Automatic Number Plate Recognition (ANPR)

ANPR is a detection tool that reads license / number  plates of vehicles in FoV.

To configure ANPR, do as follows:

1. Select the License plate recognition object.
   

2. If you require using this detection tool for real-time number plate recognition (see Configuring real-time vehicle license plate recognition), set the corresponding parameter to Yes (2).

3. If you need to enable recording of metadata, select Yes from the Record Objects tracking list (3).
4. If a camera supports multistreaming, select the stream for which detection is needed. Selecting a low-quality video stream allows reducing the load on the Server (4).

5. If necessary, enable advanced image analysis (1).

   Yes – improves the quality of recognition under adverse conditions (for example, if the characteristics / settings of the camera do not fully meet the requirements, or in bad weather).  The processing time of the frame increases by 20-30%, depending on its size.  Under normal conditions, this setting does not affect the quality of recognition
   

6. To recognize the numbers at sharp angles with respect to the camera, select Yes in the Algorithm of recognition of distorted LP image field (2).

7. Set the image contrast threshold (3). The default value is 40 . On a high-quality image, increase this value to 50-60. If the image has poor contrast, lower this value. 

8. In the appropriate fields, select one or more countries for ANPR (4).

   Important

   The more countries you select, the slower the recognition and the greater the likelihood of the recognition error.

9. Analyzed framed are scaled down to a specified resolution (1, 1920 pixels on the longer side). This is how it works:

   1. If the longer side of the source image exceeds the value specified in the Frame size change field, it is divided by two.

   2. If the resulting resolution falls below the specified value, it is used further.

   3. If the resulting resolution still exceeds the specified limit, it is divided by two, etc.

      Note

      For example, the source image resolution is 2048 * 1536, and the limit is set to 1000.

      In this case, the source resolution will be divided two times (down to 512 * 384): after the first division, the number of pixels on the longer side exceeds the limit (1024 > 1000).

   

10. Select the current license type (2).

    License	Description
    Search in archive	Basic ANPR Search License. Attention! This type of license provides a 30-sec delay between the number recognition and the corresponding event.  (see Vehicle number plate recognition and search).
    25 FPS or 6 FPS	The 25 FPS license has a priority. The 6 FPS license is used only if you have no 25 FPS license. You cannot use the number plate recognition function if you have no FPS licenses purchased.
    25 FPS	The "Fast" license allows you to process video feeds up to 25 fps with a maximum vehicle speed of 150 km/h. You have to obtain an appropriate license to make ANPR work.
    6 FPS	The "Slow" license allows you to process video feeds up to 6 fps with a maximum vehicle speed of 20 km/h. You have to obtain an appropriate license to make ANPR work.

    Important

    All license types except the standard one (Search in archive) require the hardware key or the software key activation (see Activating a software license key for the ANPR).

    You can use a 60-day trial key (see Activating the trial version of the ANPR via a software key).

    Important

    On a virtual machine, you may use only a hardware key. To use a hardware key, select the 25 FPS or 6 FPS license type.

11. To set up a number plate recognition event:

    1. Specify the minimum percentage of similarity between the recognition result and the corresponding number plate template, for positive LPR result (7). Use this parameter to filter the results by reliability.

    2. By default, a number plate recognition event is registered after a track containing a number plate disappears from FOV. You can set the moment of registration to a Timeout in seconds (9), or to reaching a similarity percentage specified in the LP display quality field (3). If both parameters are set to non-zero, the recognition event will be registered upon matching the first condition.

       Note

       The LP display quality parameter value must be no lower than the Minimum similarity value.

12. Set the maximum and minimum width of the vehicle number plate as a percentage of the FoV width (4, 6).

    Important

    The Minimum LP width parameter affects the CPU load as follows: the higher the parameter is, the higher the load.

13. Specify the maximum number of recognition threads (5). If the value is 0, the recognition process will occur in the same thread that starts it.

    Important

    The cumulative value of this parameters across all LPR detection tools must not exceed the number of CPU cores and is limited to 100.

14. Set the number of frames required for LPR / ANPR (8). This is though a necessary condition, but not sufficient for the first output. This condition delays LPR output.  This parameter allows to increase the reliability of the results, as well as to hide false positives.

15. In the Tracker Timeout field, set a time interval in seconds after which the tracking of a vehicle is reset (10).

    Note

    Use this setting to eliminate double-triggering in such cases as, for example, another recognition of the same number after it has been obstructed for some time, and then reappears in scene.

    If you set Tracker Timeout to a value greater than a probable time of obstruction, the detection tool will not double-trigger.

16. You can configure an ANPR zone in FoV. The zone is resized by moving the anchor points.
    

    Note

     For your convenience, you can click the  button and configure the mask on a still frame / snapshot. To undo, click this button again.

    Note

    Detection zone is displayed by default. You can click the  button to hide the zone. To undo, click this button again.

17. Click the Apply button.

Configuration of ANPR  is now complete.