Fine-tuning the VT number plate detection tool

To fine tune this detection tool, do as follows:

1. 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

   
2. 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).
3. 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. 

4. If you expect different sizes of number plates within FOV, activate the LP advanced search algorithm (4). This parameter accounts for max and min width of number plates, and, in some cases, may help increasing recognition quality and optimizing CPU load.

5. 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 (8), or to reaching a similarity percentage specified in the LP display quality field (5). 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.

6. Specify the maximum number of recognition threads (6). 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.

7. 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.

8. Click the Apply button.