This article refers to the address: http:// I. Introduction With the improvement of people's living standards and the rise of intelligent buildings, people pay more and more attention to the safety of their place of residence. In order to meet the safety requirements of modern buildings, people have developed some security monitoring systems, such as access control systems, video surveillance systems, card systems and so on. The technologies used are mainly digital audio processing technology, video processing technology and control information processing technology, and the three parts of processing and transmission are separated, which increases the overall cost of the product, especially the cost of construction installation and wiring. And it also brings great difficulty to the technical upgrade of the product. Here, we adopt network technology, and combine computer technology, automatic control technology and electronic technology to integrate these three parts into one whole, and use the network to transmit information to each user terminal and management terminal, thus realizing these subsystems. The unified control also greatly reduces the cost of construction, installation and wiring. Second, the composition of the system The intelligent video intercom monitoring system mainly consists of three parts: visual intercom part, access control card part and video monitoring. The video intercom part mainly provides a channel for identification and dialogue for visitors, user terminals and management terminals. The card part of the access control is set up for the convenience of the user. Especially when the user has multiple security systems, the card system will bring great convenience to the user. The video surveillance part is mainly used to monitor the situation around the user, including two parts, one is video surveillance of video intercom, and the other part is public places around the user such as corridors, elevators and other places to be monitored. The three parts are connected into a whole through a computer network to form a complete product. The whole computer network is composed of two completely independent networks, one is Ethernet, and the other is a half-duplex communication network based on 485 bus. Its structure is shown in Figure 1. 100Mbps Ethernet is mainly used to transmit real-time video stream data and control information and other information. The 485 bus-based communication network is used to connect the door terminal and the user terminal. Third, computer network technology The system uses two independent network systems, the first is based on the 485 bus half-duplex network system, and the second is based on the Ethernet LAN. The 485 bus half-duplex network system is used to connect door terminals, layerers and user terminals, which is mainly considered from the perspective of cost. Since these three parts exchange less information, the speed of data exchange is not very high and the implementation is relatively simple, so this network system is adopted. Communication uses a point-to-multipoint approach. The communication method is shown in Figure 2. A frame of information is sent by the door terminal to the layerer. After receiving the layerer, the called layerer distributes the information to all user terminals of the layer and waits for confirmation by the user terminal. After receiving the information, the called user terminal immediately sends an acknowledgement message to the layerer, and after receiving the layerer, sends a confirmation message to the door terminal. After the door terminal receives the confirmation from the layerer, the camera and the audio microphone are turned on, and the two parties can conduct a dialogue. The system uses a layerer to forward information frames in order to prevent overload when the number of users hooked up on the 485 bus is too large. The frame structure of the information consists of 5 bytes, the first byte records the layer information, the second byte records the user terminal number information, the third and fourth bytes are the checksum, and the fifth byte is The control flag is reserved in the first 3 bits of this byte, and the last 5 bits are the flag bits, namely the synchronization flag 1, the synchronization flag 2, the acknowledge flag 1, the acknowledge flag 2, and the error flag. The door terminal sets SYS1=1 while transmitting, and sets SYS2=1 when the layerer forwards. Similarly, when the user confirms, ACK=1 is set, and when the layerer confirms, ACK2=1 is set. When an error occurs, the system sets ERR=1 for the corresponding processing. The second network system is an Ethernet-based LAN, which mainly completes the communication function of the monitoring system, as shown in Figure 1. The system uses RTP protocol to encapsulate video data (using H.26 1 encoding), and uses H.22 5 recommendations to package and transmit these information streams (video streams and other control information streams), and use RTCP protocol to guarantee services. quality. Fourth, system hardware and software 1, system hardware Here we mainly give a more complicated door end terminal, the hardware composition principle shown in Figure 3. When the door terminal detects that a key is pressed, the button information is synthesized into a frame format and transmitted to the layerer via the 485 bus. At the same time, the camera of the door terminal is activated by the button of the door terminal, and the video signal is sampled and sent to the DSP chip for compression. The compressed video stream is packaged according to the RTP and H.225 protocols, and finally sent to the network through the Ethernet port. All layerers connected to the 485 bus will receive the signal from the door terminal, but only the called layer will process the received information and forward it to the corresponding user terminal after processing by the CPU. 2, software implementation There are two parts in the software design, one is the monitoring software of the monitoring terminal, and the other is the low-level software of each piece. The monitoring terminal adopts a multi-threaded software design method. The system uses a total of six threads for each monitoring point connected, namely, network monitoring thread, sending thread, receiving thread, H.26 3 image decoding display thread, image saving thread and Recording information (recording information such as dialing at the door end, accessing a card, etc.) detects the thread, as shown in FIG. The startup of the monitoring terminal thread is triggered by the door terminal. When the door terminal detects that the button is pressed, it immediately sends a broadcast command to the network; when the monitoring terminal listens to the broadcast message, starts the accepting thread, starts accepting the video data stream, and starts the display thread and the image saving thread accordingly. For the underlying software, mainly the control software of the door terminal, the workflow is shown in Figure 5. After the door terminal is powered on, the initialization work is performed first, and then the scan button and the card information are started. When the change is confirmed, the microprocessor CPU l first sends a frame information to the layerer and listens to the feedback information of the layerer. The startup DSP sends a broadcast message to the monitoring terminal through the network port, so as to start the receiving thread of the monitoring terminal to accept the video stream and the access information or card information. When the time exceeds 1 min or the termination key is pressed, the two parties terminate communication, and the CPU interrupt is triggered by the CPU 1 between the door terminal and the monitoring terminal to stop transmitting the video stream data. 4 Conclusion Cast Aluminum Heater,Die Casting Heater,Cast Barrel Heater Jiangsu Shazi Electric Equipment Co., Ltd. , http://www.cnhotpoint.com
Intelligent video intercom monitoring system is a high-tech product integrating computer technology, automatic control technology, network technology and electronic technology. It is an indispensable part of modern intelligent building construction. The system uses the network technology to connect the video intercom part, the video monitoring part and the access control card part into a complete product, which is debugged and runs well. Of course, the system has yet to be further improved and expanded, such as security systems, remote control, etc., the direction of future products will be more perfect, more intelligent and automation, such as automatic image recognition, more advanced wireless remote control, etc. .