Video server plays a role in monitoring
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What is network video surveillance? Network video surveillance is relative to analog surveillance and digital surveillance. In analog surveillance systems, image transmission, exchange, and storage are based on analog signal processing techniques. Digital monitoring introduces advanced digital signal processing technology and realizes digital storage represented by DVR. The network monitoring is based on digital signal processing, which realizes signal transmission, exchange, control, video storage and on-demand playback in a networked manner, and realizes all codec devices in the system by setting up a powerful central management platform (CMS). And unified management and centralized control of video storage devices. For the user, only need to log in to the central management platform to realize unified calling, browsing and management of the monitoring resources of the entire network. Network video surveillance implements end-to-end networking. The system architecture consists of IP front-end, TCP/IP network, central management platform, network storage device, TV wall decoder and client.
The video server can be divided into two categories: video encoder and video decoder. The video encoder is located at the front end of the network video surveillance system, while the video decoder is located at the user access end (or back end).
Video encoders are used to digitally compress and network front-end signals (video, audio, and other signals), including monitoring point analog video and audio information and access to alarm information, encoding/compression, transmission, and peripherals (such as cameras, Control of cloud mirrors, matrices, etc.). The above information is processed by the video encoder and uploaded to the central management platform through the IP network, and then distributed to the client, the video decoder, and the video storage device by the central management platform.
The biggest difference between video encoders and network cameras is that the video encoder's video source comes from analog cameras and needs to be used with analog cameras. The network cameras are integrated and integrate analog video capture. From the current situation, although network cameras are emerging in large numbers, video encoders will still occupy an irreplaceable important position in network video surveillance systems for the following two reasons: First, a large number of established analog and digital monitoring systems In order to protect the investment of existing analog cameras, these transformations will generate huge video encoder deployment requirements. Second, the selection of network cameras is far from being large, and it is difficult to meet the application of different users. Demand, so many applications must be based on the analog camera plus video encoder mode to achieve digital networking of the front end.
The video decoder is used to receive the network video monitoring code stream forwarded by the platform under the control of the PC client, and decode and output the analog signal to peripheral devices such as a video wall and an audio, and is usually deployed in the monitoring center of the user. The video decoder differs from the PC client in that the video decoder is generally based on hardware decoding, displaying the surveillance image through a dedicated display device, and the PC client directly displays the surveillance image through the PC display. Because PC clients have more control and management functions, and access is flexible and operational, applications based on PC clients for monitoring and browsing are becoming more and more popular. However, because the video decoder is based on hardware, the performance is stable and the image quality is good, so it is very common for many applications that need to centrally decode the upper wall.
Network video server key technology
ARM+DSP dual core architecture
The mainstream processing chips on the market, including TI's DaVinci series and HiSilicon's 3510 series, all use the dual-core architecture of ARM+DSP. In this architecture, ARM is the master processor of the chip, responsible for controlling the operation of each module of the chip and running the operating system, network protocol, application software, etc.; DSP system is mainly responsible for the processing of video and audio codec services, through the processor with video editing The decoding module performs the encoding and decoding of the audio and video together.
H.264 video compression algorithm
H.264 is a new digital video coding proposed by the Joint Video Team (JVT) jointly developed by ITU-T's VCEG (Video Coding Experts Group) and ISO/IEC MPEG (Moving Picture Coding Experts Group). Standard, which is both ITU-T H.264 and ISO/IEC Part 10 of MPEG-4. H.264 brings image compression technology to a higher stage and provides high-quality image transmission at a lower bandwidth. This advantage is very suitable for a large number of domestic operators and a relatively limited bandwidth of the access network/backbone network. . Under the same picture quality, H.264 saves 64% of the transmission stream compared to the previous generation encoding standard MPEG-2, and saves an average of 39% of the transmission stream compared to MPEG-4 ASP. The MPEG-4 encoding technology commonly used in China does not achieve the standard image quality under the bandwidth of 3 Mbps, and the H.264 encoding technology can provide the required image effect under the 2M bandwidth. Therefore, operators hope to introduce more advanced H.264 coding technology to further improve image quality with limited bandwidth resources.
With the continuous development of technology, more and more network video servers have already supported the H.264 compression algorithm, and H.264 is gradually replacing MPEG-4, becoming the mainstream algorithm in the security industry.
G.726 audio compression algorithm
G.726 is an audio coding algorithm defined by ITU-T. It was proposed in 1990 by CCITT (predecessor of ITU) based on the G.721 and G.723 standards. It has a higher compression ratio of 4:1.
Video server commonly seen problems
At present, most video surveillance systems have a big drawback: massive video data occupies expensive storage resources, and often the utilization of these video data is not high. The conventional practice is to arrange a special person to regularly watch the video troubleshooting problem, which is time-consuming and laborious, and it is difficult to achieve true "technical defense." Some companies such as MABTEX have pioneered the front-end network equipment supporting intelligent video analysis technology. Through computer vision technology and artificial intelligence technology, it can realize some very useful functions such as “virtual wallâ€, entry area detection, legacy object detection, and event detection. The security function can automatically identify the data that meets the preset characteristics in the massive video data and send it back to the management terminal, so that the entire video monitoring system is “slimmed downâ€, reducing the requirements on network bandwidth and terminal storage devices, and improving the system. Overall performance and reduced system cost.
At the same time, the application of network devices is increasingly limited by the network connection rate (bandwidth). When the video server is capable of transmitting images of HD above, the requirement for uplink bandwidth is about 1M. If a clearer image is to be transmitted, Ordinary ADSL transmissions are no longer sufficient. The video server with storage function introduced by some manufacturers such as D-LINK has solved this problem well. Through front-end storage, it can save the required high-definition video data in 7×24 hours without worrying about network congestion. Impact, through the support of USB, SD card, IDE / SATA hard drive, greatly enhance the competitiveness of the video server. Through the function of the terminal software, the new video server can also automatically select the video data stored in the front end when the network is idle. This user-friendly function setting greatly improves the existing one without adding any hardware equipment. The performance of the IP video surveillance system makes the advantages of the IP video surveillance system more traditional than the traditional analog surveillance system.
Under the bright prospect of the development of the security industry, industry players should also clearly understand some of the constraints that hinder the further development of video server vendors. The main points are as follows.
1. At present, the video server on the market has poor compatibility. In order to protect their own interests, various manufacturers adopt technical restrictions, and it is difficult for different brands of equipment to be used simultaneously in one system. In the long run, this is a limitation. The competitiveness of our own brand products.
2, the terminal software developed by various manufacturers, different functions, different methods of use, lack of professional training for customers, often make users confused, while the software interface is not standardized, the compatibility of various brands of equipment is almost zero, and even some manufacturers Even the SDK package is not provided, and secondary development is not supported. The barriers created in the software in this way make a lot of manpower and material resources in the actual project, and damage the interests of the customers.
3. Due to the large number of OEM products and illegal counterfeit products on the market, customers are hard to prevent. Hardware devices can be copied, and software can be copied. In order to prevent illegal soft copy, the original manufacturer often sets traps on the software. When the user selects the video server, it also chooses to buy the products that cannot be used, and bears huge risks.
4. Compared with other video surveillance products, video server products have high integration, complex composition and high hardware cost. When a fault occurs, they can only be returned to the factory for repair, the after-sales service cost is high, and the response speed is often not satisfactory to the customer. Businesses in each factory must strive to improve the new technology of video server, improve the technical support and related upgrade services for the original products, so that the end user satisfaction is the highest principle. This is the fundamental way for a product and a company to survive and develop. .
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