Guide · Nx Witness
Reading French license plates in Nx Witness.
The IA-N Analyse plugin reads French license plates (current and former format) in Nx Witness, as an option, camera by camera. You tick “Read license plates on this camera”, draw a tight plate zone where the plate passes large and sharp, and the camera must have its primary stream analysed (at least 1280 pixels wide). Each plate read becomes an Nx event “IA-N: License plate read” and is added to the vehicle in the “Objects” tab. Reading is meant for vehicles at walking pace: access point, barrier, car park; not roads or motorways.
Updated on 21 October 2026
The conditions
What makes a good read.
- A camera dedicated to plates, framed on the passage, head-on (in front of the barrier).
- A short exposure time set in the camera: motion blur is not corrected by the software.
- The primary stream analysed, at least 1280 pixels wide: the secondary stream does not allow reading.
- Vehicles at walking pace: access point, barrier, gate, car park.
- The Plates option in the licence for this camera (the free trial includes it on 1 camera).
Step by step
Enabling reading on a camera.
- 01 / Enable
Reading
Camera Settings › Integrations › “IA-N Analyse” › “License plate reading”: tick “Read license plates on this camera”.
- 02 / Draw
The plate zone
“Plate zone (plates are only read inside it)”: a tight polygon, where the plate passes large and sharp, not over the whole lane.
- 03 / Choose
The primary stream
In the Nx camera settings, have the primary stream analysed by the integration; keep the secondary stream for the other cameras.
- 04 / Link
To an action in Nx
Nx event rule on “IA-N: License plate read”: bookmark to find the passage, notification if needed.
Passage settings
More frames while a vehicle passes.
When a moving vehicle arrives in the plate zone, the camera is analysed faster for the duration of the passage, then returns to its normal rate.
| Frames/s while a vehicle passes | 15 by default (10 to 25); raise toward 25 if plates are missed at a car park entrance. |
| Hold after the vehicle leaves (s) | 1 by default (0 to 5). |
| CPU ceiling for plate acceleration (%) | 80 by default (50 to 95), in the integration settings: above it, the passage is analysed at the normal rate. |
| Processing | The text of the plates is read on the CPU, even with a graphics card. |
Fixed rules
How a plate is kept.
- Reading only inside the plate zone, and only when a vehicle moves in it: parked cars are never read.
- Several frames vote before giving a plate.
- Zone too large: Nx reports it, because each read costs more computing without reading better.
GDPR
A license plate is personal data.
Read plates only where it is necessary: few cameras, a zone limited to the vehicle passage. Keep a short retention period in Nx (30 days at most, unless there is a justified reason) and inform people with a sign. The plugin log only keeps masked plates (AB***CD), and ordinary plate reads are never sent to the alarm monitoring centre. See the guide GDPR and video analytics in Nx Witness.
Frequently asked questions
French plates in Nx Witness
Another question? Our sales team will answer.
Which plates does the IA-N Analyse plugin read?
French license plates, in the current format and the former format.
Can plates be read on a road or a motorway?
No. Reading is meant for vehicles at walking pace: access point, barrier, gate, car park. Roads, expressways and motorways are outside its scope.
Do you need a graphics card to read plates?
No. Plate reading is always done on the CPU, with or without a graphics card.
Why is no plate read?
Common causes: secondary stream analysed instead of the primary stream, plate zone badly placed, blurred plate (exposure time too long), or all the licence's Plates places already taken. Nx then shows a message in the camera settings.
Where do I find the plates read in Nx?
Each read gives the event “IA-N: License plate read”, and the plate is added to the vehicle in the Nx “Objects” tab.
Also worth reading
To find out more.
Nx Witness is a trademark of Network Optix, Inc.; DW Spectrum, of Digital Watchdog.
A car park entrance or a barrier to equip?
The 30-day free trial includes license plate reading on one camera.