Advanced Configuration
Intrusion Detection
This section describes how to fine tune the input video stream parameters to maximize the accuracy of the intrusion detection algorithm.
IMPORTANT: Camera settings must always match the input video stream parameters. Please update these values simultaneously.
For most of the cases we suggest to use 1280x720p stream resolution at 2 FPS. The rest of the section covers details on how to fine tune the streams for more specific cases.
Note: All these optimizations applies only for the intrusion detection alarm type!
Note: Optimal stream parameters can be different for VMS storage and for analysis. Make sure your IP cameras supports multiple streams to fully exploit the optimizations described below.
Moving cameras
The intrusion detection algorithm of U-alarm works with fixed cameras or PTZ cameras which are stationary most of the time. When the camera is moving the intrusion detection accuracy drops. The false alert rate will stay still but it is less likely it will find the real intruder if the camera is moving. This version of U-alarm is not optimal for intrusion detection on continuously moving cameras.
Person detection distance
The intrusion detection algorithm of U-alarm detect persons in wide distance range but the optimal person height range is between 30 and 300 pixels. Accuracy drops gradually below 30 pixels or above 300 pixels.
Because the algorithm always works optimally in the 30-300 pixel range the effective person detection range depends on the camera resolution. Detection range can vary from 1.4 meter to multi hundred meters. U-alarm has successfully demonstrated intrusion detection at 400 meter range using high level of optical zoom.
If the desired person detection distance is known the following table can be used to set the optimal camera resolution:
| Vertical field of view (degrees) | Frame height (pixels) | min range (m) | max range (m) |
|---|---|---|---|
| 100 | 576 | 1.4 | 13.7 |
| 100 | 600 | 1.4 | 14.3 |
| 100 | 720 | 1.7 | 17.1 |
| 100 | 1080 | 2.6 | 25.7 |
| 75 | 576 | 2.1 | 21.3 |
| 75 | 600 | 2.2 | 22.2 |
| 75 | 720 | 2.7 | 26.6 |
| 75 | 1080 | 4 | 39.9 |
| 40 | 576 | 4.5 | 44.8 |
| 40 | 600 | 4.7 | 46.7 |
| 40 | 720 | 5.6 | 56 |
| 40 | 1080 | 8.4 | 84.1 |
Note: To detect persons at very close distances (1-2 meters) the camera resolution can be surprisingly low (eg. 576p)
Note: In case of 4K cameras U-alarm range is over 50 meters!
Frame rate and maximum number of streams
U-alarm currently runs on Nvidia Jetson TX2. (Jetson NX will be supported in future versions.)
One TX2 device can run the person detection algorithms at 8 FPS. This can be shared among multiple streams, see the table below:
| # of streams | FPS per stream | comment |
|---|---|---|
| 8 | 1 | for long range cases where targeted person wont cross the scene within 1 second |
| 4 | 2 | optimal in most of the cases |
| 2 | 4 | slightly increased accuracy or for very short range where people can cross the scene fast |
| 1 | 8 | maximal accuracy or for very short range where people can cross the scene fast |
Note: Expected total FPS for the NX boxes will be between 24-30
Night vision
The person detection algorithm works well at night if the cameras has active infra emitters. U-alarm has successfully demonstrated intrusion detection at 400 meter at night using targeted infra emitter technology.
Note: Make sure your camera's active infra range is aligned with the desired distance range.
Note: Make sure your camera cover is clear. Dirt on the camera cover can heavily effect the night vision accuracy.
Video codec
Heavy compression negatively effect the accuracy of the person detection. Make sure to set the camera for the highest possible quality within your network bandwidth constraints.
Note: Consider using lower FPS and resolution based on the tables above to achieve higher image quality using the same bandwidth.