基于Android平台的VoIP客户端开发与性能改进

发布时间：2018-04-04 13:44

本文选题：VoIP　切入点：回声消除　出处：《南京邮电大学》2017年硕士论文

【摘要】：Android操作系统是近年来最热门且发展最快的手机操作系统。本文设计并实现了一款基于Android平台的VoIP(Voice over Internet Protocol)客户端,并在其中增加回声消除算法,提升了VoIP的通话质量,使系统的性能得到改进。论文的主要工作包括:(1)深入研究VoIP的技术原理和其所用的关键技术,特别是SIP协议、回声消除技术等。(2)利用Android操作系统提供的NDK(Native Development Kit)框架设计并开发了Android平台下VoIP客户端。客户端主要完成了注册功能、拨打和结束电话功能及接听电话功能。(3)针对影响VoIP通话质量的回声问题,在语音处理模块中加入了回声消除功能以提高通话质量。回声消除算法以SPEEX协议栈中的MDF(Muti-delay Frequency Domain)算法为基础,增加了两种同步信号的方法。一种是在输入/输出端划出若干个专用的缓冲区,添加预取过程;另一种是用两个变量分别作为传入声卡的远端信号帧的序列号和本地采集帧的序列号,通过比较两个变量的大小关系修正预取的过程。(4)对本文设计的VoIP客户端进行测试,检验所设计的各项功能。测试结果表明,客户端的各项功能运行稳定、操作简单,且回声得到明显消除,提高了通话质量。
[Abstract]:Android operating system is the most popular and fastest growing mobile operating system in recent years.In this paper, we design and implement a VoIP(Voice over Internet protocol client based on Android platform, add echo cancellation algorithm to it, improve the quality of VoIP communication and improve the performance of the system.The main work of this paper includes: (1) deeply studying the technical principle of VoIP and its key technologies, especially SIP protocol, echo cancellation technology, etc.) using the NDK(Native Development framework provided by Android operating system, we design and develop the VoIP client in Android platform.The client mainly completes the registration function. The function of dialing and closing calls and answering calls. 3) aiming at the echo problem affecting the quality of VoIP calls, the echo cancellation function is added to the voice processing module to improve the quality of calls.The echo cancellation algorithm is based on the MDF(Muti-delay Frequency Domain algorithm in the SPEEX protocol stack, and two methods of synchronizing signal are added.One is to create several special buffers at the input / output end to add the prefetching process; the other is to use two variables as the sequence number of the remote signal frame of the incoming sound card and the sequence number of the local acquisition frame, respectively.The VoIP client designed in this paper is tested and tested by comparing the prefetching process of the two variables.The test results show that the functions of the client are stable, the operation is simple, the echo is eliminated obviously, and the communication quality is improved.
【学位授予单位】：南京邮电大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN916.5;TP311.52

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