HD network cameras represent the future of surveillance cameras. The application of high-speed network transmission technology represented by optical transmission systems in my country is becoming more and more popular. Ultra-high-speed backbone networks spanning a large geographical range and high-speed networks in local areas have become normal facilities. It is possible, and there is still room for continuous reduction in tariffs. These have opened up a broad space for development of high-definition surveillance.
HD IP Cameras Matter
We know that traditional standard definition monitoring is divided into three types: analog, digital and network. The front end of analog surveillance is an analog camera, and the back end is a matrix. The front end of digital surveillance is also an analog camera, and the back end is a DVR. There are two front-ends for network monitoring, one is an analog camera video encoder, the other is a network camera, and the back-end is a platform. That is to say, in the era of standard definition surveillance, there are many types of front-end analog cameras, network cameras, video encoder analog cameras, etc.
The current high-definition video sensors are mainly CMOS, which directly output digital video signals. The digital high-definition video signals are directly compressed and encoded by DSP or ASIC in the camera, and then transmitted in a networked manner. It is economical, and the processing efficiency is higher.
While providing people with a clear visual experience, high-definition network cameras also put forward higher requirements for network bandwidth. To get large-scale applications, in addition to passively expecting network operators to make some adjustments, it is also necessary to take the initiative to take some alternatives to alleviate the contradiction of insufficient bandwidth for high-definition camera network transmission.
fiber optic transmission
1. Adopt advanced video compression standard
Actively adopt advanced video compression standards to ensure the best image quality with the least amount of data. At the same time, through the combination of image encoding technology and intelligent technology, the local encoding method can reduce the high-definition image transmission requirements to a considerable extent. network bandwidth.
At present, there are three mainstream compression formats, namely JPEG, MPEG-4, and H.264. JPEG is the compression of a single frame picture. The effect of a single picture is the best, but it occupies a large network bandwidth resource; MPEG-4 and H.264 are continuous compression between frames. Among them, the most popular compression format, H.264, has the highest compression efficiency. The video data compressed by H.264 requires less bandwidth during network transmission.
2. Provide dual stream support
While realizing high-definition local recording, the use of dual-stream technology can reduce the bandwidth usage of remote transmission and ensure better local image quality. In the remote monitoring environment, the HD camera can provide one high bit rate code stream for local high-definition storage, such as 720P/1080P encoding, and one low bit rate code stream for network transmission, such as QCIF/CIF encoding, taking into account both local storage and Remote network transmission. According to the network bandwidth, the stream format can be flexibly selected to achieve local high-definition storage, and at the same time, the back-end low-code stream network transmission. It can ensure the stable operation of the transmission system when the network resources available to users are limited.
3. Improve the added value of intelligent technology
Intelligent technology can improve monitoring efficiency, and the value it can bring is more than that. Through coding and intelligent analysis, the high-definition network camera with embedded intelligent analysis module can grab valuable information from the source and transmit it to the background. It can reduce the transmission pressure and truly achieve effective transmission. The high-definition camera itself can analyze and judge the collected images, and transmit the alarm signal to the back-end system, which is different from the previous intelligent technology that transmits the image to the back-end system and then analyzes the alarm by the software.
The previous method needs to occupy too much bandwidth and storage space, and due to the loss of image signals during the transmission process, false alarms are prone to occur. For HD cameras, because all signal processing is in the front camera, the signal is the most complete, so the accuracy of the alarm is greatly improved, and the bandwidth can be reduced at the same time.
4. Improve front-end caching technology
Design reasonable front-end caching technology to ensure that device images are not lost. The HD camera itself has limited data storage capacity and relies on communication transmission and back-end storage devices. We can prevent data loss in the event of communication failure by designing a reasonable front-end caching mechanism. For example, when designing a high-definition camera system, on-board memory or other storage devices are optional, and offline work is supported. In the case of abnormal network interruption, the data can be temporarily stored locally, and then sent back to the server when the network returns to normal. Network management technology can also be used to realize the front-end cache when the network is temporarily interrupted, and the video data will be automatically uploaded after the network is restored, thereby ensuring the integrity of the video.
5. Develop and comply with industry standards
It is necessary for all manufacturers in the monitoring market to unite and formulate some common norms, seeking common ground and reserving small differences. At present, the emergence of standardization organizations such as Onvif and PSIA makes people see the hope of standardization of video products and systems. The era of "plug and play" video surveillance is not far away.
Advantages of Fiber Optic Transmission
Network transmission has a popular promotion for monitoring, but it is also constrained by network bandwidth, and the transmission performance is stretched in large-scale long-distance projects. Based on the current basic megapixel HD 720P specification, the code stream is about 2 of D1. times, the bandwidth reaches about 4M, and when 1080P is used for calculation, the code stream is 5 times that of D1, and the bandwidth used is about 10M. Taking 100M Ethernet as an example, under the premise of ensuring smoothness, it can only carry about 5 high-definition images at the same time, but if multiple users access the same video source, the bandwidth occupied will be larger. Switching to Gigabit Ethernet can take dozens of channels. For small-scale high-definition monitoring systems, it can be effectively solved. For large projects, transmission performance will become a stumbling block.
In recent years, due to the rapid development of optical fiber communication technology, the cost of optical fiber transmission monitoring systems has also been greatly reduced, so the application of optical fibers and optical transceivers in monitoring systems has become more and more popular. As far as the author's investigation is concerned, it is found that optical fibers have been widely used in home optical fibers and office access networks, in the fields of home intelligence, office automation, industrial control networks, vehicle airborne and military communication networks. For high-definition video streams with high transmission bandwidth and transmission distance requirements, it is no longer a dream to realize high-definition monitoring with the advent of the optical fiber era.
From the perspective of development, due to the characteristics of optical fiber transmission, optical fiber is the preferred transmission medium for transmitting digital high-definition signals. Fiber optic transmission also offers the following advantages:
1. Wide frequency band, large amount of communication
The frequency band of optical fiber is very wide, theoretically up to 3 billion megahertz, which can ensure the transmission bandwidth and quality of digital high-definition signals. It is simply unmatched by traditional copper cables. This makes fiber optics an ideal underlying technology for high-bandwidth data transmission.
2. Low loss, suitable for long-distance transmission
Using traditional cables to transmit digital high-definition signals has an effective distance of only a few hundred meters, while using optical fibers can transmit hundreds of meters or even tens of kilometers. It is of particular significance for reducing the cost of high-definition signal communication and improving reliability and stability.
3. Anti-electromagnetic interference, no crosstalk interference, high confidentiality
Optical fiber is an insulator material, it is not disturbed by lightning interference in nature, changes in the ionosphere, and is not affected by electromagnetic fields and electromagnetic radiation, so optical fibers provide clearer signals than copper wires; it is difficult for light waves to be transmitted from the optical cable during the transmission process. leak out of the fiber. In this way, even if the total number of optical fibers in the optical cable is large, no crosstalk interference can be achieved, and outside the optical cable, the information transmitted in the optical fiber cannot be eavesdropped.
4. Light weight and small volume are convenient for construction and maintenance
Its tensile strength is good, its weight is small, and it is relatively small, so the optical cable can maximize the utilization rate of the wiring duct, and can reduce installation problems as much as possible. Through the following figures, we can analyze the advantages of optical fibers. 1000 twisted pairs with a length of 1 km weigh 8000 kg, while two fibers with a larger capacity of 1 km are only 100 kg in weight, which greatly reduces the need for maintenance. The need for expensive mechanical support systems, so fiber is better than copper.
5. Scalability
The system with optical fiber as the transmission medium has strong expansion ability. Because the optical fiber has a wide passband, chemical corrosion resistance, and long service life. After investing once to form a physical link, the system can be upgraded and expanded on the basis of the original link, only the equipment part needs to be replaced, and the original optical fiber network does not need to be replaced. Significant savings in system upgrade costs.
Optical fiber transmission technology provides unparalleled flexibility and scalability to meet future needs. Optical fiber can provide much higher bandwidth than copper wire, which makes it more and more used for the transmission of video signals, computer signals and high-definition signals. Optical fiber technology provides the best solution for high-definition video surveillance.
With the continuous improvement and development of monitoring technology, high-definition network cameras, as one of the main directions of monitoring technology development, combine optical imaging technology, intelligent analysis technology, network transmission technology, etc. to bring new changes, and continue to meet the needs of market competition. At the same time, it tends towards a perfect realization of the self. It profoundly affects the field of surveillance technology and will profoundly change our way of life.
