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1.
本文针对MPEG VBR多媒体流量的特征,结合小波和卡尔曼滤波的特点,在新的网络流量预测模型的基础上,提出了一种新的多媒体流自适应带宽分配算法,并在NS仿真平台中实现该算法。结果表明,该算法能够有效避免网络拥塞,降低网络传输时延,减少数据丢包率,明显地提高了带宽利用率,具有较好的实时性,支持QOS。 相似文献
2.
Some high-speed protocols such as HSTCP have been proposed to improve the ability of bandwidth utilization in high-speed networks. However, the increased scalability of high-speed TCP leads to many dropped packets in a single loss event in drop tail environment. In addition, there exists burstiness on short time scales that may cause lots of packets loss. In this paper, we analyze the problem of packet loss, and then propose ACWAP (Adaptive Congestion Window Adjustment plus Pacing) algorithm to reduce the loss rate of high-speed TCP. Along with pacing algorithm for avoiding burstiness on short time scales, ACWAP uses delay information to estimate the network state and adaptively changes the increase parameter to 1 before congestion to reduce the number of dropped packets. Many simulation results show our proposed algorithm can reduce the number of dropped packets in a single loss event, alleviate synchronized loss phenomena and improve the RTT unfairness while keeping the advantages of high-speed TCP. 相似文献
3.
In this paper, we propose a novel optimal quality adaptation algorithm for MPEG-4 fine granular scalability (FGS) stream over wired network. Our algorithm can maximize perceptual video quality by minimizing video quality variation and increasing available bandwidth usage rate. Under the condition that the whole bandwidth evolution is known, we design an optimal algorithm to select layer. When the knowledge of future bandwidth is not available, we also develop an online algorithm based on the optimal algorithm. Simulation showed that both optimal algorithm and online algorithm can offer smoothed video quality evolution. 相似文献
4.
In this paper, we propose a novel optimal quality adaptation algorithm for MPEG-4 fine granular scalability (FGS) stream over wired network. Our algorithm can maximize perceptual video quality by minimizing video quality variation and increasing available bandwidth usage rate. Under the condition that the whole bandwidth evolution is known, we design an optimal algorithm to select layer. When the knowledge of future bandwidth is not available, we also develop an online algorithm based on the optimal algorithm. Simulation showed that both optimal algorithm and online algorithm can offer smoothed video quality evolution. 相似文献
5.
Totransmitthemultimediadataovertheinternet ,pre encodedvideobitstreamsarepreferablebecauseofthelimitofthenetworkbandwidth .Inmostcases ,theencodershouldknowthechannelcharacteristicsinad vanceandencodethemasparameters .Consequently ,theflexibilityisreduced .Theratecontrolisemployedtocontroltheoutputbitrateaccordingtonetworkcondi tions.Forwirelessnetworks ,theirbandwidthsaremuchmorelimitedthanwirenetworks.Soratecontrolbecomesespeciallyimportantfortransmittingmultimediaoverthewirelessdomains[1- … 相似文献
6.
提出了一种以 FA RIMA( p,d,q)模型为基础 ,对 MPEG VBR业务在综合业务网络传输的带宽进行动态分配的新方法 .FARIMA( p,d,q)模型既可描述业务的长相关特性 ,又可描述业务的短相关特性 ,以其为基础的业务预测较准确 .文中对建模和预报方法进行了简化 ,并通过仿真进行了验证 .结果表明本方法可减少对缓冲区的需求 ,并减少了丢包率 相似文献
7.
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
8.
INTRODUCTION Streaming of multimedia data over the Internet has rapidly increased in recent years. All commercial applications and most research in video streaming use conventional hybrid video coding. To adapt the data transmission rate on the server to the varying bandwidth caused by congestion in the Internet or to different available bandwidths of different clients, the simulcast solution is widely applied (Balk et al., 2003; Feamster et al., 2001; Schierl and Wiegand, 2004). A larg… 相似文献
9.
INTRODUCTION With the emergence of wireless technology, various multimedia services, e.g., audio and/or video, are reaching us today through portable devices any- time, anywhere and even more increasingly accessi- ble in the near future. High quality video streaming over wireless IP is one of the most attractive applica- tions by ongoing deployment of wireless local area network (WLAN) hotspots and even powerful Wi- MAX mobile coverage. However, the present Internet is not providing a… 相似文献
10.
CHAKARESKI Jacob 《浙江大学学报(A卷英文版)》2006,7(5):773-783
INTRODUCTION According to yearly statistics the demand for multimedia traffic over computer networks is con- stantly on the increase (Nielsen//NetRatings, http:// www.nielsen-netratings.com/). Therefore, it is inevi- table that situations where different media streams will need to share communication resources will be- come commonplace. In such cases, it would be of interest to optimize the overall performance of the network. In other words, resources should be allo- cated across the com… 相似文献
11.
Interactive transport of multi-view videos for 3DTV applications 总被引：1，自引：0，他引：1
The authors propose a novel method for transporting multi-view videos that aims to keep the bandwidth requirements on both end-users and servers as low as possible. The method is based on application layer multicast, where each end point receives only a selected number of views required for rendering video from its current viewpoint at any given time. The set of selected videos changes in real time as the user‘s viewpoint changes because of head or eye movements. Techniques for reducing the black-outs during fast viewpoint changes were investigated. The performance of the approach was studied through network experiments. 相似文献
12.
INTRODUCTION Video multicasting over wireless local area net- work (WLAN) (IEEE Standard 802.11, 1997) enables the distribution of live or pre-recorded programs to many receivers efficiently. An example application is to redistribute TV programs or location-specific in- formation in hot spots such as airport. Users can watch their favorite TV programs on mobile devices while browsing the Internet. For enterprise applica- tions, an example is multicasting video of a lecture or trainin… 相似文献
13.
Ian White 《British journal of educational technology : journal of the Council for Educational Technology》2010,41(3):420-431
It is recognised that the teaching of complex psychomotor skills using online delivery is difficult without the support of either face‐to‐face coaching and tuition or a stereoscopic viewing system that provides users with a feel for the spatial nature of the skills being taught. To date, the limitations of bandwidth, and the high cost and sophistication of existing three‐dimensional video production and viewing technologies have limited the use of stereoscopic video imaging to highly funded fields, such as sports and medical research or military applications. The advent of desktop video editing software, along with personal video players (such as the Apple iPod and iPhone) with small screens utilising efficient video codecs, means that high‐quality video podcasts can now be effectively created and delivered via the Internet. Combining these new video technologies with a conventional analogue stereo viewing and capture system makes the production of stereoscopic video potentially much more accessible to educators as a practical teaching tool. This paper seeks to alert educational designers to an exploratory study into a potentially useful methodology for the capture, production, dissemination and viewing of stereoscopic video images using existing, low‐cost technologies. Aside from the production of a simple viewer, the process is straightforward and requires only basic and readily available equipment. Applications in education as well as vocational and sports training are self‐evident. 相似文献
14.
Frame skipping in low bit video coding could significantly reduce the visual quality of reconstructed video. At the same time, if the complexity of the video sequence remains high for a long period, then driving up the long term average bit rate, the only resort of MPEG-4 Q2 rate control algorithm results in using a high quantization scale, which shows a poor visual quality of the reconstructed video. This paper analyzes the main causes of frame skipping in current MPEG-4 frame rate control scheme, and presents a new rate control algorithm based on the quadratic R-D model over a CBR channel. Key features of the present work are. 1) the bits allocated to each P-frame or B-frame are in proportion to its distance from the end of this GOP, i.e. more bits are allocated to the frames that are nearer to their reference Ⅰ -frame: 2) the target buffer level is changeable in the GOP, at the end of each GOP( five P-frames or B-frames), the target buffer level is linearly reduced from 1/2 to 1/4 of buffer size, to other frames, the target buffer level is set to 1/2 of buffer size: 3 ) a selective and judicious use of the reduced resolution mode, in addition to a modulation of the quantization scale parameter, is to control the average long term bit rate. Experimental results with different video sequences of varied complexity, encoded at low bit rates show better efficacy of the proposed algorithm than MPEG-4 Q2 rate control scheme, and the experimental results also show that the improved algorithm has significantly reduced the number of frame skipping, increased the overall PSNR, and improved the perceptual quality. 相似文献
15.
黄凯锋 《牡丹江教育学院学报》2010,(5):108-109
本文主要以网络广泛应用的客户/服务器作为应用模型,在考虑网络状态的基础上,通过引入客户端缓冲区状态,提出了一种针对视频点播系统的流量控制机制。该机制将网络拥塞控制和客户端缓冲区控制策略结合起来对视频服务器发送速率进行自适应调整,保证了发送码率的平滑,更好地满足了客户端的需求,提高了网络带宽利用率。 相似文献
16.
LI Mao-quan XU Zheng-quan 《浙江大学学报(A卷英文版)》2006,7(12):2057-2062
INTRODUCTION Currently, main video coding algorithms, such as H.26x and MPEG families are all based on block discrete cosine transform (BDCT). At low bit rate, all these BDCT-based algorithms suffer from visible blocking artifacts, which are easily noticeable as the discontinuities between neighboring blocks, particu- larly in flat and low activity homogeneous areas of the image because high frequency DCT coefficients are inclined to be quantizd to zeros due to the high quan- tizatio… 相似文献
17.
基于小波分析的红外弱小目标检测算法 总被引：1，自引：0，他引：1
针对红外弱小目标检测需求,根据红外弱小目标图像特性及其小波分析特性,提出了一种基于小波分析的红外弱小目标检测算法。算法首先对红外弱小目标图像进行小波分解;然后置低频小波系数为零去除背景,阈值化高频小波系数滤除噪声,自适应子带增强加强目标能量;最后进行小波逆变换并进行自适应阈值分割。实验结果表明,提出的算法速度快、抑制噪声的能力强。 相似文献
18.
The effect of receiver buffer size on perceived video quality of an Internet video streamer application was examined in this work. Several network conditions and several versions of the application are used to gain understanding of the response to varying buffer sizes. Among these conditions local area versus wide area, bandwidth estimation based versus non-bandwidth estimation based cases are examined in detail. A total of 1000 min of video is streamed over Internet and statistics are collected. It was observed that when bandwidth estimation is possible, choosing larger buffer size for higher available bandwidth yields quality increase in perceived video. 相似文献
19.
为了提高视频文件中水印算法的透明性和鲁棒性,在此提出了一种基于数据块间关系的水印嵌入算法,该方法以数据块之间的特定关系表示水印的比特值,从而避免了将水印值直观地嵌入原始的视频文件中。在介绍该水印算法的详细设计过程后,给出了水印的嵌入过程和提取过程,最后对设计的水印算法进行了透明性和鲁棒性的测试,测试结果表明该算法在高比特率的情况下具有较高的透明性。对于大部分常见的水印攻击方法具有较强的鲁棒性,但对于降低视频图像分辨率的攻击方法,水印的鲁棒性还有待提高。 相似文献
20.
Low energy consumption is one of the main challenges for wireless video transmission on battery limited devices. The energy invested at the lower layers of the protocol stack involved in data communication, such as link and physical layer, represent an important part of the total energy consumption. This communication energy highly depends on the channel conditions and on the transmission data rate. Traditionally, video coding is unaware of varying channel conditions. In this paper, we propose a cross-layer approach in which the rate control mechanism of the video codec becomes channel-aware and steers the instantaneous output rate according to the channel conditions to reduce the communication energy. Our results show that energy savings of up to 30% can be obtained with a reduction of barely 0.1 dB on the average video quality. The impact of feedback delays is shown to be small. In addition, this adaptive mechanism has low complexity, which makes it suitable for real-time applications. 相似文献