| Now in teaching classrooms,the traditional projectors connect to computers commonly by wire for teaching activities,but this way is only suitable for one-way teaching,which will hinder the interaction between students and teachers and the fluency of the teaching activity.In the modern classrooms,it will change the traditional way of one-way teaching,and students will be the main roles.Students can take advantage of e-books,notebooks,tablets,mobile phones or other terminal devices to get the course-ware.And students can project their screens of terminal devices on a wireless projector,and teachers can also guide students with remote control and so on.Researches at home and aboard have presented a variety of technologies and solutions about wireless projection,and among the existing products,the related wireless projection servers also have existed.But for the modern education's needs such as real-time screen transmission,split-screen display with multiple sources,and remote control,these solutions and products support incompletely.And the synchronization delay would be 300ms or more,and the frame per second would be not large which leads to less fluent.This issue for the demands of the modern teaching,researches and designs the wireless projection server based on Android,which uses wireless real-time screen transmission and remote control technology.It meets the projected demands,interaction needs and sharing needs in the modern courses,breaking the shackles of traditional teaching mode.At the same time,it can also connect to the traditional projectors with VGA or HDMI.The main content and innovation of this paper includes:(1)Proposing a wireless projection solution for the modern teaching demands.Designing the control protocol,the media data transmission protocol,and the extensible software architecture for the wireless projection server.Meeting the needs consist of wireless real-time screen transmission,split-screen display with multiple sources,remote control,Web management,and video projection.(2)Proposing and designing the policy of UDP packets transmission and the automatic adjustment mechanism for the frame rate.Optimizing synchronization delay,with the results:with the screen resolution of 1280*768,the synchronization delay is less than 100ms,and with the screen resolution of 800*600,the synchronization delay is about 50ms.Guaranteeing the synchronization delay in the performance,increasing the frame rate(such as 60fps)to improve the fluency.(3)Implementing the wireless projection server's control module,and the media transmission module,decoding and rendering module with JNI,and implementing the policy of UDP packets transmission and the automatic adjustment mechanism for the frame rate.Finally,through the functional and performance testing,verifying the high real-time performance and stability of the wireless projection server. |
