摘 要
电话业务是电信的主要业务，除此之外，电信还对广大用户提供了额外的语音，视频等增值业务。目前的增值业务多为语音增值，以后随着网络的发展会有更多的如视频等增值业务被挖掘出来。在电信行业中语音增值处理由早期的全人工处理，到现在已经演变成为自动处理和人工处理并存。自动处理的实现主要依赖于一种新兴的技术-计算机电话集成技术，计算机电话集成技术是随着计算机技术和电话技术的发展促成的，它实现了利用计算机来控制电话，呼叫，路由，为呼叫提供计算机所能访问的媒体资源等功能。
本论文重点讨论了基于API的媒体网关的相关技术及系统的设计，开发情况。基于API的媒体网关是一套电信增值业务平台的子系统。其功能主要是管理平台所需要的硬件资源，处理来自公共电话网上的呼叫，路由，信令，并为呼叫提供语音服务，如播放文件，字串等。本论文对媒体网关涉及到的CTI，信令技术做了详细介绍，之后对系统的四个子模块：维护模块，中继处理模块，语音处理模块，设备连接模块的概要设计做了详细介绍，然后对系统的核心模块语音处理模块做了重点描述。
本系统的开发应用了C++编程语言，数据库系统采用的Sybase。
关键字：计算机电话集成，信令，语音处理
Design And Programme With The Media GateWay Based On API
ABSTRACT
The telephone business is the main business of the telecoms. In addition, the telecoms provide additional voice and video increment business to the large customer also. Currently most of the increment businesses are increment businesses of voice, but more and more increment businesses such as increment businesses of video will be scoop out along with the development of networks. The increment businesses of voice are all manually processed from earlier period in the telecommunication area, which till now have already turned into that automatic processing and manual handling exist at the same time. Auto voice processing is carried out by the development of a newly arisen technique named Computer Telephony Integration technique, Computer Telephony Integration is developing along with the development of computer technique and telephone technique, it carries out to make use of a computer to control a telephone, call, route, and provides the media resources that the computer can visit for the call.
The paper mainly talks about the related techniques and design of the media gateway system based on API. The media gateway system is a sub-system of the telegraphy increment business development platform. Its main functions are to manage platform’s hardware resources, process calls, route, signal from PSTN, and provide voice services for the call, such as play a file or string etc. This paper presents detailed introduction of the signal techniques related to media gateway firstly, and then introduces the design of the four sub-modules of media gateway system based on API, where the four sub-modules are: Oam Module, Dit Module, Voice Module. At last the paper gives a detailed introduce of the core module (voice process module) of the media gateway
The development of this system uses C++ programming language, and uses database system of Sybase.
Keywords：Computer Telephony Integration, Signals, Voice Process
本课题的研究内容主要是以硬件厂商所提供硬件资源为基础，调用其接口API，实现高级功能，提供如Playfile,CreateConference等功能接口给增值业务开发商使用，完成具体的增值业务。
随着增值业务的逐渐丰富，做多媒体交换机的厂商也越来越多。各式各样的多媒体资源板卡越来越多。增值业务开发平台提供商设计开发基于API的媒体网关可选的硬件也越来越多，选择合适的板卡，或者多媒体交换机做硬件基础，主要从板卡所提供的资源容量及价格来衡量。目前用得比较多的多媒体板卡主要是国外的Dialogic及NMS公司所产的。Dialogic公司是全球CTI产品著名的供应商。其产品将计算机和通讯紧密地结合在一起，实现信息访问，消息处理及本地网和广域网的互联。Dialogic和NMS的板卡在增值业务平台上使用的比较早，可靠性比较高，价格也相对较高，国内目前也有做这类多媒体交换机的厂商，国内厂商所开发的板卡价格有优势，可用来做小规模业务开发的硬件基础。
传统的媒体网关概念上来说，由四部分组成：线路卡、代码转换引擎、网关控制器以及分组网络接口，一个媒体网关只能使用本地的资源，这样对于资源无法均衡调配，在市场的激烈竞争以及要求保持系统灵活性的条件下，开放式系统能够提供专有系统和背板所不具有的多级适应性，设计开放式的媒体网关，是目前一个重要的研究方向。
