ATM网传送MPEG—2的方法

ＡＴＭ网传送ＭＰＥＧ－２业务是远程教育，ＶＯＤ、远程医疗等网络服务的基础。由于ＭＰＥＧ－２具有很高的压缩比，因此它对丢失、时延有很高的要求。ＡＴＭ网在传送ＭＰＥＧ－２业务时的关键是如何满足ＭＰＥＧ－２对丢失和时延的特定要求。本文对ＡＴＭ传送ＭＰＥＧ－２的适配方法、打包策略、定时恢复及排队策略进行了综述。     

支持隔行扫描的两步DCT域视频水印算法

提出了一种在隔行扫描MPEG-2视频流中嵌入DCT域水印的算法。该算法对MPEG-2中DCT变换按帧和按场进行的两种情况采用不同的扩频码进行嵌入和检测,使水印的检测基本不受DCT方式变化的影响,从而能够抵抗各种重编码攻击,同时也保持了良好的实时性。还采用了两步算法,即除水印数据外还同时嵌入了少量同步信息,这样既可定期更新用于水印数据的扩频码,从而提高算法的安全性与灵活性,同时在存在帧插入／删除等攻击时又不会因失去同步而导致检测失败。     

MPEG-2视频编码技术

本文介绍了动态图像专家组标准系列中MPEG 2视频标准的概念、组成以及特点 ,MPEG 2压缩编码的原理、技术 ,MPEG 2视频编码码流概念及其数据结构     

MPEG-2 MP@HL高清实时解码器的VLSI设计实现

研究了可用于高清数字电视的MPEG-2MP@HL解码器的设计与ASIC实现。解码器芯片的最高位流速率可达到80Mbps。采用了并行流水线技术架构,可有效地减小处理时延,降低时钟频率;具有合理的存储器总线仲裁方案,可降低缓存器的大小;采用了并行总线架构,可保证足够的带宽,不需提高存储器的总线传输频率,从而减小电路的功耗。采用0．18um工艺成功进行了流片.     

An adaptive compressed MPEG-2 video watermarking scheme

Digital watermarking is becoming more and more important for protecting the authenticity of multimedia objects as they become easier to copy, exchange, and modify. Several watermarking schemes have been proposed in recent years, but most of them deal with still images, only some being extended over to the temporal domain for video watermarking. But again most of those approaches are applied to uncompressed video processing domain. In the subject paper, a new compressed video watermarking procedure is proposed. The developed method embeds several binary images, decomposed from a single watermark image, into different scenes of a video sequence. The spatial spread spectrum watermark is embedded directly into the compressed bit streams by modifying discrete cosine transform (DCT) coefficients. In order to embed the watermark with minimum loss in image fidelity, a visual mask based on local image characteristics is incorporated. Extensive experimental simulations demonstrate that the proposed watermarking scheme is substantially more effective and robust against spatial attacks such as scaling, rotation, frame averaging, and filtering, besides temporal attacks like frame dropping and temporal shifting.     

无线视频传输中自适应的前向纠错技术

提出了一种改进的无线网络视频传输自适应前向纠错(FEC)算法.该算法首先对丢包原因进行区分,根据不同的丢包原因采用不同的带宽估计方法,使得获得的网络拥塞导致丢包的概率更加准确;然后根据视频的不同部分在解码端重要性的不同,在视频数据和冗余数据之间优化分配所估计的带宽,使得在当前网络条件下视频的失真最小.仿真结果表明,这种算法能够更好地提高网络的吞吐量和视频的服务质量.     

Grand alliance MPEG-2-based video decoder with parallel processing architecture

A practical and unique hardware architecture for video bitstream source decoding and video postprocessing of a Moving Pictures Expert Group (MPEG-2)-based high-definition television (HDTV) compressed bitstream has been implemented to impose minimal limitations on the video source coding algorithm. The Grand Alliance (GA) MPEG-2-based HDTV codec achieves a high degree of source and channel coding efficiency while preserving the delivery of high-resoultion picture quality in a variety of video input and output formats in bandwidth-limited channels. The video source decoder hardware architecture necessary to achieve the data decoding and ensuing video postprocessing poses numerous technologic challenges to the system designer, who must tradeoff minimizing codec constraints with the eventual commercialization of a video decoder for a consumer television receiver product. The powerful and flexible coding algorithm necessary to satisfy the HDTV picture quality and transmission channel bandwidth limitation requirements results in an encoder-output bitstream that necessitates high throughout decoding. Although the transmitted bitstream is of constant rate due to rate buffering, bistreams internal to the codec are both peaky and bursty. An intelligent distributive parallel processing decoding architecture has been developed to dynamically partition the MPEG-2 bitstream into a number of decodable subset bitstreams, while placing minimal constraints on the encoding algorithm. This architecture allows for high-speed, efficient decoding of the bitstream, and can be a prelude to the development of a cost-effective consumer product. Further architecture refinements can be explored, including implementation in VLSI.     

Error recovery in video transmission over CDMA2000 broadcast networks

Multimedia services over a CDMA2000 broadcast network face a challenge from the unreliable and error-prone nature of the radio channel. Reed-Solomon (RS) coding, integrated with the MAC protocol, is used to cope with this problem. However, performance analysis of RS coding under varying channel conditions shows that it is not always effective, especially for slow-moving nodes which experience relatively long error bursts. Therefore a more efficient scheme is proposed that uses a RS code with reduced parity overhead, and freeing bandwidth can be used flexibly for retransmission. The packets to be retransmitted are prioritised by a utility function derived from the map of the error control block at each mobile node and the number of mobile nodes that require the lost packet. Simulation results show that the gain of retransmission exceeds the loss incurred by reducing the parity, leading to an improvement in the playback quality of MPEG-4 video streams. As a result, service area for high-quality multimedia can be expanded.     

MPEG-4 video verification model: Status and directions

This article describes the current status and future directions of the emerging ISO MPEG-4 audiovisual coding standard. The article first presents an overview of the different aspects of the standard and then focuses on the video coding aspects. The current status of the Video Verification Model (VM) (a completely defined encoder and decoder specification) is described in detail and its performance is presented. The new functionalities supported by this emerging standard and their potential applications are highlighted. © 1997 John Wiley & Sons, Inc. Int J Imaging Syst Technol, 8, 468–479, 1997     

Robust end-to-end loss differentiation scheme for transport control protocol over wired/wireless networks

The authors propose a robust end-to-end loss differentiation scheme to identify the packet losses because of congestion for transport control protocol (TCP) connections over wired/wireless networks. The authors use the measured round trip time (RTT) values to determine whether the cause of packet loss is because of the congestion over wired path or regular bit errors over wireless paths. The classification should be as accurate as possible to achieve high throughput and maximum fairness for the TCP connections sharing the wired/wireless paths. The accuracies of previous schemes in the literature depends on varying network parameters such as RTT, buffer size, amount of cross traffic, wireless loss rate and congestion loss rate. The proposed scheme is robust in that the accuracy remains rather stable under varying network parameters. The basic idea behind the scheme is to set the threshold for the classification to be a function of the minimum RTT and the current sample RTT, so that it may automatically adapt itself to the current congestion level. When the congestion level of the path is estimated to be low, the threshold for a packet loss to be classified as a congestion loss is increased. This avoids unnecessary halving of the congestion window on packet loss because of the regular bit errors over the wireless path and hence improves the TCP throughput. When the congestion level of the path is estimated to be high, the threshold for a packet loss to be classified as the congestion loss not to miss any congestion loss is decreased and hence improves the TCP fairness. In ns 2 simulations, the proposed scheme correctly classifies the congestion losses under varying network parameters whereas the previous schemes show some dependency on subsets of parameters.     

A transfer learning framework for traffic video using neuro-fuzzy approach

One of the main challenges in the Traffic Anomaly Detection (TAD) system is the ability to deal with unknown target scenes. As a result, the TAD system performs less in detecting anomalies. This paper introduces a novelty in the form of Adaptive Neuro-Fuzzy Inference System-Lossy-Count-based Topic Extraction (ANFIS-LCTE) for classification of anomalies in source and target traffic scenes. The process of transforming the input variables, learning the semantic rules in source scene and transferring the model to target scene achieves the transfer learning property. The proposed ANFIS-LCTE transfer learning model consists of four steps. (1) Low level visual items are extracted only for motion regions using optical flow technique. (2) Temporal transactions are created using aggregation of visual items for each set of frames. (3) An LCTE is applied for each set of temporal transaction to extract latent sequential topics. (4) ANFIS training is done with the back-propagation gradient descent method. The proposed ANFIS model framework is tested on standard dataset and performance is evaluated in terms of training performance and classification accuracies. Experimental results confirm that the proposed ANFIS-LCTE approach performs well in both source and target datasets.     

Speed limit and ramp meter control for traffic flow networks

The control of traffic flow can be related to different applications. In this work, a method to manage variable speed limits combined with coordinated ramp metering within the framework of the Lighthill–Whitham–Richards (LWR) network model is introduced. Following a ‘first-discretize-then-optimize’ approach, the first order optimality system is derived and the switch of speeds at certain fixed points in time is explained, together with the boundary control for the ramp metering. Sequential quadratic programming methods are used to solve the control problem numerically. For application purposes, experimental setups are presented wherein variable speed limits are used as a traffic guidance system to avoid traffic jams on highway interchanges and on-ramps.     

一种基于相似度的汉语语言模型平滑技术及其在音字转换中的应用

针对汉语语言模型中的数据稀疏问题,利用词语语义信息,将词语相似度同back-off平滑技术相结合,提出一种基于词语相似度的汉语语言模型平滑技术,并且设计了一种能够自动优化模型中各项参数的迭代算法,最后,将这种平滑技术由低阶语言模型推广到高阶语言模型中,将上述技术应用到音字转换领域.实验表明,这项技术使语言模型的性能获得了较大的提高,并有效地降低了音字转换系统的错误率.     

Multi-modal social networks for modeling scientific fields

This paper analyzes whether methods from social network analysis can be adopted for the modeling of scientific fields in order to obtain a better understanding of the respective scientific area. The approach proposed is based on articles published within the respective scientific field and certain types of nodes deduced from these papers, such as authors, journals, conferences and organizations. As a proof of concept, the techniques discussed here are applied to the field of ‘Mobile Social Networking’. For this purpose, a tool was developed to create a large data collection representing the aforementioned field. The paper analyzes various views on the complete network and discusses these on the basis of the data collected on Mobile Social Networking. The authors demonstrate that the analysis of particular subgraphs derived from the data collection allows the identification of important authors as well as separate sub-disciplines such as classic network analysis and sensor networks and also contributes to the classification of the field of ‘Mobile Social Networking’ within the greater context of computer science, applied mathematics and social sciences. Based on these results, the authors propose a set of concrete services which could be offered by such a network and which could help the user to deal with the scientific information process. The paper concludes with an outlook upon further possible research topics.     

Radial basis function method for 1-D and 2-D groundwater contaminant transport modeling

In this paper we develop a meshless method for modeling groundwater contaminant transport. The algorithm uses collocation method with radial basis functions. Numerical results are presented for several cases: pure diffusion; advection and dispersion for continuous source; advection and dispersion for instantaneous source; advection and dispersion for patch-source. The results show that the method is very simple and accurate.Jichun Li likes to thank the UNLV Research Office for the NIA grant support for this project. This work is also partially supported by Nevada EPSCoR. The authors are very grateful to the reviewers for their valuable comments on improving this paper.     

Bayesian networks for maritime traffic accident prevention: Benefits and challenges

Bayesian networks are quantitative modeling tools whose applications to the maritime traffic safety context are becoming more popular. This paper discusses the utilization of Bayesian networks in maritime safety modeling. Based on literature and the author's own experiences, the paper studies what Bayesian networks can offer to maritime accident prevention and safety modeling and discusses a few challenges in their application to this context. It is argued that the capability of representing rather complex, not necessarily causal but uncertain relationships makes Bayesian networks an attractive modeling tool for the maritime safety and accidents. Furthermore, as the maritime accident and safety data is still rather scarce and has some quality problems, the possibility to combine data with expert knowledge and the easy way of updating the model after acquiring more evidence further enhance their feasibility. However, eliciting the probabilities from the maritime experts might be challenging and the model validation can be tricky. It is concluded that with the utilization of several data sources, Bayesian updating, dynamic modeling, and hidden nodes for latent variables, Bayesian networks are rather well-suited tools for the maritime safety management and decision-making.     

高架复合道路交通噪声的动态模拟及特征分析

基于高架复合道路的噪声及其对周围环境的各种影响因素,结合声波的传递衰减建立动态的仿真模型。由此计算实时噪声的等效声级及统计声级;为取得高架复合道路一侧垂直面和水平面的声场分布,在模拟分析中,也考虑多车道、车速、交通量、声屏障高度、林带布置等各种因素影响。     

Economic evaluation of traffic safety measures for transport companies

This paper addresses the economic feasibility of measures to reduce the material damage of transport companies. Results are presented of a series of interviews among transport companies as well as from a postal questionnaire survey. Next, calculations are presented for three types of companies: a small family company, a large family company and a large formalised company. From the viewpoint of costs and benefits, damage prevention measures appear to be particularly interesting to larger companies. Small companies, being the largest group, tend to have an informal culture in which measures are less effective. Especially those measures for which no large investments are needed, which influence the behaviour of drivers and need not to be contracted out, are perceived as attractive by the transport companies.     

Current-reinforced random walks for constructing transport networks

Biological systems that build transport networks, such as trail-laying ants and the slime mould Physarum, can be described in terms of reinforced random walks. In a reinforced random walk, the route taken by ‘walking’ particles depends on the previous routes of other particles. Here, we present a novel form of random walk in which the flow of particles provides this reinforcement. Starting from an analogy between electrical networks and random walks, we show how to include current reinforcement. We demonstrate that current-reinforcement results in particles converging on the optimal solution of shortest path transport problems, and avoids the self-reinforcing loops seen in standard density-based reinforcement models. We further develop a variant of the model that is biologically realistic, in the sense that the particles can be identified as ants and their measured density corresponds to those observed in maze-solving experiments on Argentine ants. For network formation, we identify the importance of nonlinear current reinforcement in producing networks that optimize both network maintenance and travel times. Other than ant trail formation, these random walks are also closely related to other biological systems, such as blood vessels and neuronal networks, which involve the transport of materials or information. We argue that current reinforcement is likely to be a common mechanism in a range of systems where network construction is observed.     

Performability indicators for the traffic analysis of wide area networks

In this paper, a repairable circular consecutive-k-out-of-n:F system with one repairman is studied. It is assumed that the working time and the repair time of each component are both exponentially distributed and every component after repair is ‘as good as new’. Each component is classified as either a key component or an ordinary component. Key components have priority in repair when failed. By using the definition of generalized transition probability, the state transition probabilities of the system are derived. Important reliability indices are evaluated for an example.