Design And Implementation Of Multi-channel Media Transmission Component

With the popularity of IP video surveillance,network video surveillance equipment is also more and more widely used.The existing monitoring network has the characteristic of regionalization and closeness,which makes the interconnection of the various hardware devices manufacturers obstructed.Under such a situation,different organizations at home and abroad are aware of the significance of the standardization of network video surveillance.They developed various standards,such as the power industry,railway industry and operator industry.There are GB28181 standard issued by the Ministry of Public Security of China,and PSIA and ONIVF agreements of foreign trade organizations.In the market background,this paper mainly designs and implements a media relay component supporting China Unicom Integrated Video Surveillance System Equipment and Client Technical Specification and ONVIF Interface Specification,which combined with the actual project of the manufacturers.Components using C ++ language are based on the linux platform.According to the modular design,the Component designs five functional modules including access device management,landing and heartbeat detection,signaling services,media session management,RTP data reception.The object-oriented design method is used in each function module to make the whole system scalabilities,which against equipment management,login and signaling abstracting out puElemrnt,login and service Group.In the realization of support for Netcom and ONVIF protocol device management at the same time,it also can expand the new protocol device.In the Netcom protocol and ONVIF protocol,the paper further studies the media session management protocol: SIP and RTSP protocol,designing the session management module to support the two protocols.The bottom of the module is implemented using the reactor model,which drives the entire SIP and RTSP protocol handshake process.In the link of the closure of the session,the paper designs the process of delayed deletion to guarantee the safe destruction in the concurrency context of the data processing tasks and session closure tasks.In the aspect of media data transmission,the paper analyzes the data format of RTP specification.By using semi-synchronous / semi-asynchronous IO multiplexing framework,the multi-channel concurrency capability in high frequency data service scenario is realized.On the other hand,by dynamically adjusting the socket low water mark to achieve the dynamic buffer,reducing the large flow of business CPU consumption at the same time,but also to ensure that the real-time streaming media requirements.Theoretical analysis and actual test results show that,in the high-traffic business scenarios,multi-channel concurrent reception completed by multi-channel broadcast component,compared to open source software Live555,the system CPU consumption fell by 60%,which provides important support for the competitiveness of NVR products.