| In recent years, with the continuous development of science and technology and the continuous improvement of people’s living standard, people’s understanding and requirements of the field of smart home have also changed. Doorbell is an indispensable part of the smart home. Because the rapid development of network and transmission technology, and wireless networks such as 3G, Wifi become more widely, receiving the information of visitors and doing video intercom with visitors at the mobile terminal are beginning to be applied.In this thesis, an intelligent remote visual doorbell system based on SIP protocol was designed after combined the current status and the development trend of the doorbell system. The doorbell system has realized many functions such as the audio and video intercom, recording visitors’ photos, leaving the voice messages of visitors, controlling access remotely. This system consists of door machine, indoor machine, mobile phone and other mobile terminals, and they are all working on the Android platform. In order to achieve the functions of system, the main work of this thesis is as follows:1. Through the analysis of the requirement of system, selecte the hardware platform of outdoor and indoor machine. And transplant u-boot, Android operating system, yaffs2 file system on the hardware platform.2. Research and analyze the session control protocol SIP and the session description protocol SDP, and analyze the processes of osip and eXoisp protocol stack. And transplant the protocol stacks in software to achieve the session control module.3. Design the software structure of the visual doorbell system. Based on the research and transplantation of PRT protocol stack ortp and open-source audio and video codec library Mediastreamer2, realize the audio and video codec module and RTP stream transmission module of the system. Design and implemente the service modules such as the module of recording visitor’s photo and voice message, the module of database and so on. Design and implement user-friendly UI interface.4. In order to solve the ineffective issue of echo cancellation caused by the synchronization problem of recording and playback thread, research and analysis the echo cancellation algorithm of speex, and raise a kind of thread synchronization method based on tag speech frame to determine delay frames, can effectively eliminate the echo.5. Test the system. Mainly test the functions of system and the performance of audio and video calls. The rusults show that the system has reached the design target, and the system run stability. |
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