Bellcore) where he developed network management software for optical switches. His research interests include high performance distributed computing and systems, operating systems, and multimedia.Jin-Hwan Jeong received the B.S. and M.S. degrees in computer science from Korea University, Seoul, Korea, in 1997, and 1999, respectively. He is currently in Ph.D. course at Korea University. His research interests include video processing for thin devices, multimedia streaming and operating systems.Chuck Yoo received the B.S. degree in electronics engineering from Seoul National University, Seoul, Korea and the M.S. and Ph.D. in computer science in University of Michigan. He worked as a researcher in Sun Microsystems Lab. from 1990 to 1995. He joined the Computer Science and Enginnering Department, Korea University, Seoul, Korea in 1995, where he is currently a professor. His research interests include high performance network, multimedia streaming, and operating systems.Jin-Young Choi received the B.S. degree from Seoul National University, Seoul, Korea, in 1982, the M.S. degree from Drexel University in 1986, and the Ph.D. degree from University of Pennsylvania, in 1993. He is currently a professor of Computer Science and Engineering Department, Korea University, Seoul, Korea. His current research interests are in real-time computing, formal methods, programming languages, process algebras, security, software engineering, and protocol engineering.