共查询到19条相似文献，搜索用时 203 毫秒
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借鉴TFRC拥塞控制模型原理,提出一种网络拥塞自适应解决策略,按照该网络拥塞解决策略的要求,结合网络视频流传输相关技术为系统后台服务端设计了一个网络拥塞处理模块。该模块通过接收端反馈回来的网络状况报告,制定出平滑的数据传输带宽,系统根据该传输带宽对数据发送模块和视频编码模块运作进行指导。 相似文献
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靳勇 《常熟理工学院学报》2010,24(2):87-94
提出一种用于无线实时流媒体传输的数据链路层自适应SR-ARQ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,基于增强型GM(1,1)模型预测当前的网络状态,自适应地调整SR-ARQ参数N_(max)(最大重传次数),同时依据逻辑链路控制子层(LLC layer)不同的操作类型为MPEG三种视频帧(I,P和B帧)提供不同优先级的服务;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.数学分析与仿真实验的统计结果对比表明,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. 相似文献
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在网络环境下的远程视频教学过程中,首先要保证的是视频传输的实时性,而网络状况直接决定了服务质量的好坏。本文构建了视频传输模型并通过实验表明,以丢包率为依据调整视频压缩质量和采集速率来适应变化中的网络带宽,从而保证视频传输的实时性是可行的。 相似文献
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视频信息在网络远程教学中的应用已经越来越广泛,但其传播效果却并不令人满意。分析了影响网络视频传播效果的主要因素,研究了视频编码方式与运行环境的关系,并通过实际的网络测试,提出了根据视频长短、使用环境来决定视频的编码方式和编码比特率的解决方案,从而使各种视频在网络上传输达到最佳效果。 相似文献
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陈颖 《福建信息技术教育》2007,(4)
以H.264/AVC为代表的新一代视频编码技术,采用分层模式,不仅通过视频编码层改善了编码效率,而且通过网络提取层提高了网络传输适应性,并且在封装规范中体现了流媒体实时传输特性。 相似文献
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为增强无线多跳网络（Ad hoc网络）中视频传输的抗误码性能,提出了一种面向Ad hoc网络的视频多描述编码及其传输方法。首先,通过判断两个相邻帧运动矢量的差值,自适应地在视频序列中插入参考帧以提高帧间编码效率;然后分别抽取出视频序列中的奇数帧和偶数帧形成两个描述;最后,在确保传输路径可靠性的基础上,选取两个质量较高的节点不相交路径分别传输视频序列的两个描述,以提高视频传输的可靠性。OPNET Modeler中的仿真实验结果表明,与目前Ad hoc网络中典型的多描述编码及传输方法MDC_AODV相比,本文提出的方法有效地增强了视频传输的抗误码性,提高了接收端的视频质量。 相似文献
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结合空时OFDM和转换编码技术,提出了一种无线衰落信道下具有可分级转码能力的鲁棒视频传输方法.采用可分级转码器将高质量的MPEG-2压缩视频转换为低码率、低分辨率MPEG-4可分级码流来满足网络带宽和终端设备显示的要求.在接收端采用一种层干扰抑制算法,使得分层空时OFDM系统不同层的传输性能存在差异,从而使系统具有不对等保护能力.根据分级码流的重要程度不同,将转码输出的可分级码流分别由分层空时编码OFDM系统的不同层来实现视频的鲁棒传输.实验结果表明:在典型的随机突发错误的无线环境下,提出的具有可分级转码能力的系统的视频传输性能优于传统的非分级转码的视频传输系统. 相似文献
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在网络上实时传输视频流,必须采取防止拥塞的措施,才能保证其服务质量.通过调整码流量来匹配网络带宽的变化,通常采用实时传输协议RTP,利用RTP协议的反馈信息来估计网络状态,然后根据评估的网络状态,调整发送端的传输率,以此实现自适应网络传输. 相似文献
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孙伟 《现代远程教育研究》2011,(3):84-88
随着互联网应用技术的发展与网络带宽的提升,网络学习已逐渐趋向动态影音内容提供、实时影音互动及后台数据传输等服务的整合时代。将流媒体技术、视频媒体服务器、Adobe＆Macromedia Flash网页应用程序、XML与ASP.NET等多项技术进行综合探讨及应用,建构一个多人多方的集实时视频教学、视频点播、资料存取与学习评价于一体的RIA网络学习平台,可实现跨操作系统存取各类信息,强化教学内容所呈现的视觉效果,提升学习者主动学习意愿,最终达到提升网络教学的效果。 相似文献
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An adaptive load balancing scheme is proposed to balance the load in ad hoc networks. The new scheme can be applied in most on-demand routing protocols resulting in significant performance improvement. The proposed scheme is applied to the ad hoc on-demand distance vector (AODV) routing protocol. Simulation results show that the network load is balanced on the whole, and performance in packet loss rate, routing overhead and average end-to-end delay is also improved. 相似文献
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应用跨层设计的思想,提出了一种结合网络层和MAC层的跨层带宽预留保证机制——邻居预留（NR,Neighborhood Reservation）,以减轻Ad Hoc网络中由于相邻节点在MAC层的信道竞争,对带宽预留产生的影响。 相似文献
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JI Xin POLLIN Sofie LENOIR Gregory LAFRUIT Gauthier DEJONGHE Antoine CATTHOOR Francky 《浙江大学学报(A卷英文版)》2006,7(Z1)
This paper introduces a video application-aware cross-layer framework for joint performance-energy optimization, considering the scenario of multiple users upstreaming real-time Motion JPEG2000 video streams to the access point of a WiFi wireless local area network and extends the PHY-MAC run-time cross-layer scheduling strategy that we introduced in (Mang-haram et al., 2005; Pollin el al., 2005) to also consider congested network situations where video packets have to be dropped. We show that an optimal solution at PHY-MAC level can be highly suboptimal at application level, and then show that making the cross-layer framework application-aware through a prioritized dropping policy capitalizing on the inherent scalability of Motion JPEG2000 video streams leads to drastic average video quality improvements and inter-user quality variation reductions of as much as 10 dB PSNR, without affecting the overall energy consumption requirements. 相似文献
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针对3G/ad hoc融合网络提出了一种性能分析方法.接收功率与路径的衰减关系基于路径的自然损耗与阴影衰落.首先,对3G/ad hoc融合网络的应用场景模型进行了简要的介绍.然后,基于此网络的应用场景,提出了几种性能分析方法来计算融合网络的中断概率、掉话率、新呼叫用户拥塞率等性能指标,随后推导出相应的性能公式并与传统3... 相似文献
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Dave Hearnshaw 《British journal of educational technology : journal of the Council for Educational Technology》2000,31(3):221-228
Desktop Videoconferencing (DVC) has been shown to support effectively remote tutorials, but specific video channel requirements are not known. There is a perception that higher levels of image quality will enhance the effectiveness of the tutorial, and this has implications on scarce network bandwidth. If it can be shown that low levels of image quality are not detrimental to learning opportunities, then the use of DVC will be more attractive to institutions inhibited by fear of high network demands.
Limitations in current methods for assessing video channel quality are discussed, and a new scheme for tutorial content quality analysis is outlined. The scheme has been applied to data gathered from a trial involving 30 students studying for an accredited university module. The results show that increasing the quality of the video channel resulted in no measurable increase in the quality of dialogue within the tutorials. The conclusions are that low quality images are not necessarily detrimental, and therefore DVC could be endorsed more readily where bandwidth is limited. 相似文献
Limitations in current methods for assessing video channel quality are discussed, and a new scheme for tutorial content quality analysis is outlined. The scheme has been applied to data gathered from a trial involving 30 students studying for an accredited university module. The results show that increasing the quality of the video channel resulted in no measurable increase in the quality of dialogue within the tutorials. The conclusions are that low quality images are not necessarily detrimental, and therefore DVC could be endorsed more readily where bandwidth is limited. 相似文献
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Peer-to-peer （P2P） technology provides a cost-effective and scalable way to distribute video data. However, high heterogeneity of the P2P network, which rises not only from heterogeneous link capacity between peers but also from dynamic variation of available bandwidth, brings forward great challenge to video streaming. To attack this problem, an adaptive scheme based on rate-distortion optimization （RDO） is proposed in this paper. While low complexity RDO based frame dropping is exploited to shape bitrate into available bandwidth in peers, the streamed bitstream is dynamically switched among multiple available versions in an RDO way by the streaming server. Simulation results show that the proposed scheme based on RDO achieves great gain in overall perceived quality over simple heuristic schemes. 相似文献
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移动自组网多路径路由具有有效使用带宽、均衡负载和增加传输可靠性等方面的优势。路由发现是路由协议的重要组成部分,分析了设计多路径路由协议的路由发现部分的关键问题及不同策略,对近几年国内外提出的多路径路由协议在路由发现部分进行了比较,指出了多路径路由发现中需要进一步研究的问题。 相似文献
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大规模ad hoc网络下的高效的主动RSA方案 总被引：1，自引：0，他引：1
A previous proactive RSA scheme for large-scale ad hoc network has been shown to be faulty. In this paper, we present a new proactive RSA scheme for ad hoc networks, which includes four protocols： the initial key distribution protocol, the share refreshing protocol, the share distribution protocol, and the signature generation protocol. This scheme has two advantages： the building blocks are secure, and the system is efficient. 相似文献
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为解决网络队列动态预测问题,提出一个网络系统在泊松分布流量和指数服务时间下的暂态队列行为预测模型并进行仿真验证。阐述基于扩展卡尔曼滤波（Kalman）的预测模型及其具体算法,结合网络中的数据流量特性,构建基于扩展卡尔曼滤波器的网络暂态队列预测模型,并根据仿真网络中的实际数据对模型进行验证。实验结果表明,所建立的网络暂态队列实时预测模型预测效果比较理想,基本与实时队列长度保持一致。因此,该模型可以较低的代价应用于网络中的动态路由算法及拥塞控制算法中。 相似文献