A brief overview of the development stage of video surveillance systems

With the rapid development of technology, the video surveillance market has also developed rapidly. Video surveillance is widely used in many occasions due to its intuitive, convenient and rich information content. In recent years, with the widespread popularity of the Internet and the rapid development of computer, network, image processing, and transmission technologies, video surveillance technology has also made considerable progress. Video surveillance has penetrated into various fields such as education, government, entertainment venues, hospitals, hotels, sports venues, and urban security.

The video surveillance system has gone through three stages of development: local analog signal surveillance system, PC-based multimedia surveillance system, and Web server-based remote video surveillance system.

1. Local analog video surveillance

The local analog signal monitoring system is mainly composed of cameras, video matrices, monitors, video recorders, etc., using video transmission lines to connect the video from the camera to the monitor, using the video matrix host, using the keyboard to switch and control, video recording using tape Long-term video recorder; Long-distance image transmission adopts analog optical fiber, and uses optical transceiver to transmit video.

Before the early 1990s, the closed-circuit television monitoring system mainly based on analog equipment was called the first generation analog monitoring system. The image information is transmitted by analog cable using video cable. Generally, the transmission distance cannot be too far. It is mainly used for monitoring in a small area. The monitoring image can only be viewed in the control center.

The traditional analog CCTV monitoring system has many limitations:

(1) The transmission of wired analog video signals is very sensitive to distance;

(2) Wired analog video surveillance cannot be networked, and can only be used to monitor the site in a point-to-point manner, and makes the amount of wiring works extremely large;

(3) The storage of wired analog video signal data will consume a lot of storage media (such as video tapes), and it is very cumbersome to query and obtain evidence.

2. PC-based multimedia monitoring

In the mid-1990s, PC-based multimedia surveillance emerged with the development of digital video compression coding technology. The system has several cameras, various detection and alarm probes and data equipment at the far end, to obtain image information, and connect to the multimedia monitoring terminal through their respective transmission lines, and then pass the information to one or more through the communication network Monitoring centers. The monitoring terminal can be a PC or a dedicated industrial controller.

This type of monitoring system has strong functions and is convenient for on-site operation; but the stability is not good enough, the structure is complex, the video front end (such as CCD and other video signal collection, compression, communication) is more complicated, the reliability is not high; the power consumption is high, the cost is high ; Need to be on duty; at the same time, the openness of the software is not good, and the transmission distance is obviously limited. The PC also needs to be managed by a dedicated person, especially at a monitoring point where the environment or space is not suitable. This method is not ideal.

3. Remote Video Surveillance Based on Web Server

In the late 1990s, with the development of network technology, remote network video surveillance based on embedded Web server technology resulted in network video surveillance technology.

The main principle is that the video server has an embedded Web server and an embedded real-time operating system. The video information transmitted by sensors such as cameras is compressed by the high-efficiency compression chip and transmitted to the built-in Web server through the internal bus. Users on the network can directly view the image information on the Web server with a browser, and authorized users can also control the image acquisition method of the sensor. This type of system can be directly connected to the Ethernet, eliminating various complex cables, and has the characteristics of convenience, flexibility, plug and play, etc. At the same time, users do not need to use special software, just use a browser.

The network digital monitoring system based on embedded technology does not need to process the analog video signal PC, but converts the analog video signal output by the camera directly into an IP digital signal through the embedded video encoder. The embedded video encoder has powerful functions such as video encoding processing, network communication, and automatic control. It directly supports network video transmission and network management, making the monitoring range reach an unprecedented breadth. In addition to encoders, there are independent hardware modules such as embedded decoders, controllers, and video servers. They can be installed separately, and devices from different manufacturers can be interconnected.

The advantage of digital video surveillance is to overcome the limitations of analog CCTV surveillance:

(1) Digital video can transmit image data on a computer network (local area network or wide area network), which is basically not limited by distance, and the signal is not easily interfered, which can greatly improve image quality and stability;

(2) Digital video can be networked by computer network, and the network bandwidth can be reused without repeating wiring;

(3) Digital storage becomes possible. The compressed video data can be stored in the disk array or stored on the optical disc, and the query is very simple and fast.

From the previous analog surveillance to the current digital surveillance; from backward on-site surveillance to advanced remote surveillance; from manned surveillance to the current unattended surveillance, video surveillance is booming in the direction of digitization, networking and scale.

Of course, there are still many problems, such as: image quality issues, security issues, and service quality are topics that need further discussion. Compared with other IT businesses, the video surveillance business is relatively young, and there is currently no leader in the video surveillance market that can control the entire market. The above facts indicate that the video surveillance market will be a market with great development potential.