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Java-based embedded network video server

    

Network video servers use TCP / IP protocol, audio and video data from embedded LAN or the Internet server to the client, users can use the IE browser or client software on the network video equipment for a visit to watch a real-time image.

SAMSUNG is to the company S3C2410 development as the core circuit board expansion of the external interface, and the combination of Java technology WEB embedded video surveillance equipment.

A system of hardware structure


 S3C2410 system as the center, external storage devices including two 32 M of SDRAM, 64M of NAND Flash and 2 M of NOR Flash. Peripheral interfaces, including serial port, JTAG debug interface and USB interface, USB interface connector responsible for the video camera data collection, video capture device hardware structure in Figure 1.

2 network video server architecture and implementation

WEB-based streaming media system include: streaming media services provide the server and browser used to monitor the client. Server and client browser via HTTP protocol communications, in Figure 2. One major streaming media server by the three-tier structure comprising: WEB servers, network interface and drive module.


2.1 the realization of the underlying drive


USB camera drivers between video capture application with the USB core of the Linux kernel between the middle layer. First, USB camera to the USB drive their own core registration information, call USB core and the API function for the upper deck; Second, the application by calling the USB camera-driven interface function to a set of video acquisition and restructuring Parameters such as camera operators. Figure 3 USB is the key driver for data structure usb_driver entrance of the main drivers of data structure and function.

2.2 streaming media service of the process of achieving


The process used to open a server port, and continue to monitor ports, if the request is connected establish a connection, set up after the process of streaming media services will continue to provide port to the acquisition of image data flow also receive client sent from the image adjustment Order parameters. Its main program flow in Figure 4. One of the most critical to achieve include:

(1) to initialize VdIn structure

VdIn camera equipment described in the integrity of information, including all V4L standards defined in the function interface and data structure, but also some additional parameters for image acquisition. Initialization VdIn function as follows:
init_videoIn (& videoIn, videodevice, width, height, format, grabmethod)
The function will videodevice, width, height, format, grabmethod, and so passed to VdIn structure in the videoIn.

(2) the creation of image acquisition thread

Image acquisition to achieve a separate thread, in the main thread in a thread of the acquisition are as follows:
pthread_create (& w1, NULL, (void *) grab, NULL);
One created by the pthread_create grab thread is the realization of part of image acquisition.

(3) socket connection initialization

Socket communications in the socket to be initialized:
serv_sock = open_sock (serverport);
In open_sock function include: create a socket, bind socket and the port number and began monitoring ports and other steps. Its implementation process-oriented and connected to the same socket communications.

(4) create a service-threaded socket

When the monitoring service after the main process responsible for the continuous cycle of listening to receive the request and the establishment of a new client connecting socket, a socket for this communication process.
new_sock = accept
(Serv_sock, (struct sockaddr *) & their_addr, & sin_size));
pthread_create (& server_th, NULL, (void *) service, & new_sock);

(5) create a network communication thread

Thread in the network communications, including: image data sent and the client image adjustment parameters of acceptable 2. The client sent the image adjustment parameters, including image brightness and contrast, this provides communications data format, with a bit different bytes that the brightness and contrast, the corresponding bit 0 or 1 that reduce or increase the brightness or contrast value. Read through the socket of the function to receive client sent the adjustment parameters, and save the message:
ret = read (sock, (unsigned char *) & message, sizeof (stmct client_t));
Socket write function through the client wrote to the image data frame, the following headerframe is to send the image frame:
ret = write_sock (sock, (unsigned char *) headerframe, sizeof (struct frame_t));

Application of 2.3 Java Applet


Implementation of the system Java Applet three features: images transmitted through the socket to the client display, the client will adjust image parameters sent to the server; client will click on the movement control parameters sent to the server. Figure 5 depicts the basic framework of multi-threaded socket communications. Init function and the start of the Applet at the beginning of the implementation of call, start by creating two threads:  socket for communication; provide the user interface displayed images and the user operation. User interface design to use Sun's SwingWorker class library.

In the client's browser window enter the mobile monitoring equipment, IP addresses and connect, if one is the first link in the mobile monitoring equipment, there will be a Web server to download a Java Applet, and the Applet will be prompted to the relevant authority of the Security.®é¢˜.

3 Conclusion

Based on Web browser and Java Applet technology, the control interface, the need for monitoring software, easy to use. ARM9 CPU system, through direct video processing and transmission, simplifying the circuit design and costs. Based on Java Applet network video server solutions, with practical applications further extensions can be applied to the large number of wired or wireless video surveillance areas.


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