NTP time synchronization device (NTP server) accurate time synchronization scheme for network cameras

NTP time synchronization device (NTP server) precise time synchronization scheme for network cameras
NTP time synchronization device (NTP server) precise time synchronization scheme for network cameras
Compared with analog cameras, network cameras have added digital compression controllers and based on The operating system and internal clock system of the WEB management interface (which can run by itself or obtain external time as a reference) make the captured video processed and sent to the end user for display or storage through a wired or wireless network. The network camera needs the Beidou time server to provide the standard time, and the user can use the standard client software on the PC terminal or mobile terminal to monitor the situation of the target site in real time, and can edit and store the image and video data in real time , At the same time, it can also control the pan/tilt and lens of the camera for all-round monitoring.

A video surveillance system generally consists of five parts: network cameras, transmission equipment, back-end storage, network hard disk recorders, and display equipment. The most closely related to time are network cameras and network hard disk recorders.

1. Network camera problem: Some network cameras do not have a network hard disk recorder, such as a home network camera, or the device is in a closed Internet, and the time cannot be synchronized with the network, and the default time of the system is used to continue to go.

2. Problems with the network hard disk video recorder: In addition to the failure to synchronize with the standard Beijing time due to line failures, there may also be a fault with the main board of the network hard disk video recorder. Assuming that the time displayed by the monitoring system deviates from the standard Beijing time, The display time of each network camera is also different, some show a difference of about a few minutes, some show a difference of a few seconds, and the difference between the monitoring system display time and the standard time is about a few seconds, the reason for the error is each network camera and hard disk video recorder They are all individual individuals. When each walks on its own without timing, the longer the time, the greater the deviation will be. The most commonly used solutions are mainly the following two:

1. For the camera or NVR connected to the Internet, the time can be adjusted and aligned through the NTP protocol. On the network camera or DVR configuration interface, you can calibrate the clock by filling in the address of the network clock server and connecting to the Internet. Due to the complex network situation between the video surveillance network and the NTP time server in the Internet network, setting the NTP time server can complete the time synchronization of the video surveillance network, which has high reliability but poor accuracy. Due to time delay, network congestion and Factors such as the geographical location of the external authoritative clock source may also cause inaccurate clock calibration of devices in the security video surveillance network, and it is not safe at the same time. Hackers can steal video information through the Internet.

2. If it is a local area network application or a private network camera and network video recorder, you must first set up and configure an NTP clock server inside the network, and then fill in the IP address of the time synchronization server in the configuration of each network camera or network hard disk video recorder In the interface, the time synchronization can be guaranteed. Note: In this case, it is necessary to ensure the clock accuracy of the local clock server. Generally, the use of a high-precision local clock source requires a higher cost. The time synchronization device uses GPS positioning and calibration, etc., and uniformly uses a standard protocol that supports time calibration. The NTP protocol connects the device, ensures that the platform and each device comply with the clock synchronization agreement in the standard protocol, and ensures the time synchronization of the video surveillance network under the condition of low cost, reducing the problem of system clock confusion.

In fault 2, the display time of each network camera is different, the largest difference is about ten seconds, and the main problem comes from the network switching delay. It takes time to collect and encode the video of the network camera. At the same time, when the digital signal encoded by the network camera is transmitted through the network, according to the bandwidth capacity and performance of the network equipment, a certain network delay will be generated. After a digital signal, it also takes time to decode it. The network camera is located in different locations on the network. Due to the influence of many factors, the delay of each device may be different, mainly depending on the indicators, performance, quality and network architecture of network devices such as switches. If there is a decoder at the back end, it may There will be a decoding delay, and if the performance of the preview device is poor, there will be a preview delay, etc. The data transmission delay of each network camera and network video recorder in the network will definitely be delayed, and it is different. Hikvision’s latest network camera can achieve 120ms, but it is indeed a long time to achieve no delay. There is a long way to go, generally around 0.5S is acceptable.

Fault 3: The time displayed by the video surveillance system differs from the standard time by more than ten hours, and the display time of each camera is different. Some have a difference of about ten seconds, and some have a difference of more than ten hours. This problem is more complicated, and the main analysis may be Two reasons: 1. Different time zones are used: various types of cameras are used in the network, network cameras or network hard disk video recorders may use different time zones, and some use Greenwich Mean Time (GMT) , some use UTC, and some may use summer time saving time DST. When calling different time formats in different devices, they cannot be accurately identified or converted, which causes some network devices to differ. More than ten hours, you can set the time in the same time zone in advance in the configuration interface of different cameras or DVRs.

Compatibility of network cameras: Since various network cameras are used in the same surveillance network, for example, the original video surveillance network uses Huawei cameras, and the newly added cameras in the upgrade use Dahua, these different brands Some network camera video surveillance network devices are based on Linux, some are based on AIX, Solaris, and some are even based on Windows platform. There are certain compatibility issues between these different brands of network cameras and different platforms, or the time zone time of these terminals The format is inconsistent, so a large time error occurs.

Time Synchronizer Function

1. Establish time reference with GPS Beidou and other timing signals;

2. Provide 8-way NTP network timing interface, which can set any time zone;

3. The front panel displays the year, month, day, hour, minute, second, number of satellites and working status;

4. Support windows, LINUX, UNIX, SUN SOLARIS, IBM AIX and other operating system time synchronization;

5. Support the mainstream NTP/SNTP protocol in the market;

6. Support DHCP function, all network devices connected to the LAN port can automatically obtain IP addresses;

7. Excellent security performance, providing firewall protection, greatly improving the security of the internal network and reducing risks;

8. Support heartbeat detection function, multiple time servers or multiple network ports can be set to the same IP, mutual redundant backup;

9. Support WEB, SSH encrypted communication and parameter management mode of software monitoring settings;

10. Support WEB firmware upgrade, provide parameter backup and import, system local log and remote log sending and other functions;

11. Provide software and hardware watchdog design, QoS function (traffic monitoring) and network diagnosis, etc.;

12. Parameter setting files can be exported and imported;

13. The network configuration page supports internationalization (multi-language), including Chinese, English, Japanese, Spanish, French, Italian, Russian, Ukrainian, etc. User name, password and host name can be set;

14. Real-time monitoring of load, running time, real-time traffic and memory status;

15. Display real-time links, including client access time server IP, communication protocol and interactive data volume, and display historical data in the form of graphs.