共查询到20条相似文献，搜索用时 15 毫秒
1.
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
2.
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
3.
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
4.
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
5.
LIU Yun-qiang YU Song-yu WANG Xiang-wen ZHOU Jun 《浙江大学学报(A卷英文版)》2006,7(4):543-548
INTRODUCTION Many emerging video applications, such as video-on-demand (VOD) and distance learning, rely on the efficient transfer of compressed video. For the same average bandwidth, variable bit rate (VBR) encoded video streams have higher perceivable qual- ity and greater opportunity for statistical multiplexing gains compared to constant bit rate (CBR) video streams (McManus and Ross, 1996). However, VBR video typically shows significant burstiness on mul- tiple time scales, due … 相似文献
6.
针对AdHoc网络的视频传输,提出了一种新的网络带宽预测及控制方案．该方案基于跨层、接收端反馈以及贝叶斯网络等技术．对视频传输过程进行公式化描述,从而推导出影响视频传输质量的几个主要因素,这些因素可以通过跨层机制或接收端反馈的方式获取．根据这些影响因素,确定变量集和贝叶斯网络拓扑结构,从而构建贝叶斯网络预测模型．预测结果作为AdHoc网络带宽,根据该带宽值来控制视频编码器,动态调节输出的实时视频流码率．为验证该方案,对整个视频通信系统进行了仿真．结果显示,跟传统的传输方案相比较,夺方案能更好地利用网络带宽,减少了数据包的丢失,提高了实时视频质量． 相似文献
7.
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
8.
INTRODUCTION With the development of novel wireless tech- nologies and increasing available bandwidth, multi- media applications over wireless networks become attractive for both businesses and end users. Fast de- ployment of Wi-Fi HotSpots, increase in wireless coverage of remote habitable areas (Wi-Max, or wireless mesh networks), improved data services over the 2G cellular systems and the long awaited debut of 3G wireless services offer many potential and inter- operable communicatio… 相似文献
9.
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
10.
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
11.
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
12.
可伸缩视频编码通过码流提取获得子码流以适应不同的网络带宽和处理终端。本文提出一种基于内容描述的视频码流提取框架,根据预处理获得视频内容的描述指导可伸缩视频的码流提取,从而获得更符合视频内容的子码流。实验表明这种方法快速有效,能够在不损失编码效率的前提下保证视觉质量。 相似文献
13.
网络视频监控系统研究 总被引：2，自引：0，他引：2
视频监控系统是安全防范系统的组成部分，它是 一种防范能力较强的综合系统。视频监控系统在公 安、金融证券、银行、商店、宾馆、智能大厦以及重要部 门、社区的安全方面能起到重要的作用。目前，广泛应 用的监控系统采用模拟技术。近年来，随着计算机、 网络以及图像处理、传 相似文献
14.
CHOU Philip A 《浙江大学学报(A卷英文版)》2006,7(5):737-748
INTRODUCTION Many applications, such as software distribution, Internet TV/video streaming, video conferencing, multiplayer gaming, personal media distribution and P2P web content duplication, distribute the same content from one source node to many destination nodes. For these applications, IP multicast is an ideal network layer solution. A distribution tree rooted at the source can be formed to reach an arbitrary number of receivers. During content distribution, every single piece of… 相似文献
15.
The new H.264 video coding standard achieves significantly higher compression performance than MPEG-2. As the MPEG-2 is popular in digital TV, DVD, etc., bandwidth or memory space can be saved by transcoding those streams into H.264 in these applications. Unfortunately, the huge complexity keeps transcoding from being widely used in practical applications. This paper proposes an efficient transcoding architecture with a smart downscaling decoder and a fast mode decision algorithm. Using the proposed architecture, huge buffering memory space is saved and the transcoding complexity is reduced. Performance of the proposed fast mode decision algorithm is validated by experiments. 相似文献
16.
1 Introduction Scalable coding has already been recognized as aneffective solution to resolve the network’s bandwidthvarying[1].It is also i mportant for video transmissionin error-prone environments , congest-prone networkand network with varying quality of service ,such aswireless video transmission systems .So it plays a veryi mportant role in both network communication andwireless communication. MPEG-4 video standard supports fine granularityscalability ( FGS) fine granularity scalabil… 相似文献
17.
INTRODUCTION Video content will be the main contributor to the future traffic in multimedia applications. Camcorders, digital cameras and lately mobile phones with video capturing capabilities have resulted in a wide spreading of multimedia to the masses. Quality of the captured/rendered videos is likely to be the major determining factor in the success of the new multi- media applications as well as product differentiation. Video processing chain includes video capturing, video pre-proce… 相似文献
18.
The 3rd generation partnership project (3GPP) has defined the protocols and codecs for implementing media streaming services over packet-switched 3G mobile networks. The specification is based on IETF RFCs on audio/video transport. It also adds new features to achieve better adaptation to the mobile network environment. In this paper, we propose an algorithm for handover detection and fast buffer refill that is based on the existing feedback and signaling mechanisms. The proposed algorithm refills the receiver buffer at a faster pace during a limited time frame after a hard handover is detected in order to achieve higher video quality. 相似文献
19.
结合空时OFDM和转换编码技术,提出了一种无线衰落信道下具有可分级转码能力的鲁棒视频传输方法.采用可分级转码器将高质量的MPEG-2压缩视频转换为低码率、低分辨率MPEG-4可分级码流来满足网络带宽和终端设备显示的要求.在接收端采用一种层干扰抑制算法,使得分层空时OFDM系统不同层的传输性能存在差异,从而使系统具有不对等保护能力.根据分级码流的重要程度不同,将转码输出的可分级码流分别由分层空时编码OFDM系统的不同层来实现视频的鲁棒传输.实验结果表明:在典型的随机突发错误的无线环境下,提出的具有可分级转码能力的系统的视频传输性能优于传统的非分级转码的视频传输系统. 相似文献
20.
Agnes Kukulska‐Hulme Anne Jelfs Elizabeth Mallett Dawn Holland 《Learning, Media and Technology》2004,29(2):125-137
The paper gives a brief overview of the use of digital video in distance education, the background to The Open University's Digital Video Applications (DiVA) Project, the contexts in which the Digital Video Library system is being used and some evaluation findings. Through DiVA, the university is investigating how it can use its video assets effectively, to support reuse of existing materials in course production. The project team is also evaluating student use of the system. The paper reports on an observation study which revealed several usability issues and stakeholders' opinions about potential uses of the DiVA system. This is followed by findings from an evaluation of student use of the system at a residential school and its use as part of an online learning activity undertaken by students accessing the system remotely. Evaluation findings to date indicate some quality and workload issues but they also show opportunities that come to light when using the DiVA system. 相似文献