The Research And Design Of A New Generation NVR Device

Nowadays, security is becoming more and more important in society, and the video surveillance is the important part in security domain. With the changing of the people's requirements, and the development and application of new technologies, there are more and more video surveillance products developed, the applications of the products are becoming increasingly wide, new concepts and products are continuously being brought out and developed. This article will introduce a NVR product's researching and designing.The new generation Network Video Recorder device (NVR) is a network based video surveillance device, and is a device that controls and manages the IP Cameras and IP Encoders (Latter, IP Camera will be a general term of all IP A/V devices that as an input source of NVR, containing IP Camera and IP Encoder).In this article, first, we did requirements analysis of NVR. The requirements were divided into three parts. The first part was about the introduction and analysis of basic functions. These basic functions contained: the access of IP Cameras; live service of audio and video; recording, searching and playback of audio and video data; supporting alert handling, alert log recording and querying; supporting PTZ controlling, and so on. The second part was about the introduction and analysis of extended functions except the basic functions. For example, besides the MJPEG and MPEG4 video codec, the newest and more advanced h264 video codec was added into this NVR; the high resolution cameras were supported in this NVR; and so on. The third part was about the non-functional requirements analysis, mostly focusing on performance representation, the facilitation and expansibility of manipulation.Next, based on the features of requirements, and with analyzing the design limitation of current NVR (old NVR, the first generation), we discussed, analyzed and selected the key techniques the NVR device used, which contained the newest and mature techniques, new design ideas brought forward. Here we selected Linux as the base operating system, designed it as an embedded system; selected GStreamer to handler audio, video and alert data; selected PostgreSQL as the database system; selected RTSP as the media service protocol; and brought forward a new design idea: Device Handler, to handle different modules cameras.Next, based on the techniques selected and the new ideas designed, we made out a totally new scheme of NVR. The scheme was convenient to expand, easy to use, highly stable and strong in performance. With completing the basic functions, it also solved the known limitations, took the latter's expandability and adding new functions into account. According to the design of the scheme, the division and definition of base modules were done. On this base, it defined the application interface (VEAPI) for outsider to the NVR and the message mechanism for internal modules to interact with each other; it also defined and analyzed the basic functions and interfaces the Device Handler should implement, and the implementation requirements for these functions and interfaces; in addition, it analyzed and designed the main functions and the interactions of database system, each function modules.At the last, it was the implementation and test of NVR. The implementation of NVR was based on the divided modules. We selected Device Handler, a representative module, to do analysis of its implementation process. In the implementation process, it could also improve and perfect the design of NVR. The test of NVR was based on the analysis of requirements. The first step was to design the test cases. The test cases covered all the requirements, containing functional and non-functional respects. Then it was to do test and to analyze test results.Currently, this NVR has been basically finished, and has been trial-used by customers. There has been a good impression from the customers.