Six ways of video surveillance transmission
[ Huaqiang Security Network News ] Security market has been very popular video surveillance, in the process of use, there are six transmission methods, but because of the variety of transmission methods, there are customers asked, so many transmission methods, which is better What? Let me analyze it one by one!
Video surveillance has six transmission modes: video baseband transmission, optical fiber transmission, network transmission, microwave transmission, twisted pair balanced transmission, and wideband common cable transmission.
1. Video baseband transmission is the most traditional TV monitoring transmission mode. It does not process any 0 to 6MHz video baseband signal, and directly transmits analog signals through coaxial cable (unbalanced). The advantages are: short-distance transmission image signal loss is small, and the cost is low. Disadvantages: short transmission distance, high frequency component attenuation of more than 300 meters, can not guarantee image quality; one cable should be equipped with one cable, and the transmission control signal needs another cable; its structure is star structure, large amount of wiring, maintenance Difficulties and poor scalability.
2. Optical fiber transmission is commonly used in analog optical transceivers and digital ">optical transceivers", which is the best solution to solve video surveillance transmissions of tens or even hundreds of kilometers, and converts video and control signals into optical signals for transmission in optical fibers. It is: long transmission distance, small attenuation, best anti-interference performance, suitable for long-distance transmission. Its shortcoming is: it is not economical for video surveillance signal transmission within several kilometers; optical welding and maintenance require professional technicians and equipment operation processing, maintenance technology High requirements, difficult to upgrade and expand.
3. Network transmission is a video surveillance transmission method that solves the long distance between the metropolitan areas and the extremely scattered points. The video surveillance signal is transmitted by the MPEG audio and video compression format. The advantage is that the network video server is used as the video monitoring signal uploading device, and the remote video monitoring software installed on the Internet network can monitor and control. The disadvantage is: limited by the bandwidth and speed of the network, only small images and low-quality images can be transmitted; only a few to a dozen frames per second can be transmitted, the animation effect is very obvious and there is delay, and real-time monitoring is impossible. .
4. Microwave transmission is one of the solutions to solve the video surveillance transmission of several kilometers or even dozens of kilometers. The method of frequency modulation or amplitude modulation is used to mount the image on a high frequency carrier and convert it into high frequency electromagnetic wave for transmission in the air. The advantages are: eliminating wiring and cable maintenance costs, and dynamically transmitting broadcast-level images in real time. The disadvantage is that due to the use of microwave transmission, the frequency band above 1 GHz is commonly used in L-band (1.0 to 2.0 GHz), S-band (2.0 to 3.0 GHz), and Ku-band (10 to 12 GHz). The transmission environment is open and easy. It is subject to external electromagnetic interference; the microwave signal is transmitted in a straight line, and there is no mountain or building blockage in the middle; the Ku band is more affected by the weather, especially in rain and snow.
5, twisted pair transmission (balanced transmission)
It is one of the solutions to solve the problem that the video surveillance image is transmitted within 1Km and the electromagnetic environment is complex. The video surveillance image signal processing is transmitted through balanced symmetry. The advantages are: simple wiring, low cost, and strong anti-common mode performance. The disadvantage is that it can only solve the video surveillance image transmission within 1Km, and one twisted pair can only transmit one image, which is not suitable for large and medium-sized video surveillance; the twisted pair texture is weak and resistant to aging, and is not suitable for field transmission. The high-frequency component of the twisted pair transmission is attenuated, and the color of the image is greatly lost.
6. Broadband common cable transmission is the best solution to solve the video surveillance signal transmission from several kilometers to tens of kilometers. It adopts advanced technologies such as amplitude modulation, audio frequency modulation and FSK data signal modulation, and can monitor video, sound and control of forty channels. And the alarm signal is integrated into the "one" coaxial cable for bidirectional transmission. The utility model has the advantages that: the resource space of the coaxial cable is fully utilized, and the forty-way audio, video and control signals are transmitted bidirectionally in the same cable, and the broadband common cable is “one-line communicationâ€; the construction is simple, the maintenance is convenient, and a large amount of material cost and construction cost are saved. Frequency division multiplexing technology solves the problem of remote transmission point dispersion, difficult video surveillance transmission; radio frequency transmission only attenuates the carrier signal, the image signal attenuation is small, and the brightness and chrominance transmission are synchronously nested to ensure the image quality reaches 4.5. The above national standards; 75Ω coaxial unbalanced transmission makes it very resistant to interference, and the image quality can still be guaranteed in complex electromagnetic environments. The shortcoming is: using weak signal transmission, the AC220V AC power supply is required for the wide-band modulation end, but most video surveillance points currently have this condition.
Combining the above several transmission technologies, it is necessary to solve the transmission of video surveillance signals within a few kilometers or even tens of kilometers. Broadband common cable transmission mode is adopted. The broadband common cable transmission mode has simple wiring, flexible expansion, high cost performance, strong integration, and can integrate images and sounds. The control and alarm signals are “one†cable, which realizes the mileage crossing of video surveillance signal transmission.
Attached: The working principle and composition of the broadband common cable "first line":
The so-called broadband is relative to the traditional video surveillance using video baseband transmission, the bandwidth of the coaxial cable is 0 ~ 1000MHz, while the traditional video surveillance signal only occupies 0 ~ 6MHz, bandwidth utilization is less than 1%. Broadband refers to the modulation of multi-channel audio, video and control signals onto different carriers in order to make full use of the coaxial cable resource space. The common cable is to integrate audio and video and control signals modulated to different carriers into a coaxial cable for two-way transmission. Therefore, the wide-band common cable "one-line communication" should be understood as a "one-line" two-way transmission platform for multi-system, multi-signal integration of a coaxial cable transmission, and a wide-band common cable "one-line communication" TV video surveillance transmission system can be defined as multi-channel The video surveillance image, audio and control signals are integrated and transmitted, and the "one-line" multi-function broadband common cable two-way transmission system for alarm and broadcast signal transmission space is reserved.
Broadband common cable video surveillance system principle and composition: mainly consists of camera + broadband modulator + multi-channel video demodulator + FSK data modulator, etc., through the broadband modulator to modulate the image signal to the high-frequency carrier, so that multiple signals can be Uplink transmission in the coaxial cable, transmission to the main control room through a single or multiple video demodulator to demodulate the standard video signal; control signals for the front lens, pan/tilt, etc. through the FSK data modulator for data carrier modulation, modulation Down to the 38MHz carrier through the coaxial cable downlink transmission, the control signal is demodulated into the RS485 control mode output to the decoder through the broadband modulator, thus achieving the control of the cloud mirror. In this way, the multi-channel monitoring signal "one-line communication" is realized, and the adopted technology is mature and reliable, and the wiring structure and cost are greatly simplified.
Video surveillance has six transmission modes: video baseband transmission, optical fiber transmission, network transmission, microwave transmission, twisted pair balanced transmission, and wideband common cable transmission.
2. Optical fiber transmission is commonly used in analog optical transceivers and digital ">optical transceivers", which is the best solution to solve video surveillance transmissions of tens or even hundreds of kilometers, and converts video and control signals into optical signals for transmission in optical fibers. It is: long transmission distance, small attenuation, best anti-interference performance, suitable for long-distance transmission. Its shortcoming is: it is not economical for video surveillance signal transmission within several kilometers; optical welding and maintenance require professional technicians and equipment operation processing, maintenance technology High requirements, difficult to upgrade and expand.
3. Network transmission is a video surveillance transmission method that solves the long distance between the metropolitan areas and the extremely scattered points. The video surveillance signal is transmitted by the MPEG audio and video compression format. The advantage is that the network video server is used as the video monitoring signal uploading device, and the remote video monitoring software installed on the Internet network can monitor and control. The disadvantage is: limited by the bandwidth and speed of the network, only small images and low-quality images can be transmitted; only a few to a dozen frames per second can be transmitted, the animation effect is very obvious and there is delay, and real-time monitoring is impossible. .
4. Microwave transmission is one of the solutions to solve the video surveillance transmission of several kilometers or even dozens of kilometers. The method of frequency modulation or amplitude modulation is used to mount the image on a high frequency carrier and convert it into high frequency electromagnetic wave for transmission in the air. The advantages are: eliminating wiring and cable maintenance costs, and dynamically transmitting broadcast-level images in real time. The disadvantage is that due to the use of microwave transmission, the frequency band above 1 GHz is commonly used in L-band (1.0 to 2.0 GHz), S-band (2.0 to 3.0 GHz), and Ku-band (10 to 12 GHz). The transmission environment is open and easy. It is subject to external electromagnetic interference; the microwave signal is transmitted in a straight line, and there is no mountain or building blockage in the middle; the Ku band is more affected by the weather, especially in rain and snow.
5, twisted pair transmission (balanced transmission)
It is one of the solutions to solve the problem that the video surveillance image is transmitted within 1Km and the electromagnetic environment is complex. The video surveillance image signal processing is transmitted through balanced symmetry. The advantages are: simple wiring, low cost, and strong anti-common mode performance. The disadvantage is that it can only solve the video surveillance image transmission within 1Km, and one twisted pair can only transmit one image, which is not suitable for large and medium-sized video surveillance; the twisted pair texture is weak and resistant to aging, and is not suitable for field transmission. The high-frequency component of the twisted pair transmission is attenuated, and the color of the image is greatly lost.
6. Broadband common cable transmission is the best solution to solve the video surveillance signal transmission from several kilometers to tens of kilometers. It adopts advanced technologies such as amplitude modulation, audio frequency modulation and FSK data signal modulation, and can monitor video, sound and control of forty channels. And the alarm signal is integrated into the "one" coaxial cable for bidirectional transmission. The utility model has the advantages that: the resource space of the coaxial cable is fully utilized, and the forty-way audio, video and control signals are transmitted bidirectionally in the same cable, and the broadband common cable is “one-line communicationâ€; the construction is simple, the maintenance is convenient, and a large amount of material cost and construction cost are saved. Frequency division multiplexing technology solves the problem of remote transmission point dispersion, difficult video surveillance transmission; radio frequency transmission only attenuates the carrier signal, the image signal attenuation is small, and the brightness and chrominance transmission are synchronously nested to ensure the image quality reaches 4.5. The above national standards; 75Ω coaxial unbalanced transmission makes it very resistant to interference, and the image quality can still be guaranteed in complex electromagnetic environments. The shortcoming is: using weak signal transmission, the AC220V AC power supply is required for the wide-band modulation end, but most video surveillance points currently have this condition.
Combining the above several transmission technologies, it is necessary to solve the transmission of video surveillance signals within a few kilometers or even tens of kilometers. Broadband common cable transmission mode is adopted. The broadband common cable transmission mode has simple wiring, flexible expansion, high cost performance, strong integration, and can integrate images and sounds. The control and alarm signals are “one†cable, which realizes the mileage crossing of video surveillance signal transmission.
Attached: The working principle and composition of the broadband common cable "first line":
The so-called broadband is relative to the traditional video surveillance using video baseband transmission, the bandwidth of the coaxial cable is 0 ~ 1000MHz, while the traditional video surveillance signal only occupies 0 ~ 6MHz, bandwidth utilization is less than 1%. Broadband refers to the modulation of multi-channel audio, video and control signals onto different carriers in order to make full use of the coaxial cable resource space. The common cable is to integrate audio and video and control signals modulated to different carriers into a coaxial cable for two-way transmission. Therefore, the wide-band common cable "one-line communication" should be understood as a "one-line" two-way transmission platform for multi-system, multi-signal integration of a coaxial cable transmission, and a wide-band common cable "one-line communication" TV video surveillance transmission system can be defined as multi-channel The video surveillance image, audio and control signals are integrated and transmitted, and the "one-line" multi-function broadband common cable two-way transmission system for alarm and broadcast signal transmission space is reserved.
Broadband common cable video surveillance system principle and composition: mainly consists of camera + broadband modulator + multi-channel video demodulator + FSK data modulator, etc., through the broadband modulator to modulate the image signal to the high-frequency carrier, so that multiple signals can be Uplink transmission in the coaxial cable, transmission to the main control room through a single or multiple video demodulator to demodulate the standard video signal; control signals for the front lens, pan/tilt, etc. through the FSK data modulator for data carrier modulation, modulation Down to the 38MHz carrier through the coaxial cable downlink transmission, the control signal is demodulated into the RS485 control mode output to the decoder through the broadband modulator, thus achieving the control of the cloud mirror. In this way, the multi-channel monitoring signal "one-line communication" is realized, and the adopted technology is mature and reliable, and the wiring structure and cost are greatly simplified.
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