Design of digital image remote monitoring system based on multi-point controller and A/D converter
“The system can use a multi-point control system (MCU) as the tandem center, connect with each monitoring point in the form of radiation, and process the image, voice and data of each monitoring point through the MCU to implement monitoring. The advantages of the whole system networking method are that the network structure is simple, the control is convenient, the connection is flexible, and the capacity expansion is rapid. However, the monitoring system needs a network communication platform with good security, high reliability, strong stability, capable of transmitting multimedia information, strong scalability, and in line with international standards. Therefore, there are three main requirements for the network.
2. Networking method
The system can use a multi-point control system (MCU) as the tandem center, connect with each monitoring point in the form of radiation, and process the image, voice and data of each monitoring point through the MCU to implement monitoring. The advantages of the whole system networking method are that the network structure is simple, the control is convenient, the connection is flexible, and the capacity expansion is rapid. However, the monitoring system needs a network communication platform with good security, high reliability, strong stability, capable of transmitting multimedia information, strong scalability, and in line with international standards. Therefore, there are three main requirements for the network.
The network has a larger bandwidth and a higher source compression ratio.
The network delay is small and the bit error rate is low.
In order to adapt to the development trend of the interactivity and flexibility of the network transmission system, it is required to implement multimedia monitoring and the network support system is required to be easy to expand and upgrade.
3. How it works
The digital image remote monitoring system can be divided into low-rate system and high-rate system according to the different needs of users. The low-rate system can provide image monitoring within 6B, and can adopt PSIN dedicated line, ISDN, B-ISDN and DDN methods. The high-speed system can guarantee the image monitoring of 6B~30B, but it needs to use more than 2M bandwidth lines to transmit various signals. The transmission methods include: E1 transmission method based on physical transmission network, high-speed optical fiber, wireless microwave, twisted pair of super five types and above, and leased public network 2M lines.
As shown in Figure 1, the detectors such as smoke and ventilation transmit the collected analog signal to the A/D converter, and the digital signal converted by the converter is transmitted to the image coding transmitter by RS232 or RS485.
The monitoring center is a respectable multi-point controller in each sub-control center, and is connected to the decoder through DDN/ISDN/E1/MW and other transmission methods. The video signal output by the central codec enters the picture processor. After it is divided, it outputs multi-channel video signal and sends it to the video wall or management station. Video switching means that the image processing device transmits the images collected by the camera of the terminal to the image encoding transmission device at certain time intervals. The device encodes and compresses the graphics according to a certain algorithm, and sends it to the multipoint controller (MCU) through DDN/ISDN/E1/MW and other lines. The MCU is similar to a small switch, it can provide multiple ports for the access of various monitoring signals of each sub-monitoring unit, and process the audio stream, video stream and data stream according to a certain algorithm. The MCU sends these signals to the upper-level monitoring center, data acquisition processor, CCTV or to the CRT via the codec through matrix switching.
LAN can use Ethernet or FDDI and other forms of networking. The data acquisition processor decodes the signal sent by the MCU and issues it to the LAN. The monitoring center or sub-monitoring center can realize friendly connection with the local MIS network or other networks. Local MIS users can access the video signals collected by the monitoring system through the video server. The main function of the video server is video-on-demand (VOD), and at the same time realizes online user video access management and video access deployment management. The video server in this system is responsible for the intelligent information processing of the whole network, and the cooperative work of multiple processors is realized through the modular design. Users can order video programs on the video server through the network. Usually, you can choose a video server suitable for a small or medium-sized network, and the number of users is between 0~50 or 50~1000. The video server responds to the user’s request and transmits the video program to the computers of each workstation in the form of video stream. In this way, each workstation can browse and send commands (such as: turn the camera 50 degrees to the left, and vertically drop 2 cm) and so on. The command is compiled by software, uploaded on the LAN and sent to the decoder for decoding, and then sent to the image encoding transmission device through MCU switching, optical fiber and other transmission lines. The device interprets the command as a control signal and sends it to the PTZ to direct the camera to work, thus realizing remote monitoring.
The digital image remote centralized monitoring system is a brand-new monitoring system, which breaks the limitations of the traditional CCTV monitoring system, can coordinate the needs of different equipment, ensure seamless communication, and solve the problems of video, audio, digital and other signals on the network. transmission. This emerging interactive multimedia monitoring system will gradually penetrate into all aspects of production and life. With the development and maturity of network technology, communication technology and VOD technology, it will be widely used.
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