基于SIP协议的视频通话系统的研究与实现

许多基于IP的多媒体应用都需要创建并管理会话过程。基于SIP协议的视频通话系统实现通过SIP协议来建立和管理视频通话的会话。围绕基于SIP协议的视频通话系统展开需求分析、系统设计、系统实现和系统测试。该研究可应用于在智能通讯、生活娱乐等领域,具有一定的实际意义。     

SIP协议在视频监控系统中的应用

在当前的视频监控市场中,不同监控系统采用的信令控制协议不统一,互联互通困难,无法满足网络化时代对大规模电信级视频监控、远程访问、集中管理的需要.于是设计者们将目光投向了通用的SIP协议与H.323协议.H.323由于其协议族过于复杂庞大,不如SIP简单灵活、分布式控制,故将SIP作为未来市场视频监控的主流协议已成为业界共识.中国电信集团也在其<中国电信家庭视频监控业务技术规范>中,推荐将SIP协议作为首选控制协议来实现.本文介绍了一整套基于SIP协议的视频监控系统应用解决方案,涵盖了系统的基本组成和各类信令的处理流程.在此方案中,视频监控将摒弃以往的私有协议,完全采用通用的SIP协议来实现,以利于日后不同监控系统之间的互联互通.     

基于μClinux的远程监控系统的设计与实现

本文设计了一种基于μClinux的远程监控系统。该系统通过USB摄像头采集视频数据,采用Video4Linux模块提供的编译接口进行视频采集程序的设计,经MPEG-4压缩算法对视频流进行压缩编码,通过实时传输协议(RTP)和实时传输控制协议(RTCP)配合使用实现流媒体数据的网络传输。整个系统建立在嵌入式架构上,能独立完成实时视频的采集、处理及传输功能,可广泛应用于远程监控系统、可视电话、工业控制等领域。     

嵌入式视频图像传输系统的设计与实现

本文介绍了一种基于嵌入式Linux和S3C2410平台的视频传输系统。该系统通过USB摄像头采集视频数据,采用Video4Linux模块提供的编译接口进行视频采集程序的设计,经MPEG-4压缩算法对视频流进行压缩编码,通过实时传输协议(RTP)和实时传输控制协议(RTCP)配合使用实现流媒体数据的网络传输。整个系统建立在嵌入式构架上,能独立完成实时视频的采集、处理及传输功能,可广泛应用于远程监控系统、可视电话、工业控制等领域。     

在Linux环境下SIP通信的实现

SIP(Session Initiatioan Protocol)协议是由IETF工作组于1997年7月提出的,是应用层的控制协议,能建立、调整和终止多媒体的呼叫和会话。SIP协议是基于文本方式的,即以明文方式传输。SIP消息包括请求消息、应答消息。SIP协议侧重于将IP电话作为因特网上的一个应用,并且也采用RTP作为媒体传输的协议。本文在SIP通信过程中,采用面向连接的TCP来传输SIP的交互信令,采用面向无连接的UDP协议进行实时音频流传输。本设计是在Linux操作系统下,用套接字(socket)来实现的。设计实现了SIP协议的整个通信过程。最后,提出了进一步开发的设想。     

WiMAX下的列调强拆SIP扩展方案

会话初始化协议(SIP)作为VoIP的主流会话控制协议,基本功能相对简单,不能满足无线列调核心业务的强拆需求。针对该问题,提出WiMAX网络环境下基于SIP协议的无线列调系统结构,对SIP协议消息类型和事务进行扩展,设计信令流程,并给出 SIP 客户端与服务端的扩展实现方案。实验结果表明,该方案满足铁路强拆通话建立的时间要求,可以成功实现强拆。     

在Linux环境下SIP通信的实现

SIP（Session Initiatioan Protocol）协议是由IETF工作组于1997年7月提出的，是应用层的控制协议，能建立、调整和终止多媒体的呼叫和会话。SIP协议是基于文本方式的，即以明文方式传输。SIP消息包括请求消息、应答消息。SIP协议侧重于将IP电话作为因特网上的一个应用，并且也采用RTP作为媒体传输的协议。本文在SIP通信过程中，采用面向连接的TCP来传输SIP的交互信令，采用面向无连接的UDP协议进行实时音频流传输。本设计是在Linux操作系统下，用套接字（socket）来实现的。设计实现了SIP协议的整个通信过程。最后，提出了进一步开发的设想。     

基于OMAP3530的SIP视频监控客户端设计与实现

在嵌入式Linux环境下设计实现一个由SIP信令控制的视频监控客户端。该系统以OMAP3530芯片为硬件平台核心,采用H.264作为视频编码标准,并将会话初始协议用于整个系统的信令控制。系统功能包括SIP注册与退出、SIP呼叫与挂断、音视频数据流控制、播放和存储等功能。该设计充分利用了H.264 算法标准在数据压缩率和网络友好性等方面的优势,并利用了OMAP3530双核架构的特性,由ARM核完成系统的管理和控制,DSP进行解码。实验结果证明,该方法建立的监控客户端具有高性能、低功耗、实时性强、运行稳定的特点。     

基于SIP的MCU视频会议系统的实现

目前的MCU视频会议主要基于H323标准,适合在专用网内进行部署。设计一种基于SIP的MCU视频会议系统,该系统在软交换网关和MCU分别进行H323和SIP信令互换;呼叫处理部分用标准的SIP信令来实现,业务逻辑用以SIP应用服务器控制,应用服务器与Web服务器间用TCP/IP通信,将会议的媒体处理单元(MCU)、终端、资源管理器、Web服务器有机的结合在一起。     

IP网的实时视频传输技术

探讨如何实现在IP网上的实时视频传输技术,并在UDP／IP及RTP／RTCP协议之上,提出了一种扩展的实时视频数据传输协议IRTP（Improved Real Time Protocol）。该协议设计简单,实现方便,利用该协议实现了对视频数据高效、实时的传输。     

Only connect: teaching, technology and telesis

Abstract This paper describes an approach to the design of interactive multimedia materials being developed in a European Community project. The developmental process is seen as a dialogue between technologists and teachers. This dialogue is often problematic because of the differences in training, experience and culture between them. Conditions needed for fruitful dialogue are described and the generic model for learning design used in the project is explained.     

European Community policy and the market

Abstract This paper starts with some reflections on the policy considerations and priorities which are shaping European Commission (EC) research programmes. Then it attempts to position the current projects which seek to capitalise on information and communications technologies for learning in relation to these priorities and the apparent realities of the marketplace. It concludes that while there are grounds to be optimistic about the contribution EC programmes can make to the efficiency and standard of education and training, they are still too technology driven.     

一种自适应子融合集成多分类器方法

融合集成方法已经广泛应用在模式识别领域,然而一些基分类器实时性能稳定性较差,导致多分类器融合性能差,针对上述问题本文提出了一种新的基于多分类器的子融合集成分类器系统。该方法考虑在度量层融合层次之上通过对各类基多分类器进行动态选择,票数最多的类别作为融合系统中对特征向量识别的类别,构成一种新的自适应子融合集成分类器方法。实验表明,该方法比传统的分类器以及分类融合方法识别准确率明显更高,具有更好的鲁棒性。     

Avoiding semantic and temporal gaps in developing software intensive systems

Development of software intensive systems (systems) in practice involves a series of self-contained phases for the lifecycle of a system. Semantic and temporal gaps, which occur among phases and among developer disciplines within and across phases, hinder the ongoing development of a system because of the interdependencies among phases and among disciplines. Such gaps are magnified among systems that are developed at different times by different development teams, which may limit reuse of artifacts of systems development and interoperability among the systems. This article discusses such gaps and a systems development process for avoiding them.     

Designing economic np control charts: A programmed simulation approach

This paper presents control charts models and the necessary simulation software for the location of economic values of the control parameters. The simulation program is written in FORTRAN, requires only 10K of main storage, and can run on most mini and micro computers. Two models are presented - one describes the process when it is operating at full capacity and the other when the process is operating under capacity. The models allow the product quality to deteriorate to a further level before an existing out-of-control state is detected, and they can also be used in situations where no prior knowledge exists of the out-of-control causes and the resulting proportion defectives.     

The development of robot art

Going through a few examples of robot artists who are recognized worldwide, we try to analyze the deepest meaning of what is called “robot art” and the related art field definition. We also try to highlight its well-marked borders, such as kinetic sculptures, kinetic art, cyber art, and cyberpunk. A brief excursion into the importance of the context, the message, and its semiotics is also provided, case by case, together with a few hints on the history of this discipline in the light of an artistic perspective. Therefore, the aim of this article is to try to summarize the main characteristics that might classify robot art as a unique and innovative discipline, and to track down some of the principles by which a robotic artifact can or cannot be considered an art piece in terms of social, cultural, and strictly artistic interest. This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008     

Explanation and prediction: an architecture for default and abductive reasoning

Although there are many arguments that logic is an appropriate tool for artificial intelligence, there has been a perceived problem with the monotonicity of classical logic. This paper elaborates on the idea that reasoning should be viewed as theory formation where logic tells us the consequences of our assumptions. The two activities of predicting what is expected to be true and explaining observations are considered in a simple theory formation framework. Properties of each activity are discussed, along with a number of proposals as to what should be predicted or accepted as reasonable explanations. An architecture is proposed to combine explanation and prediction into one coherent framework. Algorithms used to implement the system as well as examples from a running implementation are given.     

Three Process Perspectives: Organizations, Teams, and People

This paper provides the author's personal views and perspectives on software process improvement. Starting with his first work on technology assessment in IBM over 20 years ago, Watts Humphrey describes the process improvement work he has been directly involved in. This includes the development of the early process assessment methods, the original design of the CMM, and the introduction of the Personal Software Process (PSP)^SM and Team Software Process (TSP){^SM}. In addition to describing the original motivation for this work, the author also reviews many of the problems he and his associates encountered and why they solved them the way they did. He also comments on the outstanding issues and likely directions for future work. Finally, this work has built on the experiences and contributions of many people. Mr. Humphrey only describes work that he was personally involved in and he names many of the key contributors. However, so many people have been involved in this work that a full list of the important participants would be impractical.     

基于复小波噪声方差显著修正的SAR图像去噪

提出了一种基于复小波域统计建模与噪声方差估计显著性修正相结合的合成孔径雷达(Synthetic Aperture Radar,SAR)图像斑点噪声滤波方法。该方法首先通过对数变换将乘性噪声模型转化为加性噪声模型,然后对变换后的图像进行双树复小波变换(Dualtree Complex Wavelet Transform,DCWT),并对复数小波系数的统计分布进行建模。在此先验分布的基础上,通过运用贝叶斯估计方法从含噪系数中恢复原始系数,达到滤除噪声的目的。实验结果表明该方法在去除噪声的同时保留了图像的细节信息,取得了很好的降噪效果。     

How do children do mathematics with LOGO?

Abstract  This paper considers some results of a study designed to investigate the kinds of mathematical activity undertaken by children (aged between 8 and 11) as they learned to program in LOGO. A model of learning modes is proposed, which attempts to describe the ways in which children used and acquired understanding of the programming/mathematical concepts involved. The remainder of the paper is concerned with discussing the validity and limitations of the model, and its implications for further research and curriculum development.