Recognition settings tab

Change recognition settings manually. Based on the snapshots you provided, the system auto-configured the recognition settings. Changing these settings can greatly affect the recognition success rate.

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

To ensure best performance and avoid false recognitions, Milestone recommends that you select a clearly defined and "well-trimmed" recognition area. The area should cover only the part of the image where the license plate is visible and remains visible as the vehicle moves in and out of the image. Avoid irrelevant moving objects (people, trees, traffic) in the recognition area.

License plates are not recognized in the red area.

mc_lpr_recognition_area

When specifying a recognition area, you can click:

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

Character height

Define the minimum and maximum height of the license plate characters (in percent). Select character heights as close as possible to the height of the characters in the real license plate.

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

mc_lpr_character_height

The overlay in the snapshot displays the currently defined character height setting. The overlay grows and shrinks proportionally to the character height settings to the right. For easy comparison, drag the overlay on top of the real license plate in the snapshot. Zoom with your mouse wheel for a closer look.

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

The recognition process has two steps: 1) finding the plate(s) and 2) recognizing the characters in the plates. Click Advanced settings to define a trade-off between processing speed and recognition quality.

High recognition quality:

mc_lpr_advanced_settings

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 may improve 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.

Unlimited: 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.

Stop recognition above

Stop recognition when a license plate is recognized with a confidence level equal to or above the value you specify.

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.

The smaller the difference between Stop recognition above and Discard recognitions below values, the lower the processing time and the CPU load.

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.

Unlimited: 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.

Note: 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.

© 2019 Milestone Systems A/S