Development And Performance Improvement Of VoIP Client Based On Android

Android operating system has become the most popular and fastest growing mobile phone operating system in recent years.This paper has designed and realized the VoIP client based on Android and improve its performance by echo cancellation algorithm.The main work in this paper includes:Firstly,this paper starts with a study of the theory and technology key of VoIP,especially SIP and echo cancellation technique.Secondly,combined with Android 's NDK(Native Development Kit)framework,this paper has designed and implemented the VoIP client based on Android.The main achievement of the client are the registration function and the call functions,including sending a call,answering a call and hanging up the phone.Thirdly,in order to improve quality of the speech,echo cancellation is added to the voice processing modules.Two methods of synchronizing signals based on the MDF(Muti-delay Frequency Domain)algorithm in the SPEEX are proposed to eliminate the echo.On the one hand,a number of special buffers are set at the input / output so that the process of prefetch technique can be added.On the other hand,compare two values of variable used as the serial number of the remote signal frame and the local collection frame to fix the process of prefetch.Finally,through the numerous tests of VoIP clients,it is proved that this the VoIP client basically achieve the goals of various functions and it is stable,and easy to operate.Moreover,the echo is eliminated and the quality of the speech is improved.