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VBR流式视频的最短路径率平滑传输算法 总被引:6,自引:0,他引:6
预存储的变比特率(VBR)压缩的视频网上流式传输,提供实时视频服务.这种VBR视频呈现的突发性比特率变化特性使带宽预留和接纳控制等网络传输技术复杂化.一个行之有效的解决办法是在传输前对这种VBR视频在满足一定限制条件下进行比特率无损平滑.基于平面规划中的最短路径原理,针对存储的VBR压缩视频,文章提出了最短路径率平滑传输算法,并建立了一些相关概念.算法的结果被证明能同时满足多项优化指标:极小的峰值比特率、极大的谷值比特率及O(K)的时间复杂性,实验结果也显示算法是有效、可行的. 相似文献
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基于预取的流视频带宽适应性传输算法 总被引:1,自引:0,他引:1
谢建国 《计算机研究与发展》2009,46(2)
IP网络带宽的动态特性是流视频要面临的关键问题.可伸缩编码的视频具有带宽适应性,但由于其每一层编码通常是变比特率的,那么在视频传输中,为迎合动态传输带宽,如何裁减这种分层的变比特率视频,并极大化一定的目标性能,需要传输优化.针对上述问题,提出了一个预取或缓冲优化的流视频带宽适应性传输框架,将裁减策略放到一个窗口来考虑,解决了窗口内的最小裁减量问题,其带宽适应性粒度在理论上可以细化到"比特位",并为其他裁减算法提供综合优化的计算平台. 相似文献
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基于MPEG-4的视频流传输框架 总被引:3,自引:0,他引:3
视频的实时传输存在带宽、传输延迟、包丢失率等方面的要求,而当前的Internet环境下未提供任何QoS(服务质量)服务,所以一个有效的视频传输系统必须自适应于网络状况的动态变化。在充分发掘MPEG-4特性的基础上,该文构造了一个基于MPEG-4的视频流传输框架。通过使用带宽预测、自适应速率调整、SFEC纠错、错误隐藏等机制使视频的传输能够自适应于网络状况的动态变化。同时,提出了一种基于优先级的速率调整算法,克服了传统基于R-D理论的速率调整算法对媒体源支持单一的缺点。试验结果表明,该系统在低比特率、网络状况动态变化的环境中能取得良好的视频传输效果。 相似文献
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《计算机应用与软件》2017,(8)
对基于HTTP协议的动态自适应流媒体来说,客户端可以根据不同的网络状况自适应地调整请求的视频比特率。当前DASH的研究主要集中于单链路的比特率切换算法的设计。而考虑到移动终端拥有多个网络接口以及短视频的播放流行度,开发一个基于LTE/Wi-Fi的多接口DASH系统——PASM(Predictive Adaptive Streaming system over LTE/Wi-Fi Multiple access networks)。PASM从两个互补方面提高了DASH性能,一方面,减少了由于两条链路异构性造成的视频块的乱序到达,充分利用两条链路的带宽之和进行DASH传输,提高了请求视频的质量;另一方面,在剩余请求视频时长不多时,采用一种更加激进的视频比特率请求算法,减少了带宽的不充分利用,提高了视频的平均比特率。实验结果表明,在各种链路带宽差异的网络下,PASM保证了视频比特率的平滑切换,同时提高了视频平均比特率。 相似文献
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码率控制是在低带宽信道上传输低延迟、高质量视频的关键技术之一.根据基于PSTN信道的远程视频监控应用需求,提出一种甚低码率控制策略,通过为视频编码器增加Ⅰ帧码率控制,改进P帧的位率控制算法,以及引入二阶率失真模型,较好地解决了甚低带宽下视频编码器的码率控制问题.实验结果表明,算法降低了编码缓冲区延迟同时提高了重建图像的质量。 相似文献
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区分服务网络基于测量的接纳控制方案的设计与应用 总被引:9,自引:0,他引:9
提出了一种分布式可扩展的接纳控制方案,其目的是为区分服务网络提供端到端服务质量(Quality of Services,QoS)保证,该方案主要由以下部分构成:(1)连接接纳控制协议,主要负责主机和网络节点以及网络节点和带宽代理之间的信息传送,实现对连接请求的串行操作;(2)位于网络核心节点的可用带宽估计算法;(3)位于网络边缘节点的接纳控制算法;给出了该方案在视频传输方面的应用实例;利用多种网络拓扑结构和QoS指标评价该方案的性能,实验结果表明该方案能准确地控制可接纳区域和提高网络资源的利用率。 相似文献
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为了保证用户的服务质量(QoS),宽带分组网络需要进行动态带宽分配,而视频流量预测在动态带宽分配中发挥着重要的作用。本文从自相关性、自相似性的Hurst参数两个方面,阐明图像组(GOP)时间尺度上的流量能够体现原有视频帧序列的流量特性,并在固定步长的LMS自适应算法(FSSA)的基础上提出了一种新的可变步长自适应算法(VSSA),在GOP所表示的大时间尺度上预测MPEG4视频流量。大量的仿真实验结果表明,VSSA算法可以明显地改善预测性能。 相似文献
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IEEE 802.15.3, an emerging wireless technology, was designed to provide high-quality multimedia services at home. Dynamic bandwidth allocation for a multimedia connection should be considered in order to achieve higher channel utilization, less buffer and less delay, especially for variable bit rate (VBR) multimedia connections. For real-time VBR videos, the bandwidth requirement should be predicted adaptively for effective channel-time requests. Previously, the adaptive least-mean square (LMS) algorithm with fixed step size was applied to predict channel time requirements due to its simplicity and relatively good performance. However, the performance might degrade when scene changes occurred. In this paper, we modify the variable step-size LMS algorithm and apply it as our predictor (VSSNLMS) so that the prediction errors on scene changes can be effectively reduced. Using the prediction results of VSSNLMS, we propose a dynamic bandwidth-allocation scheme that is scene-change aware and can guarantee the delay bound of real-time VBR videos. Simulation results show that the VSSNLMS predictor is superior to previous LMS-type predictors in performance, and the proposed scheme has better performance in channel utilization, buffer usage, and packet loss 相似文献
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相比于之前主流的H.264视频压缩编码标准,HEVC在保证重建视频质量相同的前提下,可以将码率降低近50%,节省了传输所需的带宽.即便如此,由于一些特定的网络带宽限制,为继续改善HEVC视频编码性能,进一步提升对视频的压缩效率仍然是当前研究的热点.本文提出一种HEVC标准编码与帧率变换方法相结合的新型的视频压缩编码算法,首先在编码端,提出一种自适应抽帧方法,降低原视频帧率,减少所需传输数据量,对低帧率视频进行编解码;在解码端,结合从HEVC传输码流中提取的运动信息以及针对HEVC编码特定的视频帧的分块模式信息等,对丢失帧运动信息进行估计;最后,通过本文提出的改进基于块覆盖双向运动补偿插帧方法对视频进行恢复重建.实验结果证实了本文所提算法的有效性. 相似文献
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为减少码率控制中实际输出码率与目标码率之间的误差,改善视频序列编码尾部质量下降的缺陷,同时针对可伸缩视频编码中码率控制算法的不足,提出一种自适应比特分配的码率控制算法。算法基于对根据相邻图像帧之间的相关性以及对恒定质量的考虑,在图像组(GOP)之间平均分配目标比特,而在GOP内部则根据编码复杂度自适应分配目标比特,同时适当调整初始量化参数(QP),再根据目标比特分别计算P帧、B帧的QP。对不同的视频序列进行了实验测试,其结果验证了算法的准确性和有效性。 相似文献
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Zhong Fan 《Computer Communications》2009,32(5):954-960
The new ECMA-368 MAC for UWB WPANs consists of two channel access methods: the distributed reservation protocol (DRP) and prioritized contention access (PCA). The exact method of medium access slot (MAS) allocation in DRP is not specified in the standard. The contribution of this paper is twofold. First, the paper describes a distributed resource allocation method in which a number of interference–avoidance rules are used to reserve slots for devices. Devices maintain sending and receiving tables to track activities in the neighbourhood. The proposed method is a simple, effective solution to the DRP MAS allocation problem, avoiding reservation conflicts and interference from hidden terminals. Secondly, for VBR MPEG-4 video traffic, we propose a bandwidth requirement calculation method based on traffic prediction. In the proposed scheme bandwidth is allocated based on accurate traffic predictions, therefore matching network resources to the traffic demand. Application QoS is maintained while network utilization is kept high. Furthermore, the simple, adaptive linear predictor does not incur much computation overhead. Simulation results have demonstrated the accuracy of the proposed prediction algorithm and effectiveness of the bandwidth allocation method. 相似文献
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The broadband integrated services digital networks (B-ISDN) based on asynchronous transfer mode (ATM) technology can support
a wide range of applications such as voice, video, still images, and data. Compression techniques increase the effective bandwidth
utilization, but the bursty and asynchronous nature of the traffic can still lead to congestion in the network, and degradation
of image quality and quality of service (QOS). Some of the features to provide better coding schemes for ATM networks are
layered coding, resynchronization, buffering, interleaved schemes, constrained bit rate due to buffers, encapsulation with
the RTP or AAL1 for clock recovery, lapped transforms, motion compensation, and optimal bit allocation for coders based on
wavelet transforms. We review various techniques forimage and video coding such as transforms, motion compensation, vector
quantization, and subband coding. We outline the impact of the cell loss ratio (CLR), delay and cell delay variation (CDV)
on video coding: blocking effects, loss of frame synchronization, motion vectors, and vector quantization codewords. The open
problems include tuning coding parameters to the available QOS provided by the network. 相似文献
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基于Matching Pursuits的误差图像编码算法因其基函数的灵活性,是一种在低码率视频编码应用中较为理想的算法,块能量搜索算法被用于减少该算法的编码复杂度,针对固定权值加权块搜索算法的不足之处,提出了一种自适应加权块搜索算法,在不增加算法复杂度的情况下,对不同的被编码序列采用不同的权值表完成加权块能量算法,在各种情况下均得到了较理想的编码效果。 相似文献
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《Real》1999,5(2):83-94
In this paper we present an adaptive frame type selection algorithm for motion compensation, which is applied to a low bit rate video coding using MPEG-1. In the adaptive scheme, the number of reference frames for motion compensation is determined by a scene change detection algorithm using temporal segmentation. To choose for the distance measure for the temporal segmentation, three histogram-based measures and one variance-based measure were tested and compared. The reference frame positions may be determined by an exhaustive search algorithm which is computationally complex. The complexity can be reduced by using a binary search algorithm which exploits the monotonicity of the distance measure with respect to the reference frame interval. The target bit allocation for each picture type in a group of pictures is adjusted to allow a variable number of reference frames with the constraint of constant channel bit rate. Simulation results show that the adaptive reference frame positioning scheme compares favorably with the fixed positioning scheme at the bit rates of 64 kb/s and 14.4 kb/s. 相似文献