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Important Basic Knowledge of Network Video Surveillance System


1. What is network HD video surveillance?

The network video system usually refers to the IP monitoring system used for specific applications in the field of security monitoring and remote monitoring, which enables users to realize video monitoring and video image recording, and related Alarm management. Unlike analog video systems, network video systems use a network, rather than point-to-point analog video cables, to transmit video and other monitoring-related information.

2. What are the functions of the network high-definition video surveillance system?

The main functions of the network high-definition video surveillance system include remote image control, video recording, storage, playback, real-time voice, image broadcasting, alarm linkage, electronic map, PTZ control, data forwarding, photography, image recognition, etc.

3. What aspects can network high-definition video surveillance be applied to?

Mainly used in road monitoring, community monitoring, Internet cafe monitoring, safe city and other industries, has been applied to all walks of life.

4. What are the current mainstream network high-definition video surveillance products?

There are two kinds, network video server (DVS), network camera (IPCAM).

5. What is the difference between the network high-definition video surveillance system and the traditional video surveillance system?

Traditional closed-circuit monitoring systems (including DVR-based regional monitoring systems) use video cables or optical fibers to transmit analog video signals, which are very sensitive to distance, and long-distance transmission across regions is not economical and convenient (compared to network high-definition video monitoring). System - network high-definition video surveillance), generally centralized monitoring is carried out in a local area, and long-distance transmission is generally networked in a point-to-point manner. The wiring project of the entire system is large, complex in structure, high in power consumption, high in cost, and requires multiple people. On duty; the whole system management is less open and intelligent.

The network high-definition video surveillance system adopts a flexible rental method (mainly using IP broadband network), and multiple users can share a central control platform. can be viewed and controlled. It also introduces many new digital technology achievements (such as image recognition technology), which makes up for the deficiencies of traditional video surveillance systems, provides value-added business capabilities, expands functions and scope, and improves system performance and intelligence.

6. What are the advantages of network high-definition video surveillance system compared with analog closed-circuit system?

The information flow and media flow of the network high-definition video surveillance system are fully digitalized and independent of each other. The hardware and software adopt the design concept of standardization, modularization and scale. The configuration of the system equipment has strong versatility, good openness and flexible system configuration. , The control function is perfect, the data processing is convenient, the use is convenient, and the system installation, debugging and maintenance are simplified. At the same time, the scale of IP-based and digital products will bring cost advantages.

7. What functions can be realized by the network high-definition video surveillance system software platform?

The network high-definition video surveillance system platform can realize centralized monitoring management, video distribution, alarm linkage management, video storage management, system log management, remote video playback and viewing, etc.

8. How much does it cost to upgrade analog monitoring to digital monitoring?

The original analog monitoring system can be transformed by opening the access network line and installing video servers and other related equipment to realize the related functions of the network high-definition video monitoring system. In this case, the cost that the user needs to invest is the equipment investment, mainly the cost of the video server. Due to the different types and specifications of the video server, the specific cost should be negotiated with the local account manager.

9. How to deal with the original equipment when using the network high-definition video surveillance system? Does it not increase the cost of use?

The original equipment can be used for renovation, but related equipment such as video servers, access lines and network equipment need to be added. Recycling only involves a one-time cost and will not increase the daily cost of use.

10. Install the client software, or use a browser to access all the functions of the system?

There are two ways of using CS/BS, that is, you can use all the functions directly after installing the dedicated client or directly through the IE browser (need to download related plug-ins).

11. How does the network high-definition video surveillance system support alarm linkage and record at the same time?

Generally speaking, alarm linkage can be divided into front-end alarm linkage, platform alarm linkage, and client-side alarm linkage. After the alarm event is triggered, the alarm output device such as sound, light and electricity can directly output the alarm information at the front end and also trigger the alarm recording of the front end; after the platform receives the alarm information, it can trigger the platform's alarm linkage: send alarm short messages and customer emails, linkage Center video recording; after the client receives the alarm signal, it can immediately reflect it on the client interface to prompt the client that an alarm event occurs.

12. What are the ways to store video images in the network high-definition video surveillance system?

The network high-definition video surveillance system provides three storage modes: front-end, center, and client. The general principles for determining the storage location are as follows:

Front-end storage: If the user has high requirements for the real-time storage of images and the reliability of the front-end equipment can be guaranteed;

Central storage: If the front-end has no storage function, the central storage is generally used, and the central storage can be used as a backup for the front-end storage;

Client-side storage: generally used as temporary video image storage: such as snapshot, manual recording.

13. Do broadband users need to re-apply for a new line when adding a network high-definition video surveillance system? Can they use the existing physical line?

Under normal circumstances, the network high-definition video surveillance system can share the same access network line with other services. It is not necessary to apply for a new line to apply for a new network high-definition video surveillance system, and the network high-definition video monitoring system can be used by using the original line. However, if it turns out to be a dedicated line such as VPN, a specific analysis needs to be made according to the local networking situation, but from a purely technical point of view, as long as a certain resource allocation is added to the network, new users can still use the network HD without adding lines. Video surveillance system business.

14. What are the types of storage provided by the network high-definition video surveillance system?

The storage function of the network high-definition video surveillance system is divided into: front-end storage, central storage, and customer storage according to the characteristics of storage locations; front-end storage is to store video recordings in the hard disk that comes with the DVR; central storage stores video recordings in the central platform. In the hard disk array supported by the server or in the disk array supported by the network storage; the client-side storage stores video recordings in the disks in the client-side browsing monitoring machine.

15. What are the characteristics of the video surveillance industry's storage requirements?

Video surveillance has the following characteristics for storage requirements:

  1. The demand for storage capacity is relatively flexible. The amount of storage capacity is related to the requirements of picture quality, picture size, picture frame rate, storage time and other factors. Changes in these factors will cause great changes in storage capacity. .

  2. The performance requirements for storage are not high, but it needs to be able to meet long-term continuous data reading and writing, with large data traffic and a small number of simultaneous access requests.

  3. The data storage period varies in length, and can be reused after the use time is exceeded. General monitoring site data is stored for a certain period of time (eg 10 days), and can be deleted or overwritten later.

16. How to estimate the storage space size?

Choosing the right storage device for a video surveillance solution starts with estimating storage capacity requirements. According to the current mainstream compression method, the calculation is as follows:

H.264 compression method: D1 definition, real-time 25 frames, 500M/hour/channel;

H.264 compression method: HAFLD1 definition, real-time 25 frames, 300M/hour/channel;

H.264 compression method: CIF definition, real-time 25 frames, 200M/hour/channel.

17. What are the characteristics of data transmission of network high-definition video surveillance system?

The network high-definition video surveillance system has large data traffic and high real-time requirements. Generally, the size of a single channel of 25 frames/second CIF format image code stream is about 384Kbps; the size of a single channel of 25 frames/second DI format image code stream is 384-1500Kbps, and the average code stream is 900Kbps; The real-time and fluency requirements of the required images are different, and specific problems should be analyzed according to the actual situation.

18. How to carry out network broadband planning for network high-definition video surveillance system?

The network of the network high-definition video surveillance system can be divided into three parts according to the front end, the central service platform and the client:

1. Front-end bandwidth: estimate the required bandwidth; if a front-end only has one video server transmitting a DIF-image of 25 frames per second, the required bandwidth is 384kbps.

2. Platform: The broadband of the central service platform mainly consists of two parts, one part is the video stream uploaded by the front-end equipment; the other part is the video stream distributed by the central service platform to the client.

The broadband planning of the central service platform operated by the public network can be planned according to the scale of simultaneous monitoring and concurrency of 50% of the video of a platform's full-load front-end.

3. Client: The time needs to be determined by the number of video channels to be monitored. Since the bandwidth required for each video can be estimated, if a video server transmits a CIP image (still image) at 25 frames per second, the required bandwidth is about 384kbps (if the general motion of the image is considered, the code stream may be increased to 512kbps). If the number of channels monitored at the same time is n, the broadband planning on the client side is as follows: n*512 (kbps).

19. What are the requirements of the network high-definition video surveillance system for the transmission network performance?

The requirements for the transmission network in the technical specifications of the network high-definition video surveillance system are as follows:

The end-to-end communication quality requirements of the IP bearer network are as follows:

The upper limit of the packet loss rate of the bearer protocol The upper limit of the network delay

TCP 2/100 200ms

UDP 1/100 300ms

The "3111 General Technical Requirements" of the Ministry of Public Security stipulates that the network performance indicators within the monitoring center and the interconnection between monitoring centers meet the requirements of the communication industry standard YD/T1171-2001, and the content is as follows;

The quality (QoS) level requirements for the transmission network are as follows:

  1. The upper limit of network delay should be less than 400ms.

  2. The upper limit of delay jitter should be less than 50ms.

  3. The upper limit of the packet loss rate should be less than 1*10-3

20. What are the advantages and disadvantages of private line access?

Dedicated line access methods mainly include E1, SDH, ATM, FR, etc. The advantages of dedicated line access mainly include line stability, high bandwidth, and high security;

The main disadvantage is that the customer base is limited, and it is difficult for ordinary customers to accept the expensive price of the dedicated line.

21. What is multicast technology?

IP multicast (also called multicast or multicast) technology is a TCP/IP that allows one or more hosts (multicast sources) to send single data packets to multiple hosts (once, simultaneously). network technology. As a point-to-multipoint communication, multicast is one of the effective ways to save network bandwidth. In the application of network audio broadcasting, when it is necessary to transmit the signal of one node to multiple nodes, whether it adopts the repeated point-to-point communication method or the broadcasting method, the network bandwidth will be seriously wasted. Only multicast is the best choice. . Multicast enables one or more multicast sources to send data packets only to a specific multicast group, and only hosts that join the multicast group can receive the data packets. At present, IP multicast technology is widely used in network audio/video broadcasting, AOD/VOD, network video conferencing, multimedia distance education, "push" technology (such as stock quotes, etc.) and virtual reality games.

22. What is NAT technology?

The function of NAT (Network Address Translation) means that within a network, you can customize the IP address according to your needs without applying for it. Inside the network, each computer communicates through its internal IP address. When the internal computer wants to communicate with the external Internet network, the device with NAT function (such as: router) is responsible for converting its internal IP address into a legal IP address (ie, the applied Internet IP address) for communication.

23. Why is the video data generally transmitted using the UDP protocol?

TCP (Transmission Control Protocol) is a connection-based protocol. Before sending and receiving data formally, a reliable connection must be established with the other party. A TCP connection must go through three "conversations" to establish.

UDP (User Data Protocol, User Data Protocol) is a protocol corresponding to TCP. It is a non-connection-oriented protocol, it does not establish a connection with the other party, but directly sends the data packet.

From the above description, we can see that TCP is a connection-oriented reliable protocol, while UDP is a non-connection-oriented unreliable protocol. Compared with the transmission speed, the transmission speed of UDP is higher than that of TCP, which is more in line with network high-definition. Video surveillance systems have real-time requirements for data transmission.

24. What is the function of front-end equipment?

In the network high-definition video monitoring system, the front-end subsystem mainly realizes the collection of audio and video data, switch alarm data, audio and video coding and compression and network transmission of monitoring points. Front-end equipment mainly includes:

1. Image coding equipment (digital video recorder DVR, embedded video server, network camera);

2. Audio and video acquisition equipment (cameras, pickups);

3. PTZ/PTZ decoder;

4. Alarm input/output devices (switch value devices, alarms, etc.).

25. What is IP-CAMERA, video server, digital video recorder?


IP-CAMERA is a digital video device that integrates the functions of a video server and a camera; IP-CAMERA network cameras generally have digital cameras and recording devices with built-in Web services, and are directly connected to Ethernet (wired, wireless). Users can watch and listen to the video and sound transmitted from the IP camera through a standard Web browser.

2. Video Server (DVS)

Adopt digital compression algorithm to realize digital compression of audio and video information and network transmission and control equipment. The video server is generally an embedded video server device. It adopts the hardware design of embedded CPU, which is small in size and convenient in structure. Generally, there are 1-way, 2-way and 4-way audio and video input, and some can realize two-way intercom function. At present, some DVS devices can also have built-in small-capacity hard drives.

3. Digital Video Recorder (DVR)

DVR is Digital Video Recorder, digital video recorder or digital hard disk recorder, we are used to call it hard disk recorder. Combined with digital storage media with standard interface, digital compression algorithm is used to realize digital recording, monitoring and playback of audio and video information, and video equipment with system control function or video network transmission and monitoring equipment (generally with unique function control panel). At present, DVR products from South Korea and Taiwan occupy a high market share in the global market. There are PC industrial computer type and embedded type. In terms of high number of channels, there are more PCs and more embedded ones in low number of channels. South Korea is dominated by PCs, while Taiwan is dominated by low-channel embedded devices. There are also PC-type and embedded DVRs in mainland China. The previous DVR did not have the function of networking and was mainly based on local monitoring. According to the requirements of users and the development of technology, the DVR equipment of many manufacturers also has networking capabilities. According to the requirements of users, DVRs with networking capabilities generally view and store images in D1 format locally, and upload the images to the center. It is in CIF format. Generally, the DVR input does not exceed 16 channels. Try not to let the DVR work in the application of uninterrupted recording and network transmission at the same time.

26. Terminal equipment can be divided into:

1. IPC (integrated network camera)

2. DVS (video server without storage interface)


3. DVR (video server with storage interface)

Embedded PC architecture + board terminal equipment can be divided into:


27. How can the front-end equipment of the network high-definition video surveillance system avoid lightning strikes?

For the front-end equipment of the network high-definition video surveillance system installed outdoors, including video encoding equipment, cameras, PTZ and PTZ decoders, etc., the outdoor equipment must also comply with:

  1. The lightning protection grounding and safety protection design shall comply with the current national standards "Code for Design of Communication Grounding for Industrial Enterprises", "Code for Design of Lightning Protection for Buildings" and "30MHZ-1GHZ Cable Distribution System for Sound and TV Signals";

  2. Outdoor camera head lightning protection requirements: outdoor camera guns (with PTZ) need to install lightning protection devices (such as three-in-one DXS220AC or DXS24DC, including power supply, video interface, control signal lightning protection device) at the front end of the encoder, as Protection of outdoor front-end equipment;

  3. Video server: install 10f/BNC signal SPD on each video input port of video server; install 24DCP signal SPD on each signal control line; in areas with high lightning strikes, you can choose to install three-in-one lightning protection device as protection

28. How to install the front-end equipment of the network high-definition video surveillance system?

The installation of the front-end equipment of the network high-definition video surveillance system system needs to be treated according to different equipment. Before installation, carefully read the product manual and installation requirements. The standard procedure for installation of coded terminal equipment is as follows:

  1. Unpack to confirm the completeness of the equipment listed in the product description.

  2. Check the power supply voltage to prevent equipment damage due to voltage mismatches.

  3. Confirm whether the working environment of the device meets the environmental requirements for the device's working temperature and power supply in the product manual.

  4. Check the power-on test against the equipment manual to confirm that the various working status indicators can operate normally.

29. What is the difference between the client of the network high-definition video surveillance system and the monitoring center equipment?

The client of the network high-definition video surveillance system generally refers to the video display and composition of the user side from the perspective of system structure. The client of the network high-definition video surveillance system can be as simple as a computer that can access the Internet, or it can be as complex as a set of monitoring center subsystems, mainly including computers, monitors, large-screen controllers, storage devices, regulated power supplies, and network equipment. , video matrix, manual keyboard light composition.

30. How to control the large screen of the monitoring center equipment of the network high-definition video surveillance system?

Most of the high-end users need TV wall display for the monitoring center. In the monitoring center of the network high-definition video monitoring system, the digital signal is converted to the analog signal through the digital decoding matrix, and finally the selection of front-end equipment is switched to the TV wall.

31. How to install video server, PTZ and alarm equipment?

The function of the PTZ is to make the fixed camera rotate; and the alarm equipment generally plays the role of safety precaution. Once an abnormal situation occurs, the short circuit and open circuit signal of the electronic switch will be generated. After this signal is captured, the video server can generate a local alarm. The output signal can control various targets; such as remote linkage alarm, the alarm signal is remotely transmitted to the monitoring personnel, causing the personnel to warn the event and can make corresponding alarm processing according to the actual situation.

32. Classification and characteristics of cameras?

Cameras are roughly divided into the following categories according to their functions: bolts, dome cameras, integrated cameras, infrared day and night cameras, high-speed dome cameras, and network cameras.

  1. Bolt: It is cheap, but it does not have zoom and rotation functions, it can only monitor a fixed distance from one angle, and the concealment is poor;

  2. Dome camera: It has a certain degree of concealment, and at the same time, it has a small and beautiful appearance, and can be hoisted on the ceiling, making up for some of the shortcomings of the bolt;

  3. Integrated camera: built-in lens, can automatically focus, easy to control the lens, easy to install and debug;

  4. Infrared day and night dual-purpose camera: the camera, protective cover, infrared lamp, power supply and cooling unit are integrated into one camera equipment, which has the advantages of long night vision distance, strong concealment and stable performance;

  5. High-speed dome camera: a device that integrates an integrated camera and a pan/tilt, with features and functions such as fast tracking, 360° horizontal rotation, no surveillance blind spot and privacy area shielding;

  6. Network camera: also known as IP camera. It can digitally process and compress the image after it is captured, and send the compressed video signal to the server or client side through the IP network; on the server or client side, the remote image can be viewed in real time through the software.

33. What indicators should be paid attention to when choosing a camera?

1. Is the chip of the camera CCD or CMOS? At present, most surveillance cameras use CCD chips;

2. The size of CCD chip: At present, there are mainly 1 inch, 2/3 inch, 1/2 inch, 1/3 inch, 1/4 inch on the market, of which 1/3 inch and 1/4 inch CCD chips are mostly. The bigger the chip, the better the image quality and the more expensive the price;

3. Pixels of the CCD camera: the larger the pixel, the clearer the image;

4. Horizontal resolution of CCD: The resolution is represented by TV lines (referred to as tv lines). The typical resolution of color cameras is between 320 and 500 TV lines, mainly in different grades such as 330 lines, 380 lines, 420 lines, 460 lines, and 500 lines;

5. Lens: Calculate the focal length of the lens according to the object distance and imaging size, and select a suitable focal length lens such as standard lens, long focal length lens, and short focal length lens. At the same time, it is also necessary to consider that the imaging size of the lens should be consistent with the size of the camera CCD target surface. There are also factors such as lens resolution and aperture;

6. Minimum illumination: also known as sensitivity, is the sensitivity of the CCD to ambient light, or the darkest light required by the CCD for normal imaging. The unit of illuminance is lux (LUX). The smaller the value, the less light is needed and the more sensitive the camera is. High-sensitivity cameras such as moonlight and starlight can work in very dark conditions, and 1 to 3 lux is a general illuminance.

Moonlight type: The illumination required for normal work is about 0.1lux;

Starlight type: the illumination required for normal operation is below 0.01lux;

Infrared type: using infrared light for illumination, it can also image in the absence of light (black and white);

7. Signal-to-noise ratio: the typical value is 48db. If it is 50db, the image has a small amount of noise, but the image quality is good; if it is 60db, the image quality is good and no noise occurs;

8. Other factors: such as automatic gain and white balance.

34. How to choose an infrared camera?

Infrared cameras are mainly used in scenes where the target needs to be monitored day and night, especially when the target needs to be monitored at night, and the surrounding environment of the target does not have too much light. The specific selection is mainly based on the distance between the camera and the observation target. The distance range of a general infrared camera is 20-100 meters. The longer the distance, the more expensive the price and the higher the power consumption.

In addition, the switch control of the power supply of the infrared lamp should be considered when choosing an infrared camera. This problem can be controlled manually or automatically.

35. Under what circumstances does the network high-definition video surveillance system equipment need to consider integrated lightning protection equipment?

Strictly speaking, the monitoring system needs to install lightning protection equipment, whether it is indoor monitoring or outdoor monitoring. In general, the following lightning protection factors need to be considered:

1. Lightning protection of front-end equipment

Front-end equipment can be installed outdoors or indoors. Equipment installed indoors generally will not suffer from direct lightning strikes, but it is necessary to consider preventing the damage of lightning overvoltage to the equipment, while outdoor equipment should also consider preventing direct lightning strikes, such as front-end equipment. The camera should be placed within the effective protection range of the air-termination device (lightning rod or other air-termination conductor). In order to prevent electromagnetic induction, the power and signal lines leading to the camera along the pole should be shielded through metal pipes. The signal line has a long transmission distance and a low withstand voltage level. It is easy to induce lightning current and damage the equipment. In order to transmit the lightning current from the signal transmission line to the ground, the signal overvoltage protector must respond quickly, and the signal must be considered when designing the protection of the signal transmission line. parameters such as transmission rate, signal level, starting voltage, and lightning flux.

2. Lightning protection of transmission lines

The transmission line of the monitoring system is mainly the power line of the transmission signal line. The control signal transmission line and the alarm signal transmission line are generally made of copper-core shielded flexible wires, which are erected (or laid) between the front end and the terminal. From the perspective of lightning protection, the direct burial laying method has the best protection effect, and the overhead line is most likely to be struck by lightning, and it is destructive and has a wide range of influence. Grounding treatment, the suspension wire of the overhead cable and the metal pipes in the line should be grounded. The signal source and power supply at the input end of the intermediate amplifier should be connected to appropriate arresters respectively.

3. Lightning protection of terminal equipment

In the monitoring system, the lightning protection of the monitoring room is the most important, which should be carried out from the aspects of direct lightning protection, lightning wave intrusion, equipotential connection and surge protection. Since 80% of the high potential of lightning strikes is intruded from the power line, in order to ensure the safety of the equipment, the general power supply should be equipped with three-level lightning protection. Corresponding lightning protectors should be installed before the video transmission line, signal control line and intrusion alarm signal line enter the front-end equipment or before entering the central console.

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