Phone Screen Projection System Design And Implementation Based On WebRTC Technology

The rapid development of mobile Internet of Things and the application of relevant technologies promoted screen projection technology, especially that of the mobile phone. However, the cross-platform compatibility of various screen projection technologies is unsatisfactory. Server end and client end must have achieved the technology so that relevant screen projection technologies can be used. These technologies have high demands for the hardware and software, so a more compatible mobile phone screen projection technology is urgently needed in existing market.To solve the problem, a mobile phone screen projection system based on Android platform via The Web real-time communication(WebRTC) technology is studied in this thesis. The system will be able to encode and compress the screen captured from Android phone with VP8 format, and deliver it to client end in real-time display via network. The client end is a program supported by API on the basis of Web layer in WebRTC. Google, Mozilla and Opera have integrated related API in WebRTC, so any platforms with the three explorers can realize mobile phone screen projection service provided that the Android phone installed this program.Under the premise that mobile phone screen projection has realized by WebRTC technology, to further improve the sending end's rate of convergence and enhance congestion control's performance under packet loss, an algorithm, dynamic adjustment to sending end's rate on the basis of Google Congestion Control(GCC), is put forward in this thesis. GCC has been regarded as the congestion control model of WebRTC. In low rate of convergence, optimization algorithm could dynamically adjust sending end's rate according to the difference value between receiving end's max bandwidth and sending end's current code rate. But in high rate of convergence, I frame instead of P frame is delivered. Comparative tests under WiFi proved that optimization algorithm's rate of convergence is 300 ms faster than GCC's when packet loss rate is less than 2%, and 285 ms faster than GCC's when packet loss rate is more than 10%, and optimization algorithm's code rate is 300 Kbps faster than GCC's when packet loss rate keeps 2-10%. As a whole, the optimization algorithm improves the performance of the screen projection system, and accelerates the congestion control's rate of convergence.