What is ANR re-recording after network disconnection? How to ensure complete video recording in weak network scenarios

Problem background

In the conventional architecture, the camera is only responsible for collection and encoding, and the video is stored centrally in the back-end NVR. Once the network is interrupted, The recordings during this period will becompletely lost. The risk is particularly high in the following scenarios:

• The point where the wireless bridge returns the signal (affected by weather and obstruction).
• Long-distance links across factories and buildings.
• Branch offices with unstable networks or shared bandwidth.
• Key points with weak links.

The principle of ANR

The workflow of ANR (Automatic Network Replenishment):

1. Under normal conditions: the camera pushes the stream to the NVR, and the NVR records centrally (the camera does not record or only records a small amount).
2. When the network is interrupted: the camera automatically writes the video to the local SD card without interruption.
3. After the network is restored: NVR detects the interruption interval and actively pulls the missing recordings from the camera SD card . Complete it into your own storage.
4. After completion: Users can seamlessly play back the complete timeline on the NVR without having to read the SD card separately.

Deployment Points

• The camera must support ANR and insert an SD card (surveillance-grade high-endurance card recommended).
• NVR needs to enable the network disconnection re-recording function, and some brands require the front and rear ends to be of the same brand.
• The SD card must have enough capacity to cover the expected outage duration: At 4Mbps bit rate, 64GB can be stored for about 30 hours, and 128GB can be stored for about 60 hours.
• Supplementary recording will occupy network bandwidth. It is recommended to arrange supplementary recording during low business peak or speed limit.
• Do not power off or restart the device during the make-up recording period.

SD card selection and maintenance

• Use High Endurance (High Endurance) dedicated monitoring card. Ordinary cards will become damaged after a few months of continuous writing.
• Watch the TBW (total writes) metric.
• Check the health status of the card regularly (such as every six months) and replace it preventively if necessary.
• Don't rely on the SD card as your only storage, it's just a fallback.

Supplementary measures

• Dual links (wired + wireless backup) can be used at key points.
• Configure link detection and alarms on network devices to shorten fault detection time.
• Regularly check the integrity of the recordings and discover long-term link problems in a timely manner.