The Design And Implementation Of Network Video System Based On Linux

This paper describes the contents of the Linux operating system on the realization of a video networking system. The so-called video networking system means a new system using network as a platform for new digital information transmission and video playback system. Through the network, the broadcasted programs achieve long-distance transmission.The aim to develop the system is to realize the real-time publish of information. We can announce urgent information, unexpected happenings, TV shows, weather, sports, policy, legislation, foreign exchange of bank, flight number, train number, and so many real-time information. Previously, messages were broadcast through single PC, messages could not be update in time, so the contents were very simplex, and the PC was inconvenient to preserve. When problems turn up, special workers need to presence to solve the problem, which increases costs. The use of Digital Multimedia Broadcast conquers the difficulties, realizes the messages' real time broadcasting, and is convenient to preserve.The finance trade of China is in the face of situation of opportunity and challenge. More active finance market and the increase of business kinds bring opportunity for bank to develop quickly. At the same time, market open up, bank enter the market, the acceding of foreign bank is bound to aggravate the competition of the field of finance, which bring up higher requisition of service quality and working efficiency. Following the information-based period, the importance of finance information, transmitting efficiency gradually increased, which becomes the focus of the competition of banks. On the period of the lack of customer, the competition for customer will become the major competition between banks. But the achievement for solving the satisfactory of the customer is slight. When you stand in a queue to fetch money, you always have to wait for a long time, you have nothing to do during this time. Digital Multimedia Broadcasting system will broadcast video for you while you are waiting. With which will attract clients, increase the business of the bank. It is also a good way for the bank to be in a superiority place.The Digital Multimedia Broadcasting system consists of managing flat-top, server and client, among which there are two servers. The DMBServer and FTPServer. First we need to register a client group, then add client messages to the group, when succeed, we still need to add a designate client's order, distribute a client ID, and than produce play tasks for the client. Managing flat-top is responsible for delivering play list to DMBServer, it delivers tasks the client to broadcast to DMBServer. At the same time it delivers the source file to FTPServer. After receiving the information, the DMBServer stores them of the database. The client connects to DMBServer through socket to register itself. After successfully registration, the client sends request to DMBServer for play list, which includes client ID and the md5 value of play list. According to the client ID, DMBServer looks for tasks and produce play list. And then produce md5 of the play list. Compare the two. If they are equal, it means that the play list is the newest, than the DMBServer send OK0 to client. If they are not equal, the DMBServer send OK1 to the client, also the new play list. After receiving the play list, the client decompress it, read the play list and download the corresponding source file from FTPServer, and then broadcast the file. The client sends a heartbeat packet to server in fixed time to make clear that it is still alive. The server knows that after receiving the packet.Through extensions, the client's video player can play almost all the popular audio and video formats. Compared to other broadcasters, it occupies very little resources. It can broadcast many media formats without any system decoder. The support for MPEG/Xvid/DivX format is particularly good..The paper first introduces the need for video compression and compression principle and so on. The operating system used on client is the self-develop Linux system named LFS, from the application point of view, Linux is open source, beneficial for independence software producer to exploit application software which makes use of hardware efficiently, and the function is more powerful, and also convenient for profession consumer to develop their own secure, controllable systems. The main reason for choosing LFS is to develop a system which satisfies our demands. Only software needed is installed to avoid too huge of system. One advantage of LFS is that we can develop a tiny Linux system. When install a Linux release edition, people are forced to install many applications may not be used forever, which wastes disk spaces, to make matters worse, the CPU occupation.POSIX thread is a powerful method to enhance code response and performance. Similar to process, it is managed by time pieces according to the kernel. The thread shared the same memory space. Different thread can access same variable in the memory. So, all the threads in the program can read and write the global variable declared. Thread is rapid, compared to the standard fork functions, the expenses of thread are less. The kernel does not need to copy the process's memory space or file describer, which saves much CPU times.The use of md5 is to avoid the duplicate download of play list. The DMBServer judge the md5 messages it received and it produces, if equal, the DMBServer do not need to send the play list to the client, for it is not update, if not, send the play list.The rest of the paper introduces the realization of the server and the client. First introduces the server's functions and work processes, then analyzes the realization of the four threads. List the flow chart of each thread. From the registry of the client, connect to the DMBServer through socket, send different kinds of request packets to DMBServer, then download the play list and resource files to broadcast.The system realizes the broadcast of video on Linux operating system successfully. Transplanting the system to the embedded board, the system can be used at shopping center, bus station and banks, broadcasting information. There are vast market spaces in this field.