The Design Of Voip And Video Transimission On The Embedded Linux Mobile Terminal

VoIP is integrated with wireless LAN into a new application technology VoWLAN.In the thesis, VoWLAN and video transmission are used in aircraft wearable digitalmaintenance equipment to provide security and efficient voice communication, not onlygive the user the convenience of wireless calls, but also effectively reduce the cost ofcommunication, improve the efficiency of communication. The paper is subsidized bythe subprojects of national major projects named large aircraft wearable digitalmaintenance system. The main work of the paper is as follows.1. The protocol of real-time transmission, SIP and SDP are studied preliminary atfirst, and then both ALSA architecture audio processing interfaces and one open sourceSIP protocol stack named oSIP/eXosip are introduced, before one VoIP client isdesigned to run on embedded Linux system.2. Both the four SIP transaction states machine and the transition mechanism arelearned and implemented for designing VoIP client. The hierarchical and modulardesign method is applied in the coding and debugging of VoIP client. And then thefunctions of initiating a calling, receiving a call are all able to achieve by operating thegraphical interactive interface. In additionally, the module of encrypting voice data isintegrated into the VoIP client to enhance the security of VoIP.3. According to the video for Linux two API specifications, the modules ofcapturing an image, recording video and transmitting video files are implemented to beable to run on embedded Linux system. And the frame buffer technology is adopted inthe module of capturing images to increase the speed of video capture. Because theARM9processor is short of computing power, both the look-up table and optimizingthe digital image processing algorithms are introduced to improve the performance ofthe image processing.4. Great deals of experiments have been carried on to test the performance ofembedded VoIP client. From the experiments, the issue of that call volume is to smallhas been found and resolved by a lot of analysis. And the module of encrypting voicedata is integrated into VoIP client to reduce the risks of leaks. The results of the experiments have demonstrated that the design of the VoIP clientand video transmission have met the requirements of the project. And at the end of thearticle, the other function modules maybe needed to expand has been discussed indetail.