Design And Implementation Of UAV Real-time HD Image Transmission System

The drone image transmission system is an important part of the drone.With the wide application of drones in aerial photography,photography,security,agriculture,power,and movies,drone image transmission systems have also received more and more attention.They need long-distance and stable transmission of video.The traditional drone image transmission system uses Wi-Fi to transmit video,and the transmission distance is short.When the drone has a long flight distance,there is a problem that video cannot be transmitted.To solve these problems and combine the characteristics of drone long-distance flight,high real-time requirements and low payload,this thesis proposes to design a kind of UAV real-time high-definition image transmission system that no limit of video transmission distance,low latency,light weight,and achieving real-time control.Aiming at the problem that traditional drone image transmission systems cannot transmit video over long distances because of the small Wi-Fi coverage,a real-time image transmission system for drone based on 4G network is proposed.Different from the traditional UAV image transmission system which used Wi-Fi to transmit video signals;this UAV real-time image transmission system utilizes a complete 4G network infrastructure and is designed in a modular manner.The C/S software system structure is used.Three modules in this UAV image transmission system,there are: sending module,server module and ground receiving module,wherein the sending module is further divided into an image acquisition module and a push module.By sending the video data collected by the sending module to the server module,the ground receiving module requests and plays the video to solve the problem of long-distance video transmission.In view of the huge data volume of video can not directly push from UAV,Dedicated video processing chip HI3518 E was used in sending module to sharpen and denoise the video.Then the integrated H.264 encoder was used to compress the video.Design and implement the push module,and use the real-time streaming media transmission protocol RTSP to send the encoded video data to the streaming server.Thus,the forwarding function was implemented and the problem of network congestion due to insufficient bandwidth was avoided.For the demand of low latency,proposes to make a frame loss optimization scheme and improve the sending module and the server module.For the delay problem of the push module,a "consumer-producer" model was proposed,which use the lock,ring buffer,and key frame drop optimization to guarantee the real-time performance of the push module.Solve the problem of the client-side delay by using the H.264 coding character.Propose to optimize the current keyframes in the server,and ensure that the client can obtain the current picture from the UAV in real time and no blurred screen.For the demand of achieving real-time control,a ground station system was designed and the video playback function was integrated into the ground station.Use Qt software’s graphical interface design capabilities and use C + +,VLC streaming media video library and open CV technology to achieve the functions of the ground station,including map implementation,serial communication,UAV positioning,real-time video playback,waypoint planning,and UAV commands Console,etc.Based on the studied technologies and methods,a real-time image transmission system for UAV was designed and implemented.Through the system test,the validity of the system is verified.The high-definition image delay is about 300 milliseconds,which can well meet the technical requirements of the UAV real-time image transmission system.