Why time synchronization (NTP) of monitoring systems is important

Why time must be accurate

1. Evidence validity: When the video is used as evidence, the time stamp error will directly affect the credibility. It was even questioned as invalid evidence.
2. Multi-device association: Multiple camera images of the same event, if the time is inconsistent, Unable to piece together a complete timeline.
3. Comparison with other systems: access control card swiping records, alarm host records, POS transaction records Need to correspond to the video time.
4. Platform docking: When docking with platforms such as GB/T 28181, excessive time deviation will lead to abnormal registration and playback.

Common sources of time deviation

• The equipment is not calibrated when it leaves the factory and is put into use directly after installation.
• The built-in battery (RTC) is exhausted, and the time will return to zero or return to the factory value after a power outage and restart.
• If NTP is not configured, long-term operation will produce accumulated drift (ordinary crystal oscillators may deviate by tens of seconds per month).
• Incorrect time zone setting (common deviation is 8 hours, i.e. UTC is confused with UTC+8).
• Daylight saving time is not set properly.

Configuration method

1. Self-built NTP server in the intranet (recommended): Deploy an NTP server in the center, All cameras and NVRs are pointed at it. It does not rely on external networks and has the best accuracy and stability.
2. Use public NTP: such as ntp.aliyun.com, pool.ntp.org, It is necessary to ensure that the device can access the external network and the firewall allows UDP 123.
3. Use NVR as time source: Some NVRs support unified time adjustment for connected IPCs. The simplest configuration, suitable for small and medium-sized systems.
4. Set the synchronization period uniformly on the NVR/platform side (recommended to be 1 hour or less).

Implementation Points

• The time zone is set to UTC+8 (Beijing time) and daylight saving time is turned off.
• Spot check one by one after school hours, do not assume that the configuration has taken effect.
• Recalibrate the time after replacing the motherboard battery.
• Recheck the time after power outage and restart (a typical symptom of RTC battery failure).
• Check the time deviation of the entire network regularly (monthly), and troubleshoot if it exceeds 2 seconds.

Acceptance Criteria

It is recommended that the deviation of all devices from the standard time be controlled within 1 second. You can use your mobile phone to capture the network time and compare it with the time in the camera screen for quick verification.