3VR’s License Plate Recognition (LPR) plug-in version 1.0.1.1547 and above is supported with 3VR’s Release 8.1.1.x and 7.3.2.x and above. Enhancements delivered as part of the release include the following:
3VR’s License Plate Recognition (LPR) plug-in adds unique license plate recognition and tracking capabilities to any appliance/VMS Server.
There are two versions of the LPR plug-in, standard and premium. Both versions are capable of the following features:
In addition, premium LPR offers the following features:
Standard and premium LPR are installed together in one plug-in package. Premium LPR is unlocked using a licensing key provided by 3VR. See section 4.2 for more information about premium LPR licensing. |
Prior to installing and configuring the LPR plug-in you should ensure that the location where you plan to capture license plates meets the following specifications:
Cameras should be positioned to record rear license plates. Images of front license plates are not ideal because car headlights produce image sensor blooming that can adversely affect camera gains. Additionally, front license plates are not illuminated by the car and thus cannot be read in low-light conditions.
For standard LPR, license plates should be recorded at a choke point where traffic comes to a complete stop (e.g., toll booth, vehicle gate, stop sign, etc.). Premium LPR is capable of capturing plates on cars moving up to 20 miles per hour (32 kilometers per hour).
4 3VR VisionPointTM 3VR License Plate Recognition Installation and Configuration Guide LPR is possible with both analog and IP cameras. For IP cameras, video quality must be set to “highest” (if there is no video quality setting, set to lowest compression). Use wide dynamic range cameras for outdoor lighting situations.
Uniform lighting is ideal. Backlighting (bright conditions behind the car) will negatively affect performance. Changes in lighting conditions throughout the day should be considered.
All of the license plate numbers in this document have been modified for privacy. |
For accurate license plate readings, plate characters in the field of view should appear between 30 and 45 pixels high. Estimate positioning based on the camera’s resolution using the following chart:
| Resolution | Megapixels | Approximate Max Car Widths* | Maximum Width |
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| Analog | 0.3 | 1.0 | 5' (1.5 m) |
| 1024 x 768 | 0.7 | 1.4 | 7’ (2.1 m) |
| 1280 x 1024 | 1.3 | 1.8 | 9’ (2.7 m) |
| 1600 x 1200 | 2.0 | 2.2 | 11’ (3.3 m) |
| 2048 x 1536 | 3.0 | 2.9 | 14.5’ (4.4 m) |
Choose to offset the camera either vertically or horizontally, and use the tables below to judge how far from the recording point a camera may be mounted:
| Horizontal Distance to Car (D): | 10’ (3 m) | 12’ (3.7 m) | 16’ (4.9 m) | 20’ (6.1 m) | 30’ (9.1 m) | 40’ (12.2 m) | 50’ (15.2 m) |
| Max Mounting Height (H) | 7’ (2.1 m) | 8’ (2.4 m) | 10’ (3 m) | 12’ (3.7 m) | 17’ (5.2 m) | 22’ (6.7 m) | 27’ (8.2 m) |
| Horizontal Distance to Car (D): | 10’ (3 m) | 12’ (3.7 m) | 16’ (4.9 m) | 20’ (6.1 m) |
| Max Mounting Side Deflection (M): | 5’ (1.5 m) | 6’ (1.8 m) | 8’ (2.4 m) | 10’ (3 m) |
Diagonal mounting (positioning the camera both above and to the side of the recording point) is not recommended. |
Also you may have to configure premium LPR using a monitor, mouse, and keyboard connected to the 3VR system. However, in order to license the LPR plug-in you will need to copy and paste very long text strings (30+ characters), and this functionality is not available from the local console. |
Prior to installing and configuring analytics, you must enter the system-specific license key that was provided to you at the time of purchase.
If you do not have access to the original order confirmation email, you can look up the license key by the appliance’s serial number on the 3VR Support Portal (go to http://partners.3VR.com, sign in with your Support Portal account, then click the Obtain System License Key link).
After you have obtained the license key, enter it in the License Settings dialog in System Manager:
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| 3. In the License Settings dialog, click Add/Update License Key. 4. Type the license key in the pop-up box. 5. Click the Add/Update License Key button. 6. The License Settings window will update to reflect that a license key was applied. 7. Click Close to return to the Configure panel. |
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3. In the Bind Plug-in to Cameras dialog box, click the check box beside each camera that should be configured to capture license plates. 4. Click OK to return to the Configure panel. |
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The first step in plug-in configuration is to edit the global settings. To access this dialog:
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In the Edit Global Settings dialog, open the Plate Region drop-down menu and select the appropriate value:
If a value other than US_Standard was selected for the Plate Region (step 4.1), you will need to enter a valid license key for premium LPR before proceeding with configuration:
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7. In the pop-up box that appears, click Restart to proceed. When the restart is complete, verify that the plug-in was correctly licensed: 8. Sign in to System Manager. |
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12. If more cameras are bound than are licensed or there is another problem with the Licensing Answer, the Licensing Status
13. If necessary, unbind cameras and restart the 3VR software, then re-check the Licensing Status. |
The following settings must be configured for each camera |
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In the Plate Angle tab of the Edit Settings dialog, click and drag the end points of the line so that it is represents the tilt of a typical license plate as it appears in the camera view. This setting help the LPR algorithm compensate for a camera that is positioned slightly to the left or right of the capture point.
The Plate Angle line should be a wide line that is parallel to the bottom edge of the license plate.
Plate angle with an downward tilt of approximately 2 degrees (camera is positioned slightly to the right of the car)
The slope of the plate angle can be a maximum of 15 degrees; if the plate angle is greater than 15 degrees it will reset to 0.
If the license plate at the capture point appears tilted like the image to the right, this means that the angle is too extreme to reliably capture license plates. You must re-position the camera so it is directly behind the capture point.
Cameras with a wide field of view encompassing two or more traffic streams must have lanes configured in the field of view. Lanes are configured in the Lanes tab of the Edit Settings dialog.
To draw a new lane:
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In the Parameters tab of the Edit Settings dialog, edit the License Plate Speed setting. The options are:
Configure the License Plate Speed setting based on the speed of the cars at the license plate capture point. Under 10 mph / 16 kph should be used in slow and stopped traffic zones to reduce the rate of false positives. Deployments where the car does not stop will yield better results with this value set to Under 20 mph / 32 kph. |
Saving Settings
When you are finished editing the LPR settings for the current camera, click the OK button at the bottom of the Edit Settings dialog. Repeat the steps in this section for any remaining cameras bound to the LPR plug-in.
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To verify that the LPR plug-in has been correctly configured, check for recent license plate events in 3VR OpCenter:
The remaining settings in the Edit Settings dialog should only be modified from their defaults if LPR results are unsatisfactory.
| This setting controls the amount that the text on a license plate can vary in size from the size specified by the orange Text Size box. |
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| Increasing this value will result in more false positives and also increase the CPU load required for the analytic. Decreasing it will result in fewer license plate matches (as some plates may be rejected due to their out-of-bounds height). |
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Default: 0.3 seconds
Reduce this variable if you are working in a high speed environment.
Lowering the value for this setting will also result in more false positives. |
Default: 60.0
Each LPR result has an internal confidence score associated with the LPR event. Setting this number higher will result in fewer false positives but may result in more false negatives (missed plates). A lower confidence minimum will result in more false positives but fewer missed plates.
Default: 5.0
Increasing this will result in more images around a car motion event being processed, increasing the plate accuracy and detection rate. Higher values will have increased false positive risk compared to lower values.
The following setting is only available to the engineering-level login credentials. Please contact 3VR Technical Support if you need to change this setting. |
Default: Zoomed
This setting determines how the images are displayed on a license plate event card.
Zoomed thumbnails show only the text of the license plate itself, cropping out the rest of the camera view.
Whole-scene thumbnails show the license plate in an uncropped still of the entire camera view.
Composite plates show both the cropped license plate and the uncropped frame.
Default: On
Analog cameras in well-lit conditions usually benefit from having this setting turned to Off.
If your system is capturing license plates in low-light conditions or is using IP cameras you should leave this setting turned On (default).
Default: On
In the United States, many vehicles have license plates with vanity or advertising borders surrounding the plate.
This setting controls whether the LPR plug-in takes borders into account when identifying license plates. By default, this setting will be On.
If license plates with borders are uncommon or illegal in the state of the installation location, this setting should be changed to Off.
Default: 10
In environments with lots of background noise within the field of view, setting the threshold for noise sensitivity above 10 will reduce both CPU utilization and false positives.
) to freeze the video on the current frame.
