License Plate Recognition Version Details

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:

License Plate events are now stored at better resolution and quality
Search results improved with enhanced events and tagging added
The license plate background is now clearly visible even under poor light conditions
Improved similarity searches for License plate strings
Ability to distinguish text images within license plates

About 3VR's License Plate Recognition Plug-in

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:

Capture license plate data with standard resolution, commercially available cameras
Record plates at choke points (natural stopping points in the flow of traffic)
Index and search for video containing license plates
Search on partial or total license plates
Create and monitor watch lists of wanted license plates

In addition, premium LPR offers the following features:

Record license plates from traffic moving up to 25 miles per hour
Capture license plates from regions outside of the United States

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.

Environmental Specifications

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:

Application

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).

Cameras

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.

Lighting

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.

Field of View

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
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)

Mounting

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:

Vertical — Position the camera directly above the lane of traffic. The formula for calculating max mounting height (H) based on distance to the car (D) is (D/2) + 2 = H. This assumes a plate height of 2’

Sample Vertical Mounting Values


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 — Mount the camera at the same height as the license plates. The formula for calculating max mounting side deflection (M) based on distance to the car (D) is D/2 = M

Sample Horizontal Mounting Values


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.

Pre-Installation Checklist

Ensure that you have purchased LPR for the correct number of cameras for the installation. LPR SKU is as shown below.
- A4-LPR-001 - License Plate Recognition - 1 Channel Analytics Pack
Ensure that you have at least 24 hours to complete the installation. Step 4.2 of the plug-in configuration (page 8) entails sending a system-specific licensing question to 3VR Technical Support in order to obtain the matching licensing key. It can take up to 1 full business day to receive the licensing key.
Plan to connect to the 3VR appliance/VMS Server with one of the following methods:
- Laptop connected to the system using a D-Link USB network adapter or a network cable
- Connection from a remote PC over the LAN

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.

Enter System License Key

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:


In the Configure panel of System Manager, select the appliance name. The system settings will appear to the right. Click Common Operations, then click License Settings.
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.

Install LPR Plug-In

Installing LPR Plug-in Package

Launch 3VR System Manager.
In the Configure panel, click the plus sign beside the appliance name.
Right-click the Plug-ins folder and select Add Plug-in.
In the resulting Confirm dialog box, click Install to proceed.
Navigate to the folder containing the plug-in file (Plugin-LPR-1.0.1.1547-en-us.3pg ) and click to highlight the file.
Click OK. The plug-in will now begin installing.
When the plug-in is installed, it will appear below Plug-ins in System Manager.

Binding Cameras to Plug-in

Click the plug-in name to view its settings.
On the right side of System Manager, select the Bound Cameras field and click the ... button.

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.

Configuring Global Plug-In Settings

The first step in plug-in configuration is to edit the global settings. To access this dialog:


In the Configure panel, select the plug-in name to view its settings. Click Edit Settings.

Select Plate Region

In the Edit Global Settings dialog, open the Plate Region drop-down menu and select the appropriate value:

For standard LPR, select US_Standard
For premium LPR capturing U.S. plates, select US_Premium
For premium LPR capturing plates from another region, select the region.

License Plug-in (Premium LPR Only)

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:

Copy (select the text and press Ctrl+C) the 32-character code from the Licensing Question field in the Edit Global Settings dialog.
Paste (press Ctrl+V) the licensing question into an email to 3VR Technical Support (support@3VR.com).

In your email, you must include the system serial number and the number of cameras of PLPR purchased (reference the PO
number of the order if available). Please also provide your contact information and the customer/reseller company name.
3VR Technical Support will respond with the matching 30-character key within 1 business day.
Copy (CTRL-C) and paste (CTRL-V) the key from the email into the Licensing Answer field in System Manager.
Click OK to save and return to the Configure panel.

The Licensing Status field will display “Invalid” until the 3VR system software is restarted.
In the Configure panel, right-click the appliance name and
select Restart 3VR Software.

7. In the pop-up box that appears, click Restart to proceed.
Wait 1-2 minutes for the software to restart.

When the restart is complete, verify that the plug-in was correctly licensed:

8. Sign in to System Manager.
9. Under Plug-ins, select the LPR plug-in.
10. Click Edit Settings.
11. Check the Licensing Status field. If the number of cameras bound to the plug-in is less than or equal to the number of licensed
cameras and the Licensing Answer matches, the status will be valid.

12. If more cameras are bound than are licensed or there is another problem with the Licensing Answer, the Licensing Status
field will display “invalid”.

If more cameras are bound to the plug-in than are licensed for
Premium LPR, the plug-in will ignore any cameras in excess of
the number of LPR cameras purchased.

13. If necessary, unbind cameras and restart the 3VR software, then re-check the Licensing Status.

Configuring Per-Camera Plug-In Settings

After binding the plug-in to cameras (step 3.2), links to edit camera-specific settings will appear under Bound Cameras for each camera.
Click a link (for example Edit “17. Garage West”) to edit the settings for that camera.

The following settings must be configured for each camera
bound to the LPR plug-in:

Setting Text Size

In the Text Size tab of the Edit Settings dialog, resize the orange
box until it is approximately the height of license plate characters in the underlying video feed.

This is especially important for license plates with wide borders. The positioning of the box in the video player is irrelevant.
This is especially important for license plates with wide borders.
The positioning of the box in the video player is irrelevant.

For best results, wait until a car enters the field of view,
then click the pause button () to freeze the video on the current frame.

Setting Plate Angle

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.

Drawing Lanes (for Multi-Lane Cameras)

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:

Click the polygon icon (located below the video player).
Click the video player to begin drawing a lane. Each click of
the mouse will create a new line segment. To complete the
polygon, click the mouse at your start position (the initial
vertex).
The width of the lane should be approximately the width of
the back of a car as it appears in the camera view.
When the lane has been created, edit the Name of the lane
and make sure that the check box in the Enabled column is
checked.
Repeat for any remaining lanes appearing in the field of view.

The name of the lane will appear on license plate events captured by the camera.
Lanes may optionally be configured for cameras with only one lane appearing in the field of view, but they are required
for multi-lane cameras.
Once a lane (or multiple lanes) has been defined for a camera, any part of the field of view outside of the lanes will not
be analyzed for plates. Consequently, lanes can be used to define an exclusion zone for the LPR analytic. However, if
lanes are configured and then disabled, no plates will be captured - the analytic will not return to scanning the full frame
until the lanes are deleted.
Lanes should be drawn slightly larger than the width of a typical car as it appears in the camera view.
Only megapixel cameras should be configured with multiple lanes.

Setting License Plate Speed (Premium LPR Only)

In the Parameters tab of the Edit Settings dialog, edit the License Plate Speed setting. The options are:

Under 10 mph / 16 kph (default)
Under to 20 mph / 32 kph

Important

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.

Finalizing Configuration

Restart System Software


In the Configure panel, right-click the appliance name and select Restart 3VR Software. In the pop-up box that appears, click Restart to proceed. Wait 1-2 minutes for the software to restart.

Verify Successful Configuration

To verify that the LPR plug-in has been correctly configured, check for recent license plate events in 3VR OpCenter:

In 3VR OpCenter, click the Monitor tab to go to the Monitor panel.
Click camera numbers to select the cameras bound to the LPR plug-in.
Click the arrow below the camera selector to open the event type drop-down menu.
Select [ ]License Plate to display events of that type.
Click OK.
If the plug-in has been correctly configured, license plate events will appear in the Monitor panel as they occur in real-time.

Verify that License Plate events are being generated correctly on all cameras bound to the plug-in during configuration.

Fine Tuning Plug-In Performance with Optional Settings

The remaining settings in the Edit Settings dialog should only be modified from their defaults if LPR results are unsatisfactory.

Text Size: Size Tolerance


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.
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).

Parameters: Minimum Track Time for an Event

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.

Parameters: Confidence Threshold

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.

Parameters: Armed Duration

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.

Parameters: Event Thumbnail Options

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.

Advanced: Use Artifact Removal

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).

Advanced: Compensate for License Plate Borders (Standard LPR Only)

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.

Advanced: Noise Sensitivity Threshold (Standard LPR Only)

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.