In the field of subways, the construction of typical security systems is divided into different systems. Video and alarms, and access control belong to different systems, although their integration in relatively large systems is relatively high. However, security-integrated linkage based on video, access control, and alarms appears to be weak and cannot fully exploit the advantages of security integration. What is the trend of subway security as the highlight of the security field in the future? HD? Or smart?

At present, there are 36 cities in China reporting to the national competent authorities; the urban rail transit construction and development plan, of which 28 cities have been approved, these 28 cities plan to build 96 rail transit lines by 2015, with a total length of over 2,500 km. The total investment exceeds 1 trillion yuan.

Subway Security Creates a Major Role in Security

Subway security is already one of the most important systems for cities other than domestic and foreign cities except for signal systems. If we simply estimate from the traditional weak security systems such as CCTV and access control systems, the scale of more than 20 domestic cities will be built, and each city will have The traditional security system of the line is approximately 100 million, and each city is calculated on 6 lines, totaling more than 12 billion yuan. As a result, subway security is the highlight of the security industry.

The proportion of subway construction and operating costs is not very high, but when extreme events are encountered, the role played is decisive. The security industry, as an emerging industry with great growth in the national economy, is rapidly developing. The demand for security products in various industries is also increasing. It is reported that 33 cities in China are planning to construct subways and 28 cities have been approved. Subway security will become another hot spot in the security industry.

The rapid development of subway construction has brought new development opportunities to security companies. The explosion of the London Underground in 2005 was a wake-up call to the global rail transit industry. The importance and investment of railroad security in the country are on the rise. The proportion of video systems in rail transit has increased. “From the perspective of subway safety threats, the possibility of an explosion happening in China is very small. However, the high concentration of people in the subway, especially during peak hours, poses a potential risk. The occurrence of a small situation may cause people to Panic has caused people to flee blindly, resulting in crowded and even stampede events. Therefore, security systems are needed to do more work on passenger flow control, warning and crisis management.” Chief Engineer Office, Construction Headquarters, Guangzhou Metro Corporation Engineer Chen Gang pointed out.

The field of subway security mainly includes video surveillance systems, access control systems, anti-theft alarm systems and intelligent video analysis. As a real-time image verification and historical image query tool, the video surveillance system is the most important and most important part, occupying 70%-80% of the total, and the access control system is mainly for the internal management of subway users, accounting for about 10%-20%. The alarm system is relatively small. From the perspective of future investment, security and explosive detection and flammable/toxic gas detection will gain greater application in rail transit. Divided from the application requirements, the subway video image is divided into two parts, one part is the video surveillance system for operational services, mainly for the control center, depots, stations and operations; the other part is the public security video surveillance system for public security services, to realize the city Bureau, Metro branch, police station and police room monitoring.

The subway operates in a relatively narrow and confined underground space. It is crowded and vulnerable to attack and destruction. With the increasing demand for the construction of subway video surveillance, the number of surveillance cameras has doubled, and it is difficult to realize that it is difficult to realize because of the active surveillance of the attendants. Intelligence is a constant demand. At present, subway safety management has evolved from a passive post-recovery type to a more proactive, predictive safety management method. The use of intelligent video analytics technology to achieve early warning and prevention of demand is evident. The development of security technology is very rapid. Security of subways is at a stage of development. There should be more new technologies and new manufacturers, be inclusive and open minded.

Subway Security Four Development Trends

1, high-definition

Due to the special nature of high-speed railway operation, the construction of the security system at this stage is divided into two major systems in most subways: access control and alarms belong to integrated monitoring, and video surveillance belongs to communication systems. Both are based on the network to achieve functional integration and unified management. It is required that the security system must also provide corresponding network solutions.

In the actual application, the digital solution for video surveillance has not been applied due to the limitations of the technology. At present, the typical approach is a digital-to-analog solution that combines matrix control with MPEG-2 and MPEG-4 dual-stream technology. As shown in Figure 1, the front-end camera analog signal is distributed through the signal, all the way into the local analog matrix, real-time local control and monitoring through the joystick keyboard; all the way into the MPEG-2 encoder, through the subway internal network, transmission to the monitoring center After the decoder decodes, it monitors the large-screen display and can control it; the third way enters the MPEG-4 encoder to achieve real-time storage.

In general, each station will set up a simulation matrix and use the joystick keyboard to monitor all the images in the station. In the subway system, the camera at each station is not particularly large. In this case, using the joystick keyboard can quickly control the matrix and switch the image.

In the existing system, the compression methods of MPEG-2 and MPEG-4 are considered respectively for the transmission and storage of video: To achieve the quality of the image in the center of the large-screen browsing in the control center, the MPEG-2 encoding method is adopted for transmission. ; And MPEG-2 compressed code stream is usually greater than 10mb/s, when real-time storage, the storage space required by the system will be very large, will greatly increase investment costs, so consider the use of MPEG-4 encoding (in D1, 25 frames In the case of /sec, the bitstream is about 2mb/s) to solve the storage space problem required for real-time storage.

2, coding technology optimization

It is worth noting that the choice of video coding technology has a huge impact on the design and construction cost of urban rail transit digital video security architectures. At the same time, MPEG-2 and MPEG-4 compression methods are used to solve the problem of image quality and storage space. The contradictory issue is a huge waste of investment. With the development of codec technology, especially the application of scalable coding technology, the contradiction between image quality and bandwidth is resolved. If scalable coding technology is chosen, the work previously required to be performed by the MPEG-2 and MPEG-4 dual coding methods now requires a single algorithm to be perfectly implemented to H. The coding standard represented by 264-SVC is a concrete expression of the application of scalable coding technology. Specifically, scalable coding technology has the following advantages:

First, the scalable encoding technology only provides a unique stream: This stream can be flexible to meet the needs of different devices and networks, rather than coding multiple formats for each video source.

Second, it supports the expansion of time, space, and image quality: this means that a standard PC can be used for decoding in multiple ways to meet the needs of devices with different processing capabilities. Multiple users can simultaneously share the same video. Decode with different resolutions.

Third, the multi-resolution function makes it possible to configure different resolutions (spatial and temporal) on one port, and different resolutions and frames can be selected as sub-resolutions and frames for each physical video port. . Spatial scalability means that for the same image source, pictures with different resolutions (D1, CIF, and QCIF) can be obtained in the same time; the scalability on the time axis means the frame rate during playback. Adjustability; In addition, H. The 264-SVC image compression technology also supports the tunability of image quality, and the same video stream can be set with different image quality for viewing or storage.

Fourth, the use of scalable compression technology applied to urban rail transit can also be a good solution to the problem of on-board monitoring. At present, because the wireless bandwidth can not meet the requirements of video transmission, the on-board monitoring system is mostly an independent system. The video information is transmitted to the driver's office in real time for monitoring and local storage. After the train arrives at the station, it is manually transferred. However, if a compression technology with scalable characteristics is adopted, appropriate transmission resolution and frame number can be selected according to requirements, and the wireless real-time transmission requirements of the image can be achieved, thereby forming a complete unified platform with the station monitoring system.

In addition, for a long time, the video surveillance system in subway security has always had both operational and security requirements. Due to different concerns and different management requirements, it is usually established two independent systems that do not interfere with each other and manage independently. However, if a networked, digital video/software solution is adopted, the system can be easily expanded and the authority and priority of control can be determined according to the different management needs of the operation and public security so that both the operation and public security can share resources. At the same time, it does not affect each other and reduces the problem of repeated investment to a great extent.

3, intelligent

With the development of technology, the requirements for intelligentization of subway security systems are also increasing. We hope that the previous passive security will be gradually transformed into active security, thus greatly reducing the demand for personnel and their work intensity. Video intelligent analysis applications are typical Performance.

At present, subway security construction basically puts forward the demand for intelligent video analysis, but there are not many applications in a wide range. The main reasons are: many intelligent video analysis functions have higher requirements for the application environment, and the false alarm rate is usually Can not reach the actual application needs. Therefore, it must be based on the current level of smart video analysis technology, combined with the actual application of the subway in order to achieve satisfactory results.

From the current point of view, some technologies of intelligent video analysis can already be applied in practice, for example, smart detection functions for camera status, camera black frame detection, camera overexposure, lens blocking, image blur, camera shift, etc. These technologies are relatively mature and can achieve satisfactory results in most cases. In addition, some of the more complex functions, such as the qualitative inspection of station traffic and the detection of personnel crossing the line, are themselves in line with the management needs of the subway. Combined with the on-site situation, they can also achieve corresponding intelligent detection results, but they are relatively complicated. Applications should be more careful and rigorous. Applying intelligent video analysis technology to the subway security system, combined with the application of the video management platform, can greatly increase the intelligence of the security system.

4, security integration

Metro security demands very high integration of the system, especially the integrated monitoring system. In fact, the systems related to subway security are not just video, access control, and alarms. The relevant systems such as equipment monitoring systems, fire alarm systems, data transmission platforms, and information broadcast systems should all be part of the security system. With the increasing emphasis on security by users, the integration of the overall security system has become a trend that has also been applied in some subway projects. Moreover, it is precisely because the subway security system integration involves many subsystems. Therefore, only when the systems are coordinated, deep integration can meet the requirements of rail transit development on the security system.

As an artery of urban traffic, the subway has shortened the distance between time and space, and has become an important means of transportation for many major cities to alleviate traffic congestion. In recent years, the demand for comprehensive subway security systems has greatly boosted its domestic development. However, we have noticed that the other side of demand is the amount of supply, which is precisely the "cartilage" of China's security companies. There is no end to safety construction! How to control the investment cost of the subway comprehensive security system, make it more energy-efficient, improve the overall system operation and maintenance management, and enhance the quality of subway services in all directions will all be worth exploring and pondering.