共查询到19条相似文献,搜索用时 187 毫秒
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MPEG-2传送流传输方法的研究与改进 总被引:5,自引:0,他引:5
高品质视频流媒体的传输在流媒体业务中占有很重要的地位,同时带来许多难题.以传统的恒定速率传输变比特率压缩的视频时,播放终端往往需要很大的缓存.PCR协助的恒定速率传输是一种新的恒定速率传输机制.这个方法的详细研究表明PCBR方法利用嵌入MPEG-2传送流的程序参考时钟来定期校正传送速率,是以较高传输速率为代价减少了缓存需求.因此对该方法进行了改进,通过缩小传输时间尺度来降低传送速率但没有增加额外的缓存需求,在NS通信系统仿真软件和实验平台的测试结果都表明,改进的方法能够更好服务于流媒体传输与终端回放. 相似文献
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随着互联网的日益发展,人们对流媒体的需求不断提高,对视频服务器提出了更高的要求。P2P视频点播系统中传统的缓存替换策略无法获得很好的用户体验。针对此问题,本文对传统的缓存算法FIFO进行改进,提出基于关联规则的FIFO替换算法(FIFO-AR)。为了进一步提升缓存替换算法的性能,提出一种新的基于关联规则的缓存替换算法(CRA-AR)。根据用户的播放记录和视频段的流行度,并结合关联规则,从而得到待缓存的视频段。实验结果表明,FIFO-AR和CRA-AR相比于传统的缓存替换算法,具有较高的命中率和较少的响应时间。 相似文献
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针对APON提出了一种媒体接入控制(MAC)协议。该协议的设计遵照ITU—T有关APON的G.983定义的帧结构。该协议能支持CBR、VBR、ABR和UBR等多种业务.并能保证用户公平地接入和充分利用网络资源。其中CBR/VBR业务的优先级较高.同时也确保ABR业务至少能以最小信元速率通信,系统的剩余带宽被分配给UBR业务。最后,给出了硬件实现框图。 相似文献
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随着新一代视频编码标准AVS的发展,如何在IP网上实时传输AVS视频流对于IPTV,对于视频点播系统的应用有重要意义.利用RTP/RTCP协议设计并实现了一种基于AVS编码标准的实时视频传输系统,通过应用排队论采设计接受端缓冲区并将接收端缓存区的状态信息反馈到发送端控制发送端的发送速率,从而减少由于接收端缓存溢出带来的数据包的丢失,提高传输的QoS质量. 相似文献
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随着计算机技术和高速网络技术的发展,视频点播系统已变成现实,并且具有巨大的潜在需求。利用视频对象简介能够给用户一个友好的互动收视环境。可扩展视频服务器集群可以适应未来的用户需求的快速增长。视频对象分段技术和前缀缓存技术使视频文件按照一定的缓存策略以分段方式分布在协作式的缓存服务器集群中,以利于服务器集群的负载平衡和减少对用户的启动延迟。系统还引入了IP组播技术来减少对网络带宽的开销。该文提出了混合式的协作缓存和IP组播的方式交付视频对象,并描述了它是如何工作的。 相似文献
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提出了一种在分层视频组播应用中,组播源能根据组播应用类型选择最优层速率的方法,目的是提高组播组的全局视频质量。考虑到组播应用类型的不同,该文给出了一个全局质量因子(GQI),反映了接收端的满意程度(接收端总的视频质量下降程度),组播组占用的网络带宽和接收端视频质量的稳定性。这些指标可根据组播应用类型的不同进行调整。仿真验证,在使用GQI作为衡量组播组全局视频质量的标准时,能够保证所要优化的目标,达到用户的需求。 相似文献
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针对实时VBR视频流式传输的在线平滑优化问题,提出一种基于漏斗的最短路径平滑算法——SPSF。SPSF利用滑动窗口对实时VBR视频进行分段处理,顺序读取和缓存每帧视频数据至窗口,并基于漏斗原理求解窗口内数据的最短路径。数据填满窗口后根据求得的最短路径进行传输,同时根据路径特征推进窗口滑动进行下一段数据的平滑处理及传输,以此类推完成整个视频平滑传输。实验结果表明,与传统的在线平滑算法相比,SPSF具有更优的传输比特率峰值、传输比特率谷值、及传输比特率方差;与传统的最短路径算法相比,SPSF具有更快的最短路径 相似文献
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文中介绍了异步传输模式中的四种业务模型:恒定比特率业务模型CBR、实时可变比特率业务模型rt—VBR和非实时可变比特率业务模型nrt—VBR、可用比特率业务模型ABR,其中详细分析并讨论了非实时的可变比特率和可用比特率两种业务模型,通过对这两种模型进行性能评价以阐明其基本特点。 相似文献
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In this paper we discuss the source rate control problem of adapting variable bit-rate (VBR) compressed video over constant bit-rate (CBR) channels. Firstly we formulate it as an optimal control problem of a discrete linear system with state and control constraints. Then we apply the discrete maximum principle to get the optimal solution. Experimental results are given in the end. Compared with traditional algorithms, the proposed algorithm is suitable for the coder with continuous output rates, and can achieve the better solution. Our algorithm can be used in both off-line and on-line coding. 相似文献
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In this paper we discuss the source rate control problem of adapting variable bit-rate (VBR) compressed video over constant bit-rate (CBR) channels. Firstly we formulate it as an optimal control problem of a discrete linear system with state and control constraints. Then we apply the discrete maximum principle to get the optimal solution. Experimental results are given in the end. Compared with traditional algorithms, the proposed algorithm is suitable for the coder with continuous output rates, and can achieve the better solution. Our algorithm can be used in both off-line and on-line coding. 相似文献
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A joint rate control algorithm for variable bit rate (VBR) MPEG-compressed digital video on point-to-point permanent virtual
circuit (PVC) ATM links is proposed. The algorithm controls the encoding mode of a number of video encoders that operate either
on VBR or constant bit rate (CBR) mode. The algorithm selects the encoding mode based on the buffer occupancy of a multiplexer
co-located with the encoders that interfaces them to the PVC link. VBR encoding is the predominant encoding mode used during
congestion-free periods. CBR mode is used only during congested periods. When CBR is selected, new bit rates are jointly assigned
to the encoders based on their relative encoding complexities. The bit rate assigned to the encoders are enforced by a CBR
rate control local to each encoder. The performance of the joint rate control algorithm is evaluated through simulation of
a packet multiplexer, where a number of connections are multiplexed onto a fixed-capacity channel. The performance is compared
to that of multiplexing conventional CBR and open-loop VBR from the video quality and bandwidth efficiency points of view.
Simulation results show that the proposed algorithm improves performance over multiplexed conventional CBR or open-loop VBR
MPEG video, without significantly increasing implementation complexity. The application of the algorithm to video-on-demand
over ATM is discussed. 相似文献
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本文讨论了可变比特率(VBR)视频流在有服务质量(QoS)保证的信道上传输时的信源和信道速率控制问题.首先将其表述为离散线性时延系统的最优控制问题,然后利用离散极大值原理得到该问题的最优解.和传统的解决方案相比较,本文的方法适合于具有连续输出码率的编码器,并对于编码器和解码器的缓冲区大小没有特殊要求,理论分析和实验结果表明,本文的方法具有更低的复杂度.该方法既能用于离线编码,也能用于在线编码. 相似文献
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This paper is concerned with transmission of Moving Picture Expert Group (MPEG) video over a Bluetooth wireless network using a fuzzy approach. MPEG Variable Bit Rate (VBR) video sources suffer from long delay and excessive loss due to the sudden bursts in bit rate. Constant Bit Rate (CBR) encoding scheme may work well for a network with a guaranteed bandwidth. However, a Bluetooth channel is subject to wireless interference and can never guarantee a constant bandwidth. Subsequently, it is impossible to transmit a CBR video over Bluetooth wireless without data loss or image quality degradation. To resolve this problem, a fuzzy control system is introduced at the Host Controller Interface (HCI). The system consists of a traffic-shaping buffer whose role is to prevent excessive back-to-back cells being generated during the peak transmissions of MPEG video sources. The output bit rate of the traffic-shaping buffer is controlled by a fuzzy controller to ensure that the video stream from the host conforms to the traffic condition of the Bluetooth channel. Another fuzzy controller regulates the average arrival bit rate to the traffic-shaper to guarantee that the buffer is neither full nor empty. Computer simulation results demonstrate that the use of the fuzzy controllers reduces excessive data loss at the HCI as compared with an open loop VBR/CBR video transmission in Bluetooth. 相似文献
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针对实时VBR视频流式传输的在线平滑优化问题,提出一种基于漏斗的最短路径平滑算法——SPSF。SPSF利用滑动窗口对实时VBR视频进行分段处理,顺序读取和缓存每帧视频数据至窗口,并基于漏斗原理求解窗口内数据的最短路径。数据填满窗口后根据求得的最短路径进行传输,同时根据路径特征推进窗口滑动进行下一段数据的平滑处理及传输,以此类推完成整个视频平滑传输。实验结果表明。与传统的在线平滑算法相比,SPSF具有更优的传输比特率峰值、传输比特率谷值、及传输比特率方差;与传统的最短路径算法相比,SPSF具有更快的最短路径求解速度,提高了视频传输的实时性。 相似文献
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在建立的区分服务网络模型的基础上,提出一种针对实时变比特率突发业务的调度算法,称为加权开关赤字轮循(weighted switch deficit round robin,WSDRR)算法.根据不同的队列等级分配加权的带宽,并根据队列中分组状况动态调节服务量.该策略是针对网络拥塞下传输实时突发视频业务而提出的.基于一种吞吐量公平测度的比较,WSDRR算法与传统赤字轮循DRR算法具备相同的公平性.实验结果表明,与DRR算法相比,WSDRR算法能够降低实时突发视频业务的端对端延时和延时抖动,从而进一步使实时视频传输的要求得到满足. 相似文献
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We consider streaming of video sequences over both constant and variable bit-rate (VBR) channels. Our goal is to enable decoding of each video unit before exceeding its displaying deadline and, hence, to guarantee successful sequence presentation even if the media rate does not match the channel rate. In this work, we show that the separation between a delay jitter buffer and a decoder buffer is in general suboptimal for VBR video transmitted over VBR channels. We specify the minimum initial delay and the minimum required buffer for a given video stream and a deterministic VBR channel. In addition, we provide some probabilistic statements in case that we observe a random behavior of the channel bit rate. A specific example tailored to wireless video streaming is discussed in greater detail and bounds are derived which allow guaranteeing a certain quality-of-service even for random VBR channels in a wireless environment. Simulation results validate the findings. 相似文献