共查询到20条相似文献，搜索用时 718 毫秒
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江玉珍 《韩山师范学院学报》2007,28(6):27-32
多描述编码(MDC)能有效提高数据在不可靠网络传输中的接收质量。结合JPEG编码原理,根据分块DCT系数的不同划分提出了两种图像MDC方法。该两种方法具有不同的应用特点,无论是单个描述还是两个描述的重构图均取得令人满意的效果。 相似文献
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不同的多视点视频序列具有不同的时空相关性,MVC采用的分层B帧预测结构无法充分利用视频序列的属性。本文提出了一种能适应不同视频序列编码的方法,通过研究多视点视频图像中的时空相关性和视点间的相关性,适当地取消部分时间层的视点间预测并且对所有P视点的非关键帧均采用视点间预测和调整了I视点的位置。实验结果表明,本文方法在提高编码效率的同时使得预测结构具有更好的随机访问性能、更低的编码复杂度。 相似文献
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在Ad hoc网络中入侵检测问题已经成为研究热点,本文首先对存在的安全隐患进行了分析描述,然后从会话过滤的角度出发,结合Ad hoc网络自身特点的基础上,提出了一种基于状态检测的入侵防护策略,用于提高整个网络的安全性. 相似文献
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许芷岩 《湖北第二师范学院学报》2011,(2):52-54
在Ad hoc网络中安全问题已经成为研究热点,本文首先对存在的安全隐患进行了分析描述,然后从节点间认证及密钥协商的角度,结合Ad hoc网络自身特点的基础上,提出了一种基于分簇的密钥认证安全策略,用于保证整个网络的安全性,提高了网络性能。 相似文献
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在Ad hoc网络中密钥的安全问题已经成为研究热点,本文首先对存在的安全隐患进行了分析描述,然后从节点间信任角度出发,结合Ad hoc网络自身特点,提出了一种带DoS入侵阻断功能的分布式密钥管理策略,用于保证整个网络的安全性,提高了网络性能。 相似文献
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Ad hoc网络--一种特殊的无线移动网络,其无中心、自组织、多跳路由以及动态变化的网络拓扑等特性,都使得Ad hoc网络在西部开展网络远程教育教学显示出极大的优越性.但通过对Ad hoc网络的研究和分析,发现它还存在许多问题:Ad hoc网络的平面和分级两种结构存在着可扩充性差,网络规模受限及簇头结点可能会成为网络瓶颈等缺憾;它的三种路由协议也面临着族的选择和维护以及节点的功耗等问题;还由于Ad hoc网络的物理条件所限,在实际应用中也必然会出现安全性能较差、电源采用电池供电时间受限以及在带宽、时延、时延抖动等方面都还难以达到较高的服务质量保证等诸多弊端. 相似文献
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贺学剑 《洛阳工业高等专科学校学报》2008,18(2)
在多媒体信息中,视频信息是一种比较特殊的媒体,数据量大,信息丰富.视频数据的表达、组织、存储和传输都有很大难度.帧间预测编码可以用来消除视频序列中大量的时间和空闻冗余,由此压缩视频序列.运动估计耗用整个编码器编码时间80%左右,成为最耗时的部分.本文分析视频压缩的基本原理,论述运动估计的哪特点,重点是视频编码中的运动估计算法研究以及比较各种运动估计算法的优劣. 相似文献
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王新风 《武汉职业技术学院学报》2008,7(1):94-95,104
提出了Ad hoc利用传统算法路由的缺限,讨论了Ad hoc网络中路由协议的独特需求,并归纳了当前Ad hoc网络中路由的问题。 相似文献
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提出一种基于3D-SPIHT视频多描述编码方案。与传统多描述编码例如MDSQ相比,该方案创建的各描述质量平衡,并能通过去除视频帧间冗余来提高压缩比;与国际标准(H.264等)相比,该编码方案具有算法简单、能够在任意码流截断处解码、码率可连续分级和无明显块效应等优点。实验表明该编码方案能够较好的应用于ZigBee多信道网络,并在较大压缩比的情况下仍能获取质量较好的重建图像,具有较高的应用价值。 相似文献
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INTRODUCTION In typical video transmission systems, a video signal is compressed, and the resulting bit stream is transmitted over an error-prone channel. The errors may consist of symbol errors caused by fading, as observed for wireless channels, or packet erasures caused by congestion, as observed in the Internet. If a received video packet contains errors, then the portion of the video signal contained in the packet is lost and must be concealed. Error concealment schemes alone cannot … 相似文献
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Although H.264 video coding standard provides several error resilience tools, the damage caused by error propagation may still be tremendous. This work is aimed at developing a robust and standard-compliant error resilient coding scheme for H.264 and uses techniques of mode decision, data hiding, and error concealment to reduce the damage from error propagation. This paper proposes a system with two error resilience techniques that can improve the robustness of H.264 in noisy channels. The first technique is Nearest Neighbor motion compensated Error Concealment (NNEC) that chooses the nearest neighbors in the reference frames for error concealment. The second technique is Distortion Estimated Mode Decision (DEMD) that selects an optimal mode based on stochastically distorted frames. Observed simulation results showed that the rate-distortion performances of the proposed algorithms are better than those of the compared algorithms. 相似文献
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The emergence of third generation mobile system (3G) makes video transmission in wireless environment possible, and the latest 3GPP/3GPP2 standards require 3G terminals support H.264/AVC. Due to high packet loss rate in wireless environment, error resilience for 3G terminals is necessary. Moreover, because of the hardware restrictions, 3G mobile terminals support only part of H.264/AVC error resilience tool. This paper analyzes various error resilience tools and their functions, and presents 2 error resilience strategies for 3G mobile streaming video services and mobile conversational services. Performances of the proposed error resilience strategies were tested using off-line common test conditions. Experiments showed that the proposed error resilience strategies can yield reasonably satisfactory results. 相似文献
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图像压缩技术是基于在空域,时域或者频域上移除数据冗余的算法。它相当大地减少了数据转换率,但是随之的视频压缩信号对于传输误差更加敏感。差错恢复技术相对于通道误差增强了视频比特流的鲁棒性。在H.264/AVC的条带编码作为一种差错恢复技术之一被用于限制接收视频品质的数据丢失效应。有一种模式非常重要,它是将图像的宏块分配成不同的条带组,并能够提供不同的差错恢复标准。该文将深入分析这一类分散类型的灵活的宏块顺序(FMO)模式性能,并提出一个定义明确的系统模式,可以更完全地挖掘宏块顺序中离差概念从而克服误差损失。仿真结果显示:新的改进方案的性能优于传统模式。 相似文献
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Error-resilient video communication over lossy packet networks is often designed and operated based on models for the effect of losses on the reconstructed video quality. This paper analyzes the channel distortion for video over lossy packet networks and proposes a new model that, compared to previous models, more accurately estimates the expected mean-squared error distortion for different packet loss patterns by accounting for inter-frame error propagation and the correlation between error frames. The accuracy of the proposed model is validated with JVT/H.264 encoded standard test sequences and previous frame concealment, where the proposed model provides an obvious accuracy gain over previous models. 相似文献
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一种新的无线视频传输帧内刷新策略 总被引：1，自引：0，他引：1
首先分析了无线信道突发性出错和二阶Markov无线信道模型. 根据该模型和视频编码器的编码方式推导了突发性出错引起的帧内编码和帧间编码的信道失真. 然后提出了一种新的速率失真率(R-D)框架内的帧内刷新策略. 该策略一方面对无线视频传输系统的容错性能和编码效率进行了优化, 另一方面可有效阻止帧间错误传播, 减小信道失真. 在不同传输信道中的仿真结果验证了该策略在无线视频传输容错方面的性能改进. 相似文献
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Error-resilient video communication over lossy packet networks is often designed and operated based on models for the effect of losses on the reconstructed video quality. This paper analyzes the channel distortion for video over lossy packet networks and proposes a new model that, compared to previous models, more accurately estimates the expected mean-squared error distortion for different packet loss patterns by accounting for inter-frame error propagation and the correlation between error frames. The accuracy of the proposed model is validated with JVT/H.264 encoded standard test sequences and previous frame concealment, where the proposed model provides an obvious accuracy gain over previous models. 相似文献
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Randall G. Rogan 《Communication quarterly》2013,61(2):157-173
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Asymmetric stereoscopic video coding can take advantage of binocular suppression in human vision by representing one of the two views in lower quality.This paper proposes a bit allocation strategy for asymmetric stereoscopic video coding.In order to improve the accuracy of bit allocation and rate control in the left view,a proportionalintegral-derivative controller is adopted.Meanwhile,to control the quality fluctuation between consecutive frames of the left view,a quality controller is adopted.Besides,a fuzzy controller is proposed to control the variation in quality between the left and right views by comparing the PSNR disparity of two views with a fixed threshold,which is used to quantize the binocular psycho-visual redundancy and adjust the quantization parameter (QP) of the right view correspondingly.The proposed algorithm has been implemented in H.264/AVC video codec,and the experimental results show its effectiveness in rate control while keeping a good quality for the left view,and fewer bits are allocated for the right view so that the overall bit rate is saved by 7.2% at most without the loss of subjective visual quality for stereoscopic video. 相似文献