Research And Implementation Of Network Video Intercom System Based On SIP Protocol

With the popularization and development of Intelligent Community in China, the traditional independent and separated subsystems of communities gradually reveal many drawbacks, and can no longer satisfy people's increasing demand for services. People now is looking for a integrated system which incorporates all the features of the traditional subsystems and provides users with many features like property information release, video intercom, video surveillance, audio and video on demand and home control.In this paper, we discussed some key technologies needed by the integrated system like signaling control between the communicating terminals and transmission of multimedia information and solved the following key issues:1. The online registration and behaviour control of the terminals in the system. Based on SIP protocol, we generate the request messages between terminals to coordinate their behaiviours.2. Synchronous control between send and receive parts:the two parts are both under the control of the unified clock and adjust the behavior of sending and receiving threads based on the packets'rate.3. audio and video synchronous problem: Play thread control the playback rate based on the time stamp of the packets, in order to achieve synchronization of audio and video playback; 4. voice and video latency and jitter issues:the software design introduces a modular thought and a pipe mechanism to prevent the transmission pipeline pipeline congestion, reducing the audio and video delay and jitter.Generally speaking, this paper mainly made the following achieves:we designed the general architecture and communication model of its subsystem----video intercom system,, we achieved the routing of calls and media consultation between the terminals through the control of SIP signaling and encoding of audio and video compression and real-time transmission by adopting the relevant standards and protocols. Algorithms of audio and video synchronization and send and receive synchronization were designed to ensure the clear and smooth audio and video transmission, we also adopted the pipeline mechanism to improve the efficiency of real-time transmission. Test results show that the system fully realized the needed functions and performances, and comparing to the traditional video intercom systems, it is more secure and stable, easier to wired and more extensible, it can provide more personalized services to meet the various needs of the users. Moreover, thanks to the SIP standard protocol of NGN, it allows the system to easily integrate with next-generation systems and provides more personalized services.