Recognition settings tab

When you are setting up XProtect LPR, the system auto-configures the recognition settings using your snapshots. You can change the settings but be aware that manual adjustments can significantly impact the recognition performance.

Action buttons

Change, update, and validate auto-configured settings.

Name	Description
Validate configuration	Test that license plates are recognized as expected.
Auto-configure	Discard manual changes and auto-configure settings.
Snapshots	Add or delete snapshots.

Recognition area

The recognition area defines which part of the image the system uses to detect license plates. How you set it up depends on your use case.

Detecting license plates only: If your goal is strictly license plate recognition, define a smaller, clearly framed area that includes only where the plate is visible—ideally throughout the vehicle's movement in and out of the image.
Milestone recommends selecting a clearly defined, well-positioned recognition area for the best results and to avoid false recognitions. Setting up a larger recognition area allows the system to analyze the entire vehicle body, which improves detection of visual features.
Detecting vehicle properties: If you want to detect vehicle properties in addition to detecting the license plate, such as make, model, or color, adjust the recognition area to cover the entire part of the image where the vehicle will appear.

The red area shown in the image below shows the areas of the camera image that are excluded from the recognition area.

Image showing the red areas that are not included in the LPR camera's recognition area.

When defining the recognition area, you can click:

Clear to remove all selections and define a new area.
Undo to revert to your last saved selection.

After changing your LPR camera settings, click Validate configuration to check if license plates are recognized as expected.

Character height

Set the minimum and maximum character height (in percent) to match the real height of the license plate characters as closely as possible.

These character settings affect the recognition time and process. The smaller the difference between the minimum and the maximum character height:

The smoother the LPR process.
The lower the CPU load.
The sooner you get the results.

The Character height settings in the Properties window for LPR cameras.

The overlay in the snapshot shows the current character height setting.

To compare it with the real license plate, drag the overlay over the license plate in the image. The overlay resizes when you adjust the character height settings on the right. Use your mouse wheel to zoom in for a closer view.

Name	Description
Minimum height	Set the minimum character height for including license plates in the recognition process. If the real license plate characters are smaller than the value you specify, the system will not start the recognition process.
Maximum height	Set the maximum character height for including license plates in the recognition process. If the real license plate characters are bigger than the value you specify, the system will not start the recognition process.

After changing the settings for your LPR camera, validate your configuration to check if the system recognizes license plates as well as expected.

Advanced settings

A license plate recognition process has two steps: detecting the license plate and reading the characters on it. Click Advanced settings to configure the parameters between processing speed and recognition quality.

High recognition quality	Processing speed
More accurate plate and character recognition.	Returns recognition results faster.
Requires more computational power.	Uses less computational power.
Increases CPU load.	Reduces CPU load.
Takes longer to return results.	May lower recognition accuracy.

The Advanced settings in the Properties window for LPR cameras.

When the optimal results are met, the recognition process stops and returns the license plate it recognized at that point.

Name	Description
Compensate for interlacing	If your LPR camera records interlaced video, and you see a combing effect in the de-interlaced image in LPR, select this check box. This might improve the image quality and recognition results.
Maximum number of frames processed per second	Limit the number of frames your system processes every second. If you keep this setting low, you can increase the frame rate on your camera without adding unnecessary load to your LPR server. Unrestricted: Remove the top limit. You will risk increasing the processing time and the CPU load.
Maximum number of seconds used per frame	Limit the number of seconds your LPR can spend on recognizing one frame. If adjusted, the recommended value is 0.2 seconds per frame. Unlimited: Remove the top limit. You will risk increasing the processing time and the CPU load.
Discard recognitions below	Discard recognitions with a confidence level below the value you specify. Increase this value to get fewer but possibly more accurate recognitions. Decrease this value to get more but potentially less accurate recognitions.
Maximum number of license plates recognized per frame	Recognize several license plates simultaneously. For example, relevant for cameras recording multi-lane roads, where many license plates must be recognized at the same time. Unrestricted: Remove the top limit. You will risk increasing the processing time and the CPU load.
Time span in seconds for avoiding partial recognitions	Delay all recognitions for the time period you specify. This is to avoid that the same license plate is recognized several times as different license plates. The system will wait for a better recognition and only accept the most complete recognition. Before changing this setting, ensure no irrelevant moving objects block the view of your LPR camera.

After changing the settings for your LPR camera, validate your configuration to check if the system recognizes license plates as well as expected.