The Application Of GB/T 28181 In Subway Vehicle-Mounted Monitoring System

As an important part of the subway system,subway video monitoring system plays a key role in subway security guarantee.With the expansion of the monitor market,a growing number of manufacturers nowadays join this field.But because of the openness of code of network protocol,companies develop their own private protocols basing on their different understanding,that makes the products produced by different manufacturers can not be very compatible.In the meantime it brings the discommodity to the connection and maintenance.In order to solve this problem,relevant departments promulgates the GB/T 28181 "Security and protection video monitoring network system technical specification for information transport,switch and control".Afterwards,for making the vehicle monitoring system meet this standard,and ensuring compatibility across the factories and systems,the development of the user agent which is based on the standard is researched.The main researching contents of this paper is as follows:1.Referred to GB/T 28181,the protocol which includes the format and structure of SIP is studied detailedly.Then the network structure of SIP domain of monitoring is analysed,so that the feasibility of the user agent can be ensured.In addition,some other technic standards which includes the coder and decoder format of media and the technic of the transmission of code stream are researched.2.Referred to the standard,the user agent is designed and developed.First of all,according to the business need,the networking of monitoring is analysed,and the levels of the functions of the user agent is divided.Then,referring to the control and transmission process and the protocol interfaces,the interaction conversation among the network entities is designed.In the end,to achieve the functions,the code has been written.By means of the thread running and message analysing by using of the oper sourse protocol stack oSIP/eXosip,the reception,analysis and sending SIP message are finished.Meanwhile the functions of the device information query,device control and media playing are achieved.By passing the test of the official test software-SPVMN video monitoring networking test software,the user agent reaches the expected goal.And the network interconnection among the devices in the vehicle monitoring system can be achieved,which showes that it meets the requirement of the standard of GB/T 28181.