Comparison of Video Monitoring transmission modes

Video Monitoring has six transmission modes: Video baseband transmission, optical fiber transmission, network transmission, microwave transmission, twisted pair balanced transmission, and broadband co-cable transmission.

1. Video baseband transmission:

Is the most traditional television monitoring Transmission Mode, 0 ~ 6 MHz video baseband signals are directly transmitted through coaxial cables (non-balanced) without any processing. Its advantages are: low loss of image signal transmitted over short distances, and low cost. Disadvantages: the transmission distance is short, and the high-frequency components over 300 meters have a high attenuation, which cannot guarantee image quality. A cable must be provided for one video signal and a cable must be provided for the transmission control signal; its structure is a star structure with large wiring capacity, difficult maintenance, and poor scalability.

2. Optical Fiber Transmission:

Analog optical terminal and digital "> optical terminal> is the best solution for monitoring and transmission of dozens or even hundreds of kilometers of videos, by converting videos and control signals into optical signals for transmission in optical fibers. Its advantages are: long transmission distance, small attenuation, the best anti-interference performance, suitable for long-distance transmission. Its disadvantage is: it is not economical to transmit video monitoring signals within several kilometers; Optical fusion and maintenance require professional technical personnel and equipment operation and processing, and the maintenance technical requirements are high, and it is not easy to upgrade and expand.

3. network transmission:

It is a video monitoring transmission method that solves the problems of remote and extremely scattered locations between cities. It uses MPEG audio and video compression format to transmit video monitoring signals. The advantage is that the network video server is used as the video monitoring signal uploading device, and remote video monitoring software can be installed on the Internet for monitoring and control. Its disadvantage is that, due to network bandwidth and speed restrictions, only images with small images and low image quality can be transmitted; images with dozens or more frames can be transmitted per second, and the animation effect is very obvious and there is a delay, real-time Monitoring fails.

4. microwave transmission:

It is one of the solutions to solve the problem of video surveillance transmission in a location that is difficult to connect several kilometers or even dozens of kilometers. The image is carried to a high-frequency carrier and converted to a high-frequency electromagnetic wave for air transmission by means of FM modulation or AM modulation. The advantage is that it can dynamically transmit broadcast-level images in real time without the cost of wiring and cable maintenance. The disadvantage is that due to microwave transmission, L-band (1.0 ~ 2.0 GHz), S-band (2.0 ~ 3.0 GHz), Ku band (10 ~ 12 GHz), the transmission environment is open space, which is easily subject to external electromagnetic interference. microwave signals are transmitted in a straight line, and the middle is not blocked by mountains or buildings. Ku band is seriously affected by the weather, in particular, rain and snow may cause serious rain declines.

5. twisted pair wire transmission (balanced transmission ):

It is one of the solutions for the transmission of video surveillance images within 1Km and the complex electromagnetic environment. It processes the video surveillance image signals through balanced and symmetric Transmission. It has the following advantages: simple wiring, low cost, and high performance against common-mode interference. Its disadvantage is that it can only transmit video surveillance images within 1Km, and a twisted pair cable can only transmit one channel of images, which is not suitable for large and medium-sized video surveillance applications. Twisted Pair wires are weak in texture and have poor anti-aging capabilities, it is not suitable for field transmission. The high-frequency components of twisted pair wires have a large attenuation, and the image color will suffer a lot of losses.

6. Broadband common cable transmission:

It is the best solution for video monitoring signal transmission from several kilometers to dozens of kilometers. It adopts advanced technologies such as amplitude modulation, audio-frequency modulation, and PSK data signal modulation, it can integrate forty channels of video surveillance images, sound companion, control and alarm signals into a "one" coaxial cable for bidirectional transmission. The advantage is that it makes full use of the resource space of the coaxial cable, and provides bidirectional transmission of 40 audio/video channels and control signals in the same cable to realize "one-wire connection" of the broadband Common Cable. The construction is simple and easy to maintain, A large amount of material cost and construction cost are saved. The frequency division multiplexing technology solves the problem of Video Monitoring and transmission problems caused by scattered Distant Transmission points and difficult wiring. The RF transmission method only degrades the carrier signal, and the image signal attenuation is small, synchronous embedding of brightness and color transmission ensures that the image quality meets the national standards of more than 4.5. The 75 Ω coaxial unbalanced transmission gives it a very strong anti-interference capability, image Quality can still be ensured in complex electromagnetic environments. Its disadvantage is that it uses weak signal transmission, and the broadband modulation end requires an AC220V AC power supply. However, most video monitoring sites currently have this condition.

Based on the above transmission technologies, the wide-band common cable transmission mode should be used for video monitoring signal transmission within several kilometers or even dozens of kilometers, the broadband Common Cable Transmission Mode features simple wiring, flexible scalability, high cost performance, and high integration. It can integrate images, sound tracing, control, and alarm signals on the "one" cable, the video monitoring signal transmission mileage is achieved.

Appendix: Working Principle and composition of broadband Common Cable "one-line connection:

The bandwidth of the coaxial cable is 0 ~ 1000 MHz, while traditional video monitoring signals only occupy 0 ~ 6 MHz, bandwidth utilization less than 1%. Broadband refers to the modulation of multiple audio and video channels and control signals to different carriers to make full use of the coaxial cable resource space. The coaxial cable integrates audio and video and control signals modulated to different carriers into a coaxial cable for bidirectional transmission. Therefore, the "one-wire-to-one" two-way transmission platform for multi-system and multi-Signal Integration of a coaxial cable must be understood as a "one-wire-to-one" two-way transmission platform, the "one-line" television video monitoring and transmission system of a broadband common cable can be defined as a multi-channel integrated transmission of video surveillance images, sound companion and control signals, A "one-line-to-one" multi-function broadband Common Cable bidirectional transmission system that reserves alarm, broadcast, and other signal transmission space.

The principle and composition of the broadband Common Cable Video Monitoring System: consists of a video camera, a wide-band modulation device, a multi-channel video modem, and a Load balancer. The image signal is modulated to a high-frequency carrier by a wide-band modulation device, enables multi-channel signals to be transmitted upstream in the coaxial cable and transmitted to the main control room for single-channel or Multi-Channel Video modem to call up standard video signals; the front-end lens, cloud platform, and other control signals are modulated by the data carrier through the PSK data modulation, and modulated to the 38 MHz carrier over the coaxial cable for downlink transmission, the control signal is demodulated to the RS485 control mode and output to the decoder through a wide-band modulation to control the cloud mirror. This method achieves multi-channel monitoring signals "one-line communication". The technology used is mature, stable, and reliable, which greatly simplifies the wiring structure and cost.