With development of network technology and computer technology, application of IP network has been widely popularized based on TCP/IP protocol.Construction of high speed backbone network and development of regional high speed access system has accelerated various video communication applications based on IP technology.The digital video monitoring based on TCP/IP network has been very popular solution in recent years. It conforms to the time tide of network and IP with high technical content.The most important feature is the unlimited transmission distance which can be conveniently connected with other systems. It makes video recording and accident investigation very convenient. In addition, it can conveniently give access to other security devices like alarm for temperature, moisture, smoke detector and invading. meanwhile, it can be connected with action devices like light, warning signal and lock. This makes it easy to form a set powerful security system.

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The main principle is adopting embedded real time multi task operation system and integrating video compressing and transmission function in the chip. After digitalization, the video signal transmitted from the camera will be compressed by the high efficiency compressing chip then transmitted to the network or server through internal processing.The network user can view the monitoring image using special software or the browser. The authorized user can even control action of pan-tilt  lens of the camera or configure the system.The main feature of the monitoring system is to integrate the function of video compressing and uploading into a device of small dimension. It can get direct access to Ethernet or Wide Area Network which achieves plug to see. It has saved different complex cables for convenient installation (only 1 IP address needed).The main devices of the digital video monitoring system based on TCP/IP network are network camera, management server and storage server.

Network Camera:

Network camera is the digital camera equipment which has integrated advanced technologies including video compressing technology, computer technology, network technology and embedded technology, etc.It mainly includes devices like lens, optical filter, image filter, video compressing card, network card and storage unit, etc.Main features as following:

(1) Adopting embedded system, it can work independently without aid from computer.

(2) With independent IP address, directly connect with Ethernet through LAN, DSL or wire network adopter.

(3) Support a variety of network communication protocol such TCP/CP. The LAN user or Internet user can use standard network browser to visit network camera according to IP address.

(4) Able to view real time image transmitted through network.

(5) Monitor the object omnidirectionally by controlling the lens and plat-tilt.

(6) The advanced network camera has other attractive functions such as motion detection, email alarm and FTP warning, etc.

(7) Adopt MPEG4 and H.264 video compressing technology to primarily solve the sharp contradiction between image digitalization and broadband. The feature of the algorithm is that it achieves the high compressing percentage of high quality video image. Compared with DVD image quality, its compressing percentage has been increased by 3 to 5 times.  

Networked Storage:

Considering the development trend of networking of video monitoring system, the network storage will play a more important role in the future video monitoring system.The network video monitoring system raises 2 requirements for storage: the first is networking of deployment and visit.Considering the proper distribution of traffic and storage space, the deployment position of the storage device in the system will be tending to front end and distribution.For the users' convenience to visit, all storage space in the system should be transparent. The user needs only one interface to visit all storage resource. the second is the networking of the storage device. The network video monitoring system is quite suitable for large scale monitoring networking application. In order to meet requirement for mass concentrated storage, the storage device need adopt advanced network storage technology to ensure flexibility of space expansion.

Front End Storage:

The front end storage is to inlay storage components in the front end device of network video monitoring system (such as network camera). complete local recording and storage of monitoring image from the front end device directly.The front end storage has several advantages: firstly, reduce capacity pressure brought by concentrated storage through distributed storage deployment. secondly, effectively relieve the network traffic pressure brought by concentrated storage. thirdly, avoid loss of image of concentrated storage when network breaks down.CF card or SD card are usually adopted by the network camera for the front end storage because single front end encoding device monitor less lines with less storage time, which requires less storage capacity.To ensure the flexibility and convenience of users' visit, all front end storage of the network video monitoring system should not only provide point-to-point single access, should also provide concentrated sharing of all content through an unified interface.Therefore, the network video monitoring system unifiedly manage and dispatch all front end storage through central business platform and achieve networking of storage space and storage content.By this way, the user can not only login to single front end device to request replaying of the video image , can also login to central business platform to intensively search and replay all front end video images.   

Sub Central/Center Storage:

In the network video monitoring system, what is often deployed is the sub center storage.The front end device collects the images from the monitoring points, encode and compress them into digital monitoring code steam, then transmit them to central business platform through network. The central business platform will  distribute the code stream to the monitoring center for concentrated storage.In a lot of large scale video monitoring systems, distributed central storage has been adopted, namely, sub central/central storage.In this way, on one hand, it can reduce the pressure of storage capacity and network traffic brought by one central concentrated storage, on the other hand, it can greatly improve reliability of the system.Using central/sub central storage has following advantages: firstly, it will be more convenient for the user to search and call the video image. secondly, It's much easier to ensure completeness of the storage content. It won't cause loss of important content due to theft loss or damage of any front end device. thirdly, the resource can be properly dispatched to distribute storage space according to the demand in order to save resource. fourthly, it's good to make various storage strategies to meet users' personalized requirement. fifthly, easy to maintain and convenient for integrated checking and fault shooting in time.Currently SAN (storage regional network), NAS (network visit storage) and iSCSI are the relatively advanced network storage equipment and storage technology.SAN is based on fiber channel technology. The server and the storage array are connected by fire channel switch to form regional network exclusively used for data storage.SAN has adopted network -oriented storage structure, data processing and data storage separation with features such as easy expansion, flexible addressing, long distance transmission, high I/O performance, high use ratio of storage device etc. This is a brand new storage system structure.NAS achieves the interconnection between the server and the storage array based on IP network. It uses TCP/IP protocol for communication and file level I/O for data transmission.By comparison, installation, debugging, using and management of NAS equipment are more simple with low deployment cost.iSCSI is  a new IETF protocol. It is a kind of transmission standard to convert SCSI block data into network packet through IP network.Same as NAS, it transmit the data through IP network. But in terms of data access, it adopts Block Protocol which is same as SAN but different from NAS.Therefore, the values iSCSI brings to the user are: firstly, iSCSI makes it possible for data package to be transmitted in Ethernet. for SAN it can achieve its original functions through IP network instead of expensive fiber network. It reduces management complexity and also the cost. secondly, due to complexity of uses' application demand, usually both SAN and NAS are deployed. however, iSCSI is able to integrate both.   

Mixed Storage:

Since video monitoring network is quite complex, for application requiring high storage security and reliability, deployment with both concentrated storage and front end storage can be adopted because it consists of advantages of both which can avoid potential risk.Thus, mixed storage is a better choice but it will bring complex management and high construction cost. Decision should be made according to actual situation.Adopting latest IP video product and using multi media technology, communication technology, digital video compressing, monitoring technology and computer network technology as the core, Winsion's digital video monitoring system transmits and controls the real time images of the key positions in public site  to achieve multi level remote video monitoring and seamless connection with other systems. It provides completely abundant functions. It also provides more comprehensive video data for railway transport management and railway passengers service.The advanced network video recording technology can store the data of video encoder into the computer array in real time through the network.