Summary: high speed railway is different from the General railway system, high speed rail is a system, the integration of major projects, the only communication sector involves 10 multiple subsystems, including cable, data, transmission, dispatch, emergency communications, video surveillance, etc.
High-speed and conventional rail or subway difference is very large, such as Metro is usually about 60 kilometers per hour, the train was about 3 minutes interval while high speed can reach 300 km, time intervals may be more or less the same, this Metro on high-speed rail traffic control system make high demands, at the same time, as an important auxiliary facilities ...High speed railway is different from the General railway system, high speed rail is a system, the integration of major projects, the only communication sector involves 10 multiple subsystems, including cable, data, transmission, dispatch, emergency communications, video surveillance, etc.
High-speed and conventional rail or subway difference is very large, such as Metro is usually about 60 kilometers per hour, the train was about 3 minutes interval while high speed can reach 300 km, time intervals may be more or less the same, this Metro on high-speed rail traffic control system make high demands, at the same time, as an important secondary facilities, video monitoring system requirements corresponding very high.Features-iron and surveillance system
Iron's video surveillance system that requires the use of advanced video surveillance technology, based on the railway system of IP network, to build a digital, intelligent, distributed network video surveillance system, to meet the public security, safety, transportation, scheduling, operations, maintenance, public works, and signaling, vehicles, power supply, and other business departments and emergency prevention and monitoring, rescue and emergency management, and other needs, the implementation of video network resources and the sharing of information resources.
General high video monitoring system, based on network infrastructure for video capture, encoding, compression, storage, forwarding and virtual matrix functions. Camera capture to video signal through a coaxial cable to the DVR or encoder, video capture, encoding, compression and transmission, PTZ camera control signals are transmitted via RS485; encoders streaming video network to NVR for centralized storage backup; storage server can DVR or video information to NVR focused on backup; streaming media server to multiple users access a centralized video forward while reducing network and front-end equipment pressure; decoder and video wall connection, the video of large-screen display.Iron key technologies for video surveillance system
1. coding compression technology
Video encoding compression is network video monitoring of the prerequisite and basis, no compressed video data is huge.
At present the typical video encoding and compression standard is MPEG-4 H.264. MPEG's remains similar to the previous standard (H.261/3 and MPEG-1/2) of the basic encoding framework, which is typical of the third step: predictive coding, transform quantization and entropy coding. New coding standards are based on the optimization of the design, the previous standard of some technical improvements. For example, in the original Foundation on 1/4 and 1/8 pixel precision in motion compensation technology, making predictive coding performance greatly improved. MPEG is not a specific compression algorithm that is designed for digital television, interactive multimedia applications, video surveillance, and other integration needs of its compression technology. MPEG-4 combines multiple multimedia application integration in a complete frame, for different applications provided the corresponding categories (Profile) and level (Level). H.264, MPEG of the tenth part from ITU-T video coding experts group (VCEG) and ISO/IEC dynamic picture experts group (MPEG) combined joint video team (JVT, JointVideoTeam) high compression rate video coding standard. And the previous standard, the H.264 also use prediction coding and transform coding of mixed encoding modes, it has in the past, the advantages of various coding standard and incorporates standards development process experience for other encodings than ever better compression performance. H.264 standard maximum advantage is with very high data compression, in the same image quality conditions, the H.264 codec is MPEG-4 compression 1.5 ~ 2 times. H.264 uses "network friendly" structure and syntax, in favor of the BER and packet processing to meet the different rate, resolution, and different network transport, storage, occasion needs. As shown in Figure 1.Video encoding compression process diagram
In network video surveillance system, products between prepared mutual comprehension is very important, you can reduce the difficulty of integration, ease of expansion and cost of protection.
Currently, disparate vendors mutual series mutual solution is not satisfactory, i.e. compatibility is not good. The main reason is that different manufacturers use coding standards (profile) and level (level), another data encapsulation format is not compatible, then join the private information (in the Basic code stream/package).2. video analysis technology
Iron features a system span, geographic distribution, the environmental complex video analysis, wind, rain and snow and fog, camera jitter, the train of lights, city lights, insects, eliminating such phenomena are video analysis may encounter problems, good VCA system should be able to properly balance the false negatives and false positives.
Railway is different from the laboratory, the camera angle, focal distance of any such adjustments need to be human, material, video analysis on scenes (FOV) of demanding, in the future configuration of the need to constantly adjust it. Therefore, it is not difficult to understand most of the video surveillance system for video analysis is also used by the camera PTZ camera instead of a fixed camera. Analysis mode fixed, camera FOV adjust, you need to enter analysis settings, typically, the way the camera video can have only one mode.In railway applications, there are two main VCA mode, one is in important segments and throat area settings for intrusion detection, used to identify a person or animal intrusion into the high rail (iron fence along many semi-enclosed or physically protect, etc, but there is still a possible intrusion into); public cross-rail locale upper air analysis, prevention of falls from a height on the train. At present the two video analysis application mode in railway video monitoring in a certain application and good performance. As shown in Figure 2.Video analysis schema diagram
Current video analysis technology there are two primary ways that a schema is based on the back-end server, another way is to use front-end DSP (DVS or IPC).
DSP modes, i.e. the framework distributed intelligence analysis, video analysis unit General is located in the vicinity of the video capture device, so you can selectively set system to let the system occurred only when the alarm time transfer video to control centres or storage centres, relative to the server, you can save network burden and storage space. Video analysis is a complex process that need to consume large amounts of system resources, so the server can also make a video analysis of the way is very limited. For these reasons, the current market mainstream video analysis technology uses DSP modes, based on the camera or encoder. It is important to note that DSP based on the front-end of video analysis equipment, once the need to adjust the video analysis points, such as add or cancel video analysis function, you usually need to replace the DVS or IPC, based on the back-end analysis of patterns of the passenger or directly in the engine room control centre adjustment is complete, no need to replace the front end hardware. Typically replace DVS or IPC in railway project cost is very high.[1] [2]
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