SIP-based Video Communication System On Android

Nowadays, multimedia technology is widely used, VOIP technology has been greatly developed, and have shown great potential, especially in domestic market. The upgrading of broadband and increasing of WIFI hotspot by domestic telecom operators will bring VOIP to a new stage of development. There are two main VOIP signaling protocol:H.323and SIP. Compared with H.323, SIP protocol which based on the Internet standards and protocols with the advantage of concise, open, readability, interoperable and scalable, has a vast space in the field of video communication. With the development of VOIP, the mobile terminal will be an important part of it. At present, there are severer operate system of mobile terminal, while the most important is Android. It’s more and more popular to develop SIP application on Android. However, the quality of communication based on SIP has not a good solution.Aimed at the problems of NAT and tolerance for wireless video communication quality, this paper studied the adjustment of the packet loss rate. It used STUN to solve the problem of traversing NAT devices in communication, called Android NDK for encoding and decoding, and designed a SIP terminal system of video communication on Android platform. The important job of this article:1. Solve the NAT traversal problem. Because of the serious lack of IP address and caring of security, there are many NAT devices in the Internet, which prevents the establishment of SIP-based video communication. This paper used the method of STUN to solve the problem of NAT. The experiment showed that the method can work well with Cone NAT which shares98.1%of all NAT devices.2. Solve inefficient problem of JAVA. As we all know, the Android system only support JAVA for direct development, while its bottom is implemented by C/C++. In order to run fast and efficient in do encoding and decoding of video data, this paper introduces the Android NDK, use the JNI mechanism to port the existing encoder and open source decoder to the Android platform. Which significantly reduce delay of the encoding and decoding in video communication process, to ensure the quality of video communicate. In the experimental environment the experimental results show that the terminal system can get relative smooth vide and clear images, and do not fell obvious delay while the resolution is set to240*240. 3. Try to adjust the packet loss rate. In wireless network environment, it is difficult to guarantee the quality of video communication, and that became harder when get through the NAT device. As the change of the size of the send packets and the frequency of sending packet, the packet loss rate of video data in communication showed great difference. The packet loss problem is serious when the data packet is large and the transmission frequency is high. To solve this problem, the article attempts a statistics-based packet loss rate adjust method in the experiment. The experimental results show that the packet loss rate can be control in less than3%by adjusting the size of the data packet and the frequency of sending data packet in the experimental environment.