共查询到16条相似文献,搜索用时 515 毫秒
1.
2.
《计算机应用与软件》2016,(9)
无线信道时变特性引起的缓冲区占用度波动对视觉质量的影响,使得自适应视频播放算法不仅需要考虑缓冲区的占用度,还要考虑缓冲区占用度的波动。提出一种面向安全区域的平滑自适应播放算法SAO-AMP,采用缓冲区的占用度及其波动程度作为触发条件。首先,根据预估接收速率和缓冲区的预期波动情况设置播放速率的调整期,达到平滑视频播放速率的目的。其次,调整播放速率的同时监测缓冲区的占用度,使缓冲区占用度处于预设的安全区域内。实验结果表明,SAO-AMP算法不仅平滑了播放速率的变化,还能控制缓冲区占用度的波动范围。与基于缓冲区占用度的AMP算法相比,SAO-AMP算法的速率调节次数和丢包率均减小了30%,且算法在信道状态变化较大的情况下,依然能很好地工作。 相似文献
3.
从信宿端的角度来解决视频媒体的同步连续播放,提出了一种自适应的动态媒体播放算法.分析了马尔可夫调制的泊松到达情况下的排队模型,给出了缓冲区门限的选取原则,最后提出了通过用不连续性和播放失真的方差来衡量同步性能方法,实验结果表明,该算法的同步性能优于Yuang的算法.通过选择合适的参数,可有效地防止缓冲区下溢造成的播放停顿以及缓冲区上溢造成的播放跳跃,从而实现同步平滑播放. 相似文献
4.
针对AMP-Live模型中存在的问题,提出一种基于报文延迟预测的自适应媒体播放算法(NEWAMP),采用未来信道和缓冲状态的预测值作为视频报文播放速率调整的依据,将速率变化的程度进一步细化,同时考虑应用要求的最大端到端延迟,提高算法性能,与传统播放算法相比,NEWAMP在保证报文因下溢和上溢而丢弃的概率足够小的前提下,缓冲延迟减小了约50%,而与普通AMP-Live方法相比,NEWAMP不仅减小了报文因下溢和上溢而丢弃的概率,还将缓冲延迟减小了约40%。实验结果证明了该算法的有效性。 相似文献
5.
6.
针对无线网络中可伸缩视频传输存在的问题,提出一种基于客户端下溢概率估计的传输算法.算法通过统计当前播放缓冲区容量的变化情况,计算出缓冲区下溢的概率,以此为根据选择合适的视频发送层数,从而在充分利用有效带宽的同时尽可能减少视频下溢频率.仿真结果表明,该算法能够保证在无线网络中视频传输具有较低的下溢概率和较高的视频质量. 相似文献
7.
8.
双重控制策略在流媒体连续播放中的应用 总被引:1,自引:1,他引:0
传统的发送速率控制和播放速率控制由于各自的局限性,很难克服网络时延扰动对流媒体连续播放的影响.为了改善播放系统的性能,将双重控制策略应用到流媒体播放中,在发送端发送速率控制采用了内模控制器以克服传输延迟的影响,在接收端播放速率控制采用了简单的PID控制器,两种控制共同调节缓冲区长度.实验表明该方法能够处理传输时延和网络扰动引起的失步对播放的影响,缓冲区长度能够稳定在合理的区间,有效地防止缓冲区下溢造成的播放停顿以及缓冲区上溢造成的播放跳跃.发送速率变化率较小,有利于避免网络拥塞的发生.尤其是在网络出现大的扰动时,与其他方法相比,控制效果更加理想,播放更加流畅. 相似文献
9.
10.
11.
12.
This paper aims to reduce the amount of prebuffering required to ensure a maximum video continuity in streaming. Current approaches do this by slowing the playout frame rate of the decoder, this is known as adaptive media playout (AMP). However, doing this introduces playout distortion to the viewers as the video is played slower than its natural playout rate. We approach this by proposing a frame rate control scheme that jointly adjusts the encoder frame generation rate of the encoder and the playout frame rate of the decoder. In addition to using AMP to improve video continuity, we also allow the encoder to increase the encoder frame generation rate. This means the encoder will be sending more frames to the decoder to quickly increase the number of frames available at the playback buffer, thus lowering the chance of buffer underflow which causes discontinuity in video playback. At the same time, the increase in the number of frames at the playback buffer may mean that the decoder does not need to use AMP to delay the playback, thus lowering the playback distortion. However, the increase in encoder frame generation rate comes at a price because frame quality will need to decrease in order to meet the constraint on available network bandwidth. This implies that the scheme needs to find the optimal trade-off between frame quality, playout distortion and video continuity. To do that, we characterize the frame rate control problem using Lyapunov optimization. We then systematically derive the optimization policies. We also show that these policies can be decoupled into separate encoder and decoder optimization policies, thus allowing for a distributed implementation. Simulation results show significant reductions in the prebuffering requirements over a scheme that perform no frame rate control and lower playout distortions compared to the AMP schemes, while exhibiting a modest drop in frame quality. 相似文献
13.
To improve the playout quality of video streaming services, an arrival process-controlled adaptive media playout (AMP) mechanism is designed in this study. The proposed AMP scheme sets three threshold values, denoted by P n , L and H, for the playout controller to start playback and dynamically adjust the playout rate based on the buffer fullness. In the preroll period, the playout can start only when the buffer fullness n is not less than the dynamic playback threshold P n ,?which is determined by the jitters of incoming video frames. In the playback period, if the buffer fullness is below L or over H,?the playout rate will slow down or speed up in a quadratic manner. Otherwise, the playback speed depends on the instantaneous frame arrival rate, which is estimated by the proposed arrival process tracking algorithm. We employ computer simulations to demonstrate the performance of the proposed AMP scheme, and compare it with several conventional AMP mechanisms. Numerical results show that our AMP design can shorten the playout delay and reduce both buffer underflow and overflow probabilities. In addition, our proposed AMP also outperforms traditional AMP schemes in terms of the variance of distortion of playout and the playout curve. Hence, the proposed arrival process-controlled AMP is really an outstanding design. 相似文献
14.
针对无线网络存在的自相似特性会影响视频流的播放质量问题,提出了基于滑动窗口的接收端播放缓存调整算法,根据网络流量的变化,动态地调整双门限,并利用播放缓存的占用率来控制视频流的播放速度,平滑时延抖动.仿真实验证明,无论网络流量处于平稳状态还是处于突发状态,本文设计的算法都能够较好地保证视频流的连续播放,提高视频流的播放质量,为用户提供良好的视觉效果. 相似文献
15.
Multimedia applications including video data require the smoothing of video playout to prevent potential discontinuity. In this paper, we propose a dynamic video playout smoothing method, called the Video Smoother, which dynamically adopts various playout rates in an attempt to compensate for high delay variance of networks. Specifically, if the number of frames in the buffer exceeds a given threshold (TH), the Smoother employs a maximum playout rate. Otherwise, the Smoother uses proportionally reduced rates in an effort to eliminate playout pauses resulting from the emptiness of the playout buffer. To determine THs under various loads, we present an analytic model assuming the Interrupted Poisson Process (IPP) arrival. Based on the analytic results, we establish a paradigm of determining THs and playout rates for achieving different playout qualities under various loads of networks. Finally, to demonstrate the viability of the Video Smoother, we have implemented a prototyping system including a multimedia teleconferencing application and the Video Smoother performing as part of the transport layer. The prototyping results show that the Video Smoother achieves smooth playout incurring only unnoticeable delays. 相似文献
16.
Ya-Fan Su Yi-Hsuan Yang Meng-Ting Lu Chen H.H. 《Multimedia, IEEE Transactions on》2009,11(7):1331-1339
Client-side data buffering is a common technique to deal with media playout interruptions of streaming video caused by network jitters and packet losses of best-effort networks. However, stronger playout interruption protection inevitably amounts to larger data buffering and results in more memory requirements and longer playout delay. Adaptive media playout (AMP), also a client-side technique, can reduce the buffer requirement and avoid buffer outage but at the expense of visual quality degradation because of the fluctuation of playout speed. In this paper, we propose a novel AMP scheme to keep the video playout as smooth as possible while adapting to the channel condition. The triggering of the playout control is based on buffer variation rather than buffer fullness. Experimental results show that our AMP scheme surpasses conventional schemes in unfriendly network conditions. Unlike previous schemes that are tuned for a specific range of packet loss and network instability, the proposed AMP scheme maintains consistent performance across a wide range of network conditions. 相似文献