Configuring License Plate Recognition in the ACC Software
For detailed information about configuring LPR in the ACC software, see the Avigilon Control Center Client User Guide. Please refer to the following sections:
- License Plate Recognition
- Monitoring License Plates
- Initiating a Search
To analyze license plates, the LPR engine requires a defined Region of Interest (ROI) and Image Analysis Rate to be set. Use the tables below to determine recommended image analysis rate for a defined Region of Interest of 400k pixels or 1MP. For optimal performance of the LPR engine it is generally preferable to increase the Image Analysis Rate than increase the Region of Interest.
The camera's main area of focus should be within the LPR defined Region of Interest. Adjust the camera’s focus in the Image and Display area. Auto-focus will improve the visibility of the entire scene, not just the primary plate detection area. Focusing the LPR region of interest will improve license plate detection.
The following recommendations are applicable when the camera is mounted at the recommended height and horizontal distance (20° to target) as outlined in Table 1: Camera Installation Guidelines.
Table 2: Frame Rate Recommendation (20° to target)
| Speed | Recommended Image Analysis Rate (Region of Interest = 400k pixels) | Recommended Image Analysis Rate (Region of Interest = 1MP) |
|---|---|---|
| 0 – 16 km/h (0 – 10 mph) |
7 | 4 |
| 16 – 32 km/h (10 – 20 mph) |
13 | 6 |
| 32 – 48 km/h (20 – 30 mph) |
20 | 9 |
| 48 – 64 km/h (30 – 40 mph) |
25 | 12 |
| 64 – 80 km/h (40 – 50 mph) |
30 | 14 |
| *80 – 100 km/h (50 – 62 mph) |
Not Recommended | 16 |
The following recommendations are applicable when the camera is mounted at the maximum height and horizontal distance (30° to target) as outlined in Table 1: Camera Installation Guidelines.
Table 3: Frame Rate Recommendation (30° to target)
| Speed | Recommended Image Analysis Rate (Region of Interest = 400k pixels) | Recommended Image Analysis Rate (Region of Interest = 1MP) |
|---|---|---|
| 0 – 16 km/h (0 – 10 mph) |
9 | 4 |
| 16 – 32 km/h (10 – 20 mph) |
16 | 7 |
| 32 – 48 km/h (20 – 30 mph) |
24 | 10 |
| 48 – 64 km/h (30 – 40 mph) |
30 | 14 |
| 64 – 80 km/h (40 – 50 mph) |
Not Recommended | 16 |
| *80 – 100 km/h (50 – 62 mph) |
Not Recommended | 20 |
- Use Table 3 to determine image analysis rate for all roadside mounting applications while ensuring a maximum camera to target angle of 20°.
- When drawing the ROI, cover the full lane width and include more area in the direction of travel for the vehicles.
- * For speeds above 80 km/h (50 mph):
- Increase gain to 12 dB.
- Decrease exposure to 1/2000 s (0.5 ms).