- IPC 2014-04-02 11:55:20
Construction and installation of network cameras Conditions
Network Camera (IPCamera), as the name suggests , is the camera + network , and its main point is that video and network technology . The flow of data from the network camera to see is : lens-> sensor-> isp-> encoding chips - > Network , to build a network camera , video capture from the front to the stream transmission , a lot of factors to consider , including image quality , video capture, codec chip selection criteria to follow , network transmission and network security . From the point of view of constructing multiple network cameras were discussed.
With push technology development and user demand, high-definition video gradually evolved from the early SD, and HD camcorder is the most critical component front-end acquisition and encoding chips . In banking, business offices and other monitoring applications , often in front of the camera lens at the gate , while the interior is light, outdoor sunlight , indoor light levels vary greatly hair ; road monitoring and surveillance in public places , most of the outdoor areas daytime affected by sunlight , affected by various lights at night , foreground and background light contrasts ; entertainment control, almost all indoor places , light to light -based, instability, overtly or covertly , often will cause a lot of light and dark contrast. To under different lighting conditions , to achieve a satisfactory image , you need a support for low-light , wide dynamic camera , Sensor and ISP selection is critical. Sensor, ISP, with the three encoding chips , directly affecting the image quality . Current mainstream HD Sensor (720P/1080P) basically do not bring ISP, require additional distribution . Thus from the whole structure , cost, power consumption , image quality and other considerations , choose a chip embedded ISP code would be a good solution .
Coding and Bandwidth
Within the limited bandwidth , how to transfer high-quality video data network camera focus. Phone monitoring due regardless of location convenience, a growing number of applications, such as baby online shops monitoring. Low bandwidth wireless networks to meet the needs of mobile phone monitoring would require ultra-low bandwidth ( eg 64kbps), but also to achieve high-quality video compression . Currently the main use of video encoding formats are JPEG / M-JPEG, MPEG4, H.264.
· JPEG / M-JPEG compressed image quality is good, but the large amount of data , large bandwidth ;
· MPEG4 compression ratio, less data , most mobile terminals support MPEG4 decoding, early wireless monitoring ( phone monitoring ) using MPEG4 more ;
· H.264 in the same quality, the higher the compression ratio relative to MPEG4 , the data amount is smaller , but the coding / decoding chip consumes a higher performance . With the development of mobile phone technology, the vast majority of mobile terminals has been able to smoothly support H.264 decoding.
These types of advantages and disadvantages , H.264 because of good image quality, compression rate, less data for network transmission , and many other excellent features, network camera are increasingly becoming the preferred video compression format .
One of the high-definition network camera is the bandwidth constraints of development , focusing on both the professional market or the domestic market , the bandwidth network cameras are concerned , the same quality, reduce the use of bandwidth will make network construction costs. As the telecommunications access network upgrade , the current ADSL downstream bandwidth is the theoretical value of many families 4Mbps, but actually only reach 3Mbps, 720P resolution video . If the compression rate can be controlled in the following 2Mbps , the network bandwidth will not become a bottleneck , while reducing storage costs.
Webcams in practical applications , mainly audio and video data are stored remotely, such as IPSAN / NAS, it can not only provide remote live features , while also supporting cell phone on demand . These types of streams , require different storage requirements of clarity and stream fluency ; live stream and the network bandwidth of factors need to be considered ; Mobile VOD streams require very low bandwidth (64kbps), but also to achieve high-quality images . This same video input source need to output multiple streams : 720P +, D1 +, QVGA, not the same resolution and bit rate . Some scenarios also need to output JPEG / MJPEG. In short, only the strong coding performance , support for multi- stream IPCamera in order to better meet the needs of a variety of scenarios. In order to meet multiple clients simultaneously access , or that there are multiple streams recipients , IPCamera network processing capabilities must be further improved , considering the selection of high- frequency , Gigabit Ethernet port , the main chip to increase network throughput IPCamera capacity.
As a network device, you must follow certain protocol standards , in order to achieve interoperability with NVR, CMS and other equipment . If fragmented, difficult to install network devices will actually works . However, in engineering applications, and can not guarantee that all devices from the same vendor , you need to meet certain standards, in order to achieve interoperability . Currently associated with the global standard domestic eyes, wide horizon and other international has ONVIF, PSIA. Their common goal is to promote the perfect network monitoring equipment interoperability . ONVIF and PSIA are using HTTP, XML and other Web technologies , but also in the media streaming is also consistent use RTPoverUDP, RTPoverRTSPoverTCP, HTTP protocol. On the control data , ONVIF use SOAP framework , PSIA REST framework is adopted . PSIA control mode with the current HTTPCGI more commonly used methods similar manufacturers . Careful analysis of two specifications , although the discrepancy, but similar, the device can be done mostly supports both PSIA and meet ONVIF, in fact , many manufacturers are both members of PSIA , ONVIF is also a member .
As a network camera network products , necessarily involves a series of complicated configuration IP, routing , etc., for the average user, its installation there is a big difficulty. In the home market , the typical scenario is IPCamera applications connect to the router , the router and then connect ADSLModem Internet dial-up access . To reduce installation difficulty of users, so that users can quickly use , refer to the following suggestions .
· IP address auto-configuration , such as the use of DHCP, and is enabled by default ; support Auto-IP (UPnP), ZeroConf; while small NVR surveillance environment , if you use a switch interconnect , no router or DHCP server provides automatic IP configuration (Auto-IP , ZeroConf) is particularly suitable ;
· Use the network with multicast and broadcast network to complete discovery , such as UPnP (PSIA), Bonjour (PSIA), WSDiscovery (ONVIF);
· Automatic router port configuration . IPCamera External use only one port , control data and media data using a Web interface . Such as controlling the use of CGI mode , media transmission using RTSPoverHTTP, control and data will follow the HTTP protocol , which will bring an additional benefit - can go through the PC 's firewall. Currently, almost all routers support upnp function , IPCamera can use the UPnP protocol to initiate a request to the router , the router automatically configure port forwarding , so as to avoid the user to manually configure the router login .
Under NVS environment , automatic IP allocation, device discovery technology basically allows IPCamera " free installation " be used to achieve the effect of plug and play close to the user experience with analog cameras and DVR use . Families need access to the Internet environment , using the UPnP protocol , and with DDNS service, you can minimize the time involved in the installation of the user. At present, many manufacturers offer PC terminal device search tools to complete discovery , IP configuration, access IPCamera other functions, it is also a good way to reduce the difficulty of the user to install .
Currently, the hacker software to users flooding caused a great threat to information security . Network camera need all-day work , and the transmission of audio and video data related to privacy, security is of particular concern . Application layer security measures can be IP / MAC black and white lists , user rights management , firewalls, etc. ; transport layer encryption transmission can be taken for the control of information , or the information is encrypted stream , such as AES, DES, 3DES , etc. Less information than the data control , data encryption, relatively fewer resources consumed , but if it is calculated using the software , the burden is still heavy on the main chip , if the main chip can provide encryption coprocessor module , it will greatly reduce the main chip performance consumption, remaining more resources to deal with other applications.
Saving and environmental protection , the relationship between human survival and development, has become a worldwide topic , security monitoring in the global security escort , nor give the earth to bring the burden of too many resources consumption. However, from a security point of view the use of the network camera , standby , hibernate is not realistic. Therefore, choosing sensor, isp, the main chip and other components , to fully consider its energy consumption and emissions , and make sure the energy saving .
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