Carrida Camera Program User Documentation

Revision: 1.4
Date: 2019-05-23
Contact: support@carrida-technologies.com
Copyright: 2017-2019 Carrida Technologies GmbH, Ettlingen, Germany
Author: Carrida Support

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Table of Contents

1   Introduction

Carrida is a software library for Automated License Plate Recognition (ALPR) in images. The Carrida Camera integrates an imaging and processing device, together with the Carrida 4 engine into a compact license plate reading sensor.


Typical applications of the Carrida Camera include:

  • Parking lot management
  • Vehicle ticketing/management
  • Automatic barrier opening
  • Vehicle counting
  • Law enforcement applications
  • Traffic planning (count vehicles, map traffic to geographic regions)
  • Traffic flow monitoring

Carrida offers the following features and benefits:

  • Easy to configure
  • Support for State/Country recognition
  • Supports license plates with two rows
  • Supports license plates with stacked characters
  • Robust against illumination, contrast, noise, and rotation


For further details and information see also the related documents:



A list of abbreviations used throughout this document:

ARM64
Stands for processors with the v8 AARCH 64-bit instruction set.
ARM
Stands for processors with the v7 ARM 32-bit instruction set.
ALPR
Automatic License Plate Reader.
dB
Decibel, in the Carrida documents used to describe a relative sensitivity (gain) value in cameras.
fps
Frames per second.
FOV
Field of view.
HW
Hardware.
LP
License Plate.
mA
Milli-Ampere, one 1/1000 th of an ampere.
ms
Millisecond, one 1/1000 th of a second.
OSD
On-screen display
PC
Personal Computer.
PK
Product Key (for software licensing).
px
Pixel. The smallest unit of resolution in an image. For example, VGA images are made up of 640x480 pixels.
ROI
Region of Interest, typically a marked area in an image.
SDK
Software Development Kit.
SW
Software.
x86
Stands for Processor Architectures with the Intel instruction set. 32-bit hardware.
x86_64
Stands for Processor Architectures with the Intel instruction set. 64-bit hardware.
VC
Vision Components GmbH.
Image symbols used in this document
Symbol Meaning
Note Sign Points to especially important aspects of the manual or the software.
Hint Sign The lightbulb highlights the hints and the ideas that may be helpful.
Warning Sign This warning sign alerts of possible pitfalls to avoid. Please pay careful attention to sections marked with this sign.

2   Quick start with the Carrida Camera

Once the camera is connected to your local network, it can be accessed using a web browser. Enter the provided IP address in the address bar of your browser (i.e. Chrome, Firefox, Opera, etc.) and the Carrida login page will open. A username and a password are required to sign in.

The Carrida User Interface offers four different user profiles: administrative, basic user, setup and viewer. The main difference between these profiles is the level of access to configuration and system settings. Factory Login credentials are as follows:


Administrator: Basic User: Setup: Viewer:

username: admin

password: secret

username: user

password: simple

username: setup

password: setup

username: viewer

password: pass

Access to all settings. Has the authority to add, delete and edit other users. Access to the most commonly used settings. Access to view live image streaming and reading results. Has the authority to change the ROI and classifier settings. Access to view live image streaming and reading results. No authority to change any parameters.

tt

To switch between User modes, click on the User button in the upper right corner of the interface.

Administrators have access to all amera, system and configuration settings.

We recommend not to change those configuration settings that are visible in administrator mode unless necessary.


Note

Note Sign

All graphical images will display the interface under admin mode.

2.1   Configure areas for reading and brightness control

ROI, short for Region of Interest, refers to the area in which some processing is done. There are two different types of ROIs used by the Carrida Camera:

  • the ALPR detection ROI to define where plates are to be detected
  • the ALPR brightness control ROI to define in which area the camera needs to adjust the brightness of the video stream.

Note

Note Sign

  • The ALPR detection ROI is drawn as a yellow polygon.
  • The ALPR brightness control ROI is drawn as a green polygon.

How the ROIs are displayed, and how to configure them is explained in the following table.

Live view Camera settings Server settings
t1 t2 t3

The OSD on the Live result page continuously displays a live image stream.

The yellow polygon represents the ALPR ROI.

The polygon can be adjusted in Settings, in the Interface page of the camera.

Both ROI for brightness control and ROI for ALPR detection can be defined in the Settings page.

The green polygon represents the Brightness control ROI.

The Brightness control settings are only applied to the area inside this polygon. This allows you to optimize the control over areas where it is required and ignore unwanted effects.

It is recommened to limit the brightness control ROI to the image area where the vehicles might actually move through the screen.

The ROI found in Engine represents the ALPR detection ROI.

It is displayed as yellow polygon. License plates will only be detected within this area.

It is recommended to make this ROI as small as possible.

View in Live results tab. ROI changes in Settings -> Camera ROI changes in Settings -> Engine


Hint

Hint Sign

Resize the polygons by clicking on any of the highlighted corners and drag/drop it to the desired position. When finished resizing, click on the Apply button.



Hint

Hint Sign

The ALPR detection ROI should be larger than and enclose the brightness control ROI, in order to achieve better performance.



2.2   Display results

Two pages in the camera user interface are used to display reading results either as a live video stream with a graphical overlay or in the form of a table:

  • the Live result page displays live images with reading results and updates the latest results in a compact table view.
  • the Text result page displays the results in a tabular form. Clicking on a list entry opens the associated image, which can also be downloaded. It is also possible to export the entire list as a CSV or an XLS document.

The result list can be limited to a certain amount of entries and/or have a time limitation. In the image above, the list is limited to 100 entries or the last 24 hours. When one of those conditions is met, the entry will be removed from the list. In cases where multiple recordings have been made and the list is too long, the user can move through the entries by using the Go to page button.

Overlaid on processed images are the ALPR reading results. They consist of:

  • state of vehicle registration,
  • state recognition certainty,
  • vehicle number plate,
  • number plate recognition confidence,
  • character recognition confidence.
./images/Image08.png

Processed image with an overlaid reading result.

In the example image above, AT stands for the state in which the vehicle is registered, and it is recognized with 68% confidence. W _ _ 4 3 3 is the vehicle number plate, recognized with 100% confidence. The confidence of recognition is displayed above each character; in this case, it is 100%.

3   Carrida Home

Entering the IP address of the camera in any web browser opens the login page:


./images/1_login.png

Login page of Carrida Camera Configuration


Submitting a valid username and password opens the homepage as illustrated in the image below.

./images/1_home.png

Homepage of Carrida Camera Configuration


Located in the upper right corner of the homepage is the User menu, which allows you to easily switch between user profiles.


The camera information section of the home page displays a compact overview of the current software version and classifier information on the camera.

Classifiers are files which are used to enable ALPR for a specific country or region. They provide additional information about plate specifics, i.e. size of characters, font style, plate dimensions etc. Information about which classifier is currently in use is listed in the camera information section.


The bottom of the page contains navigation links to different sections of the camera interface for quick access. Hover the mouse pointer over the icons to obtain a short description of the section functionality.

4   Live Result

The main purpose of the Live Result page is to verify the camera operation and configuration settings in real-time. To accomplish this, a live image stream from the camera is displayed on the Live results page, together with some additional information, such as reading results, confidences, etc. The details of this OSD can be configured, see Section Engine.

In addition to the video stream of the camera, the latest nine reading results are listed in the table on the right side of the page in order to provide a quick overview.

The yellow polygon overlaying the image represents the ALPR ROI. The camera will only process the plates which are detected inside of this area. The polygon can be adjusted on the Settings page, under the Engine tab.

./images/2_liveresult.png

5   Text Result

On the Text Result page, reading results of the camera are displayed in a table view. The table consists of:

  • a Timestamp with the date and the time when the plate was detected.
  • License plate information.
  • the Confidence for the given license plate recognition.
  • the detected Country of the vehicle license plate.
  • the Confidence for country recognition.

Note

Note Sign The result table is generated only when the webpage is accessed. To update the table, press the Reload button on the right bottom side of the page.



The number of results which are stored in the table is configurable through the History List Length (max 10000 entries), and History Hour (max 10000 hours) input fields at the bottom of the page.

Note

Note Sign History List Length and History hour will, by default, be set to 0.

When either the defined time limit or maximum number is reached, the oldest results are discarded, very similar to the operation of a ring buffer.


./images/3_textresult.png

ALPR Text results.


The list can be searched by any given information (plate number, date, time, etc.) by entering a string in the search field in the right upper corner of the page.

By either typing a page number in the GoTo Page field or clicking on the arrow next to the field, quick navigation through a large table is possible.

The contents of the table can be exported as a CSV and an XLS file by clicking on the buttons on the top left side above the list (see image above).


The right side of the page is reserved for images related to table entries. To display an image related to a reading result, click on the desired entry in the list. Individual images can be downloaded by clicking on the Download button above the image.

Right below the image, related actions and their states are listed. This provides information about which concrete action was defined for this reading result and if the action was successfully performed or not.

6   ACCESS Configuration

The ACCESS configuration page of the Carrida camera provides the tools to define what the camera has to do when a license plate has been detected. For example, an action could send the image and license plate string to a ftp server when matched with an entry of the Blacklist.

The ACCESS configuration page provides two tabs (Actions and Lists), which are used in conjunction to set up the camera as needed:


Lists
provide the means to define which license plates can trigger actions. Three categories of lists allow a more fine-grained control, a Whitelist, Blacklist and Ignorelist can each have their own associated actions. Each category supports import from and export of the data, as well as the addition of single list entries directly in the web interface.

Actions
tell the camera what to do when a specific event, happens. Actions can be triggered either by general events, e.g. the detection of a new license plate, or by specific events related to lists, or related to external trigger lines. Actions instruct the camera what to do when a specified event takes place. They allow the user to make full use of the I/O capabilities of the camera, including the network interface, I/O lines and the internal flash storage. As mentioned above, specific Whitelist match/mismatch, Blacklist match/mismatch and Ignorelist match/mismatch events may be used to trigger actions. In this case, the action will be executed when a plate from the list is detected (match), or when a plate is detected but is not on the list (mismatch).

./images/5_actions.png

Access control configuration page.


6.1   ACCESS lists

The three access lists available on the camera allow you to specify three classes of license plates, which can perform their own actions. when a license plate matches one of the lists. License plate entries may either be defined as full strings, defining only one specific license plate or with patterns (regular expressions) to match a whole set of strings.

The three types of Access Lists of the Carrida camera are:

  • Whitelist,
  • Blacklist
  • Ignorelist.

These lists can contain either specific license plates (BAD1234) or more general patterns for license plates (BA*) which match a larger set of license plate strings. These patterns are called Regular expressions, and theyare explained in detail in Section Regular Expressions below.

Every time the camera reads a new license plate from the video stream, it compares this plate string with all entries stored in each of the lists. If an entry matches, a previously defined action, if specified, is triggered and performed.


There are three types of events associated with the actions:
  • Events are considered to be "Read events" when the camera recognizes any LP
  • "NoRead events" occur when NO plates are detected between limitations set in Settings-Trigger. For example, if Start and Trigger timeout are defined and no valid plates are detected, the camera will perform an action defined in this section. Triggers are explained in detail in Section Trigger
  • "Low confidence read (LCR) events" - a Low confidence read event is created when the plate is read but the confidence level of the reading is lower than set in the parameter Limit of Low Confidence. This type of event is used to collect low-quality readings for further analysis.

./images/4_listcat.png

Each of the three lists is connected to a certain, possible action (match or mismatch of the plates from the list). That means that, by putting a certain license plate number on the list, the user can define which actions will be triggered if the plate is detected (match) or what happens if the plate is not detected (mismatch).

A list entry contains at least the plate number, but optionally also a date range and time range within which the match is to be accepted as being valid.

There are two ways to create or update the lists: they can either be created directly with a dialog in the camera web interface or they can be imported as text files from the PC. The latter method is more efficient if a large number of entries has to be created or if an external database of license plate entries (e.g. employees of a company) already exists and needs to be exported to the camera.

Both methods for access list creation are described in the following paragraphs.




Manual creation of a list entry

A new list entry can be directly created using a dialog in the camera's web interface as explained in the following table.

The first entry in the dialog box is the plate number. When Always enabled is turned ON, a match will not be restricted to a specific time range. When Always enabled is turned OFF, time and date limits apply. These can be defined through the date and time fields below.

This time window can be defined through the start and end date, start and end time, and on individual days of the week (marked with So, Mo, Tu, We, Th, Fr, Sa). By default, the time span is set to 24/7, Monday to Friday, for a month from the current date.

In the example on the right side, Monday-Friday is checked, meaning that if an LP is detected on any working day between the set dates, a certain action will be triggered.

After finishing the list, click on Add (the green plus button) and Save.

ls

Note

Note Sign Each plate can have multiple date/time windows attached (e.g. Monday 8am-12am and Wednesday 2pm-5pm). Use the Add button to attach a new definition to the plate. After all definitions have been made, use the Save button to store the entry for this license plate in the access list.




Import of list files into the camera

If a larger number of license plates has to be imported into one of the access lists of the camera, the import of a text file with definitions may be more convenient. The external text file has to be formatted as described in the following paragraphs. This can be done either automatically or by using a simple text editor.

Open any text editor to create a file and save it any_name.txt. Only text documents can be imported. Enter the information according to the formatting rules and save the file. On the ACCESS page under the List tab, click on Import and select the newly created document from your PC.

During import of the textfile, all entries are checked for validity. All valid entries will be displayed on the screen after the file is loaded. If needed, entries can be edited directly in the table.

When the list is finished, click on Upload to export the list to the camera.

2s



6.1.1   Formatting rules for external files


When importing external files, the following naming rules apply:
  • Every list entry must be placed in a single, separate line without blank spaces.
  • The entry order must be license plate; date window(s); or license plate; date window(s); time window(s)
  • Time window definitions are optional, but if given, they must be defined for every date window.
  • Plate number, date and time must be separated with semicolons (;).
  • When listing multiple dates/times separate them with a comma (,).
  • Date format: YYYYMMDD-YYYYMMDD, with no space between the numbers.
  • Time format: HH:MM-HH:MM. Time is always defined in combination with the date and a symbol (0/1) for the preferred day of the week.
  • Days of the week are represented with zeros and ones (0-not active, 1-active) written inside brackets starting with Sunday, ending with Saturday. For example, "0111110" non-active days are Sunday and Saturday, represented with zeros (0).
  • The number of dates set must be equal to the number of time restrictions ( W223344;20170101-20170101,20170102-20170102,20170103-20170103;03:00-04:00(0111110),03:00-04:00(0111110),03:00-04:00(0111110) ). If there are more dates than time restrictions (and vice versa) the definition will be perceived as invalid.


Example: W223344;20170101-20170125;03:00-04:00(0111110) an action will be taken if the vehicle with plate number W223344 is detected from 01.01.2017 (00:00) until 25.01.2017 (23:59) between 03:00 and 04:00 on any day of the week, except Saturday and Sunday (0111110).


Practical examples and descriptions for the rules:

  Example Description
Only plate number W223344 Actions will be taken when a vehicle with this plate number is detected.
Plate number and date   Date format:YYYYMMDD-YYYYMMDD, no blanks.
W223344;20170925-20170926 Actions will be taken if the plate is detected on a date inside set limitations ( 20170926<=[current date]<=20170925).
W223344;20170925-20170926,...,20170529-20170629 Multiple dates can be set, separated by a comma defined in one line, without blanks.
Plate number, date and time   Time format: HH:MM-HH:MM(0111110); 1 and 0 represent days of the week, starting from Sunday(0) till the last day Saturday(0), 0 meaning not active, 1 meaning active.
W223344;20170925-20170925;03:00-04:00(0111110) Time must be set in combination with the date.
W23344;20170925-20170925,201701012-20171112,...;03:00-04:00(0111110),05:00-06:00(0111110 ),...

When there are multiple dates, if time is set for one date it must be defined for all the dates or the limitation will be found invalid.

In this example, two dates with their respective times are set where date(1) 20170925-20170925 is combined with time(1) 03:00-04:00, and date(2) 20170112-20171112 is combined with time(2) 05:00-06:00 and so on.


To trigger actions when any plate is detected, upload a combination of symbols !* to a list class (i.e. permanent list).

Example:
If " !* " is on the permanent.txt list, and for this list, a positive matching action Store is enabled, the program will store all detected plates. pc

6.1.2   Regular Expressions

Regular expressions are used to conveniently define patterns for license plates or groups of license plate strings.

Carrida uses a powerful set of regular expressions, of which the most important details are described in the following paragraphs.


Note

Note Sign Regular expressions can be used in the dialog for list entry of the camera, or in the list text files which are imported. In both cases, a license plate number which is made up of a regular expression must be preceded with a "!" character, e.g. !B DE*



Hint

Hint Sign Details to all features of the Carrida regular expression syntax can be found here: https://www.boost.org/doc/libs/1_61_0/libs/regex/doc/html/boost_regex/syntax/perl_syntax.html



In Carrida regular expressions, all characters match themselves (example: A is always A, B matches B etc.) except for some special characters:

.
[]
{}
*
+
?

The '.' character matches every single character. E.g. the regular expression

G.23456

will match

G123456, or
GU23456, etc.

(In the above expression, the "." is matched by 1 or U respectively)



A character range is defined by a list of characters enclosed in []. For example [A-D] will match any single character in the range 'A' to 'D'. This character range may also be defined as [ABCD].

An atom is defined as being a character or character range.

A single atom can be repeated with the * , +, ?, and {} operators.



The * operator will match the preceding atom zero or more times, for example the expression

A*B

will match any of the following:

B
AB
AAAAAAAAAB


or the expression

A[BC]*D

will match

AD
ABCD
ACCCBBD

(between A and D, the characters B and C as defined by the atom [BC] may be repeated any number of times.


Note

Note Sign A regular expression beginning with a * is invalid because the * operator does not precede any other atom. Use the combination .* instead!


The + operator will match the preceding atom one or more times, for example the expression

A+B

will match any of the following:

AB
AAAAAAAAB


But will not match:

B


The ? operator will match the preceding atom zero or one time, for example, the expression CA?B will match any of the following:

CB
CAB

But will not match:

CAAB


An atom can also be repeated with a bounded repeat, where the number of allowed repeats is defined as part of the regular expression:

A{n} Matches 'A' repeated exactly n times.

A{n,} Matches 'A' repeated n or more times.

A{n, m} Matches 'A' repeated between n and m times inclusive.



For example:

A{2,3}

Will match either of:

AA
AAA

But neither of:

A
AAAA


Following are some useful examples for regular expressions and use cases:



To match any license plate string of at least length 1:

.+


Match license plate strings which consist of digits only:

[0-9]+


Match all taxis, under the assumption that taxis have a license plate string that ends with TX:

.+TX


Match all license plates that start with a letter and end with a digit:

[A-Z]+.*[0-9]+


Match all license plates from the Carrida company, assuming that their license plates consist of a CAR string and a following 3 number digit (like CAR001):

CAR[0-9]{3}


Note

Note Sign When making a list by using regular expressions in either the camera dialog or the text file used for import, the definition for the regular expression must always start with a "!" character.

6.2   Actions

Once the camera detects a license plate, it checks whether some action has to be taken based on this reading. This event could be

  • detection of a license plate of any string,
  • no detection of a license plate after a trigger signal within a specified time interval
  • detection of a specific license plate as defined in one of the lists,
  • detection of a specific license plate which does NOT match a list

More specifically, there are several types of events which can trigger actions:

  • Read events occur when the camera detects any license plate. It will then trigger actions defined for this category.
  • NoRead events occur when NO plates are detected between limitations set in Settings-Trigger. Triggers are explained in detail in Section Trigger
  • LCR events - a Low Confidence Read event is created when the plate is read but the confidence level is lower than set in the parameter Settings-Access control-Limit of Low Conf.
  • Whitelist match, Blacklist match and Ignorelist match (the license plate is found in one of the lists).
  • Whitelist mismatch, Blacklist mismatch and Ignorelist mismatch (the license plate is NOT found in one of the lists).

Starting from the Access page of the camera as shown in the following image, actions for each of the event categories can be set up. The following possible actions can be triggered:

  • Ftp Upload
  • Ftp Database
  • Store
  • Digital out
  • Serial
  • TCP
  • HTTPPUT
./images/5_actions.png

Access actions categories.


To add an action, first choose the category for which the action is to be added (Read/NoRead/LowConfidenceRead, Whitelist match/mismatch, blacklist match/mismatch or Ignorelist match/mismatch). After clicking on the ADD button, a specific action can be selected and configured in the dialog window, as shown below.

Different actions require different sets of parameters, all of which are explained in detail in the following sections.

./images/6_addaction.png

All actions which create dynamic results (filenames, HTTP strings, etc) offer the option to use placeholder variables.

Placeholders are used to specify the text the camera needs to generate from the reading result. Placeholders are dynamic types of information (like the current license plate string, even the current image may be specified).

Placeholders are selected by their name, which is placed between two percentage (%) symbols (see the example below). When an action is performed, placeholders will be substituted with their current value (e.g. the actual license plate string).



Example:

A placeholder for the license plate is %LP%, for the date is %DAY% %MONTH% %YEAR%, level of confidence for plate recognition is %CONF%.

The camera detected a vehicle with number plate W223344 on the 03.08.2017, with confidence 98%.

The dynamic text

Detected %LP%(%CONF%) on %DAY%/%MONTH%/%YEAR%.

would result in the actual created text

Detected W223344(98) on 03/08/2017.

A complete list of placeholders can be found in the Section Placeholders for naming patterns.


The following sections describe all possible actions that can be triggered by the camera.


6.2.1   Ftp Upload

f

Ftp upload is the most commonly used action. It is used to save image files of detected plates to a remote ftp server.

Enter the Host ftp servers IP address in form of sftp://xxx.xxx.x.xxx/[...].

Username and Password of the ftp server must be written in the form of: [username]:[password]. Example: for the username "user123" with the password "pass123" the correct form is: user123:pass123 .

Naming patterns are used to include specific reading information (date, time, plate...) in the file name. How to use and format names using patterns read in the Section Placeholders for naming patterns.

Images can be uploaded as follows:

  • Empty file
  • Full image
  • License plate image only

Empty file sends files with no images. This saves memory and increases the upload speed.

Image quality refers to the compression rate, it can be set from 1 to 100%, 1 being the maximal compression level which will produce images with the lowest quality and 99 being the minimal compression level with the highest image quality. We recommend setting this parameter to 65-70%.

Enable the action by sliding the Enable button to the right side, until a blue ON button is revealed


6.2.2   Ftp Database

4

This action will create and automatically update a text file on the ftp server.

Enter the Host ftp servers IP address in form of sftp://192.168.3.127/[...].

Username and Password of the ftp server should be written in the form of: [username]:[password]. Example: for the username "user123" with the password "pass123" the correct form is user123:pass123 .

Filename stands for the name of the database to be updated (created) with a new result string.

Naming patterns define the database entry string. How to form naming patterns read in Section Placeholders for naming patterns.

Enable the action by sliding the Enable button to the right side, until a blue ON button is revealed


6.2.3   Store

5

This action will store data in the internal memory of the camera.

Define the name of the Folder and the Postfix.

The Postfix field is the part of the name which will be appended after and the extension. This field can also be left empty.

Minimal free disc space required to be available on the camera to save the file is defined by Free space parameter. If there is less space available on the camera than defined here, the files will not be saved.

Enable the action by sliding the Enable button to the right side, until a blue ON button is revealed


6.2.4   Digital Out

6

This action will produce a digital output for a specific time period (Output duration).

Select which Output pin will be activated by the action.

Output duration defines the duration of the output signal in ms.

The Invert signal option can be disabled/enabled.

Enable the action by sliding the Enable button to the right side, until a blue ON button is revealed


6.2.5   Serial

8

Construct a message using Naming patterns and this message will be sent through the serial port of the camera.

Enable the action by sliding the Enable button to the right side, until a blue ON button is revealed


6.2.6   TCP

9

Write a message for the action using TCP with text and placeholders (Section Placeholders for naming patterns).

Enter the IP address of the receiver of the TCP address and the Port used to send the TCP message.

Enable the action by sliding the Enable button to the right side, until a blue ON button is revealed


6.2.7   HTTPPUT

ö

The HTTPPUT method puts a file or resource at a specific URL. If there is already a file or resource at that URL, PUT will replace that file or resource.

Define the URL and enter the credentials, username and password for the URL.

In patterns define the name of the file using the guidelines in Section Placeholders for naming patterns

Enable the action by sliding the Enable button to the right side, until a blue ON button is revealed


7   Settings

The Carrida camera provides the necessary configuration parameters to optimize its operation for different application scenarios. Modification of settings for image acquisition, sensitivity of detection, etc. ensures that the camera can be adjusted to avoid common problems like

  • poor image resolution, if the plate is too far from the camera,
  • motion blur,
  • poor lighting and low contrast due to overexposure, reflection or shadows.

In order to optimize the image acquisition of the camera, it is important to understand how parameter settings influence the resulting image quality and reading performance.

7.1   Overview

The Settings page divides the available camera parameters into several logical menus, which can be opened and closed by clicking on the triangle next to the menu name.

As shown in the image below, the settings are divided into 7 tabs (Camera, LED Flash, Trigger, Engine, Mode of operation, Access Control and Display Information). The tabs are opened by clicking on the right-pointing arrow. In the example image, all menus except Display Information are closed.

./images/8_settingsdropdown.png

Access actions categories.



Hint

Hint Sign There are three types of parameters, which can be configured:

  1. Drop-down menus with a predefined list of options.
  2. Input fields where users can put in values within a certain range
  3. Enable/disable options. They can be changed by clicking on either the green checkmark (enabled) or a red cross mark (disabled).

All changes are confirmed by clicking on the Apply button; a green circle with a white, right-pointing arrow.



The following Sections describe each of the menus in detail.

7.2   Camera

The Camera settings page is used to optimize the imaging performance of the camera. It allows the user to modify brightness control parameters and define gain settings and exposure times. How to adjust these parameters properly, and what they mean is described in Section Camera.

Gain and shutter options directly impact image acquisition. Gain, expressed in dB, represents the camera's sensitivity to light and shutter speed measures the exposure time in microseconds.


What does the green polygon represent?

The area inside the green polygon is called the brightness control ROI. It defines the area within which the camera measures and corrects the image brightness by controlling exposure time and gain within a certain range.

It is recommended to limit the brightness control area to the actual image region where license plates are expected to be visible. This maximizes the effect of the control parameters and allows the camera to achieve the best image quality in all possible scenarios.

How to adjust the brightness control polygon and for more information about the ROI see Section Use Brightness control.



The following four parameters define the limits for analog gain and exposure time as used by the camera's automated brightness control algorithm. When these limits are set to extreme values, the camera may be able to capture optimally exposed images, but at the cost of reduced image quality.

For example, if the gain is allowed to become too high, images may become too noisy for detection, or if the exposure time is becoming too high, motion blur may be visible.



7.2.1   Minimum Gain (dB)

Gain controls the amplification of the signal from the camera's sensor, and thus its overall sensitivity. A higher gain setting boosts the image brightness at the cost of introducing noise. A lower gain setting, therefore, creates better images.

The Minimum Gain parameter defines how low the camera can go with the gain control when it tries to adjust the image brightness. For best image quality it is recommended to set this parameter to 0.



7.2.2   Maximum Gain (dB)

The Maximum Gain parameter defines how high the camera may go with the gain control when it tries to adjust the image brightness. The higher the camera my go, the more noise could be introduced into images, thus making them harder to read.

We recommend a maximum gain value of 10 for the Carrida Camera.



What is the shutter resp. exposure time?

A camera shutter is a mechanism that lets the light in through the lens onto the sensor of the camera. It has two states- open and closed, and the time it stays open is measured in microseconds (μs) in the Carrida camera.

Fast shutter speed means the shutter will open and close quickly, limiting the amount of light that hits the sensor. A slow shutter speed resp. long exposure time means that more light can pass through to the sensor, producing brighter images.

The maximum allowed shutter time gives you control over motion blur, should vehicles move too fast. Shorter shutter time reduces the motion blur of the moving vehicles.


Hint

Hint Sign
As a general recommendation, the following exposure (shutter) times are advised:
  • shutter time of 100-3000 μs on highways, for high-speed vehicles
  • shutter time of 100-5000 μs in urban areas, for medium speed vehicles
  • shutter time of 1000-20000 μs in parking situations, for slow vehicles


7.2.3   Minimum Shutter

The Minimum Shutter parameter defines, in μs, how short the shutter time can become when the camera tries to adjust the image brightness. The Minimum Shutter time must always be lower or equal the Maximum allowed shutter time.

The lowest possible value is 10 μs, but we recommend to set a value of 50 μs, especially when the camera is located indoors.


Note

Note Sign If the Minimum Shutter time is set too high, the camera may not be able to adjust the image in very bright illumination conditions (e.g. if the Sun is directly behind the camera and its light is being reflected from license plates).



7.2.4   Maximum Shutter

The Maximum Shutter time defines, in microseconds, how long the shutter can stay open when the camera tries to adjust the image brightness. The Maximum Shutter time must always be higher or equal to the minimum allowed shutter time.

If the Maximum Shutter time is allowed to become too high (e.g. allowing it to get to 20000 microseconds in an urban environment), vehicles that move too fast are likely to become blurred. In order to avoid this problem, the Maximum Shutter time needs to be reduced. See the recommendations above for suggested values.

If the Maximum Shutter time needs to be reduced, in order for the camera to achieve an acceptable image quality, try to adjust:

  • the maximum allowed gain (if possible), or
  • try to increase the power of the built inLED flash by configuring more LED current and/or
  • a longer flash time (see Section LED Flash for a description).


How to estimate the maximum allowed exposure time:

The maximum possible exposure time can be calculated from the viewing geometry and image resolution. The basic principle is that a vehicle should not move more than 1 px in the image during the exposure time, at maximum possible speed.

It is possible to either compute this value exactly using measurements of the visible street section, viewing angles, etc. or it can be approximated.

By measuring the time (T) it takes a vehicle from top to bottom or left to right of an image- whatever time is shorter- and the image resolution in this direction (i.e. the number of pixels), the maximum allowed exposure time in ms can be computed as follows:

exposureTime(ms) = 1000*(T/resolution)



7.2.5   Low Resolution

The Carrida camera sensor can operate in two resolution settings

  1. low resolution of 640x480 pixels and
  2. high resolution of 1280x960 pixels.

The lower resolution mode allows the camera to achieve a higher processing framerate, so that vehicles which move faster through the camera field of view are captured with higher accuracy. The disadvantage of the lower resolution mode is that the camera can read license plates only up to a distance of about 5 meters.

The high-resolution mode enables the camera to read license plates up to a distance of about 9 meters, at the cost of a slower reading rate.



7.2.6   Image Rotation (deg)

In situations where the camera only has an oblique view onto the street, it might be preferable to rotate the camera image so that the license plates appear horizontal. This is not a requirement for good readings, but it can improve recognition quality.



7.2.7   Brightness control Region

The Brightness control region is the area enclosed in the green polygon shown in the live image when the Camera menu is selected in the Settings page:

./images/8_settingscamera.png

The Brightness control area defines the image region used by the camera to continuously analyze and adjust the image brightness. To this end, the camera tries to set the current shutter time and gain in a way that the image has the best possible average brightness and has neither too many overexposed pixels nor is it too dark.

The parameters which control the allowed amount of overexposed and underexposed pixels and are set with the parameters BC max bright pixels, described in Section BC max bright pixels and BC min Correct pixels, described in Section BC min correct pixels.


Resizing the Brightness control polygon
Click, drag and release the corner of the polygon. Click on Apply next to the Brightness control region option under the image to save changes.
example


In this case, the camera is mounted in front of the gate. The polygon captures the path that the vehicles might take so that the brightness control area is set to the smallest possible area.

Hint

Hint Sign We recommend setting the brightness control area to the smallest possible area so that the camera can optimize the image brightness for the relevant image region. A good idea is to synchronize the BC area with the ALPR ROI, this can be done by pressing the blue Sync button in the right lower corner of the live image.

./images/Image15_sync.png


7.2.8   Use Brightness control

This setting turns the automatic brightness control on or off. Our recommendation is to leave this parameter enabled at all times, as it will enhance image quality and produce better ALPR results.



7.2.9   BC max bright pixels (%)

During automatic exposure control, the camera counts all the 'good' pixels within the brightness control area. Good pixels are neither too dark nor overexposed.

In cases where there are too many overexposed pixels, the camera will change its exposure settings to make the image darker. The correct pixel counts are indicated as a percentage (0-100) relative to the image size.

Hint

Hint Sign What to do if the license plates are constantly overexposed?

If the license plates are constantly too bright, the percentage value of maximum saturated pixels needs to be reduced, so that the camera tries to decrease the count of those pixels on its own.

Example: reduce the value from 5% to 3% and observe the effect on the live image stream.

Another possible cause for constantly overexposed images is a Minimum Shutter time which is set too high, so that the camera is not allowed to darken the image more. See Section Minimum Shutter time on how to reduce the Minimum Shutter time.



7.2.10   BC min correct pixels (%)

All pixels with brightness below the grey value threshold 90 will be considered not bright enough resp. too dark. All pixels with the grey value of over 200 will be considered overexposed. Pixels that are between low and high brightness levels are considered to be 'good' pixels.

The correct pixel count is indicated as a percentage (0-100) relative to the image size. If there are too many overexposed and/or underexposed pixels the camera will adjust exposure settings to get the correct pixel amount to reach, at least, the minimum level set here.

Hint

Hint Sign What to do if the license plates are constantly too dark?

If the plates are constantly too dark, the value of minimum correct pixels needs to be increased, so that the camera can try to increase the number of those pixels.

Example: modify the value from 3 to 5% and observe the effect in the live image.

Another possible cause for constantly underexposed images would be setting either Maximum Shutter time or Maximum Gain too low, so that the camera is not allowed to brighten up the image more. See Section Maximum Shutter time on how to increase the Maximum Shutter time or Section Section Maximum Gain on how to increase Maximum Gain. Optionally also the LED flash power could be increased, see Section LED Flash for more information.



7.3   LED Flash

The Carrida camera has a built-in IR flashlight which can be controlled through the LED flash settings. It is recommended to have the flash turned on at all times to optimize the contrast of license plates. In addition to the LED, the Carrida camera is also equipped with a daylight blocking filter which is tuned to the LED wavelength. This feature reduces the influence of sunlight as well as reflections from the headlights of vehicles.


The relative strength of the LED light is controlled via two parameters:
  • The LED flash duration, how long the LED flashes when triggered by the camera. The flash duration may be as short as 10 microseconds and at most as long as the camera shutter time, but never longer than that.
  • The LED current, which defines the total power of the flash. The flash current is set in mA and may range from 150-1500 mA. Flash current setting of less than 150 mA will turn the flash off.


./images/9_settingsledflash.png

LED Flash settings on the Configuration screen.



7.3.1   Enable Flash

Enabling the flash will turn the IR LED flash on.

We recommend leaving the flash enabled at all times.



7.3.2   Flash Duration (µs)

The Flash Duration parameter defines the duration for which the flash is actually emitting light when triggered by the camera. The flash is exactly synchronized with the beginning of image acquisition by the camera. Its duration may be shorter than the current exposure time, but it will never be longer.

E.g. if the current exposure time by the camera is 500 µs and the flash time is set to 800 µs, it will nevertheless be cut off at 500 µs.

As the flash duration is set to shorter times, its ability to freeze vehicles in motion gets better. For example, shorter flash durations are desirable when dealing with vehicles that are moving fast. In a typical city environment with up to 70 km/h (45 mph), a flash duration of 1 ms would be a good choice.



7.3.3   Flash Current (mA)

Independent of the flash duration, the current which flows through the LEDs is another means to control their brightness. The more current is sourced through the LEDs, the brighter they become.

The LED controller circuit covers a current range from 150 to 1500 mA, a value of < 150 mA turns the LEDs off.


It is recommended to set the current in a range from 500 mA to 1000 mA, so that
  1. it is bright enough even for LP at larger distances
  2. the flash is strong enough to illuminate license plates even in the presence of vehicle lights. This becomes especially important when the Carrida camera is used indoors.

Note

Note Sign

If the duration of the LED flash is set to 150 mA or less, the flash will be turned off by the controller circuit.



7.4   Trigger

The Carrida camera offers several options to control its operation through the use of digital I/O lines. These I/O signals allow the user to limit the time when the camera actually reads in combination with some basic timing parameters. E.g. the camera can be set up to start reading for 5 seconds after the trigger signal from a ground loop has been received.

By also creating an associated action, the camera may execute a command if a LP has been read, or even if no LP has been detected at all (see Section Actions for further explanation of actions and events).


There are five different trigger modes available as shown in the following table:

Overview of Carrida cam trigger modes
Free_run read without considering any trigger signals
Single_Line read as long as the trigger line is active
Start_Stop start and stop reading when the defined I/O lines are activated
Start_Time start reading for a defined time upon receiving a trigger
Start_Sequence start reading at a defined number of imaǵes after the trigger signal

Note

Note Sign In the following Section, the term session will be used to describe the time between the start signal by a trigger and the end of a triggered period, which may either be signaled through another I/O line or by a timer.

A session is the only time period in which the camera reads license plates. During an open session, it operates as defined in the reading modes, e.g. like in the non-triggered parking mode, etc.



The trigger setup is controlled in the Settings page, in the Trigger menu as shown in the image below. The following paragraphs explain the possible trigger modes, their setup and operation in detail.


./images/11_settingstrigger.png

Trigger configuration page.



Hint

Hint Sign The electrical requirements for digital IO and triggering are defined in the VC pro Z Series Operating Manual.



7.4.1   Trigger mode

The different trigger modes as described above are each configured using their own set of parameters:

  • The Setup section lists the parameters which are related to the mode and are used for its configuration
  • The Start section describes the signals which will start a session
  • The Stop section describes the condition which will end a session

After choosing the mode from the drop-down menu, press the Apply button to activate the trigger mode and set the parameters as needed.



fr Setup: No other parameters need to be defined for this mode.
Start: The session starts simultaneously with the camera. No external signal is required to start the camera.
Free run should be the default mode when an external trigger is unavailable or not required.
sl

Setup: Define Start trigger line, Start trigger polarity.

If Start trigger polarity high is enabled, the session will start when the input signal is transitioning from low to high. If Start trigger polarity high is disabled, the session will start when the input signal is transitioning from high to low.

Note: The Noread Interval parameter is being ignored in this mode.

Start: The session will start when the signal from Start trigger line is received.
Stop: The session is ended when the signal on the input line changes its state again.
ss

Setup: Define Start trigger line, Start trigger polarity. In addition, define Stop trigger line and Stop trigger polarity. If Start trigger polarity high is enabled, the session will start when the input signal is transitioning from low to high. If Start trigger polarity high is disabled, the session will start when the input signal is transitioning from high to low.

Note: The Noread Interval parameter is being ignored in this mode.

Start: The session will start when the signal from Start trigger line is received.

Stop: The session stops and result images are generated when the signal from Stop trigger line is received.

In case a new trigger signal is received while the old session is still open, the camera closes the old session and opens a new session immediately.

st

Setup: Define Start trigger line, Start trigger polarity. and Trigger timeout (ms). If Start trigger polarity high is enabled, the session will start when the input signal is transitioning from low to high. If Start trigger polarity high is disabled, the session will start when the input signal is transitioning from high to low.

Note: The *Noread Interval* parameter is being ignored in this mode.

Start: The session will start when the signal is received.

Stop: The session lasts for a defined time period (set in Trigger timeout). After the time passes the session is closed.

In case a new trigger signal is received while the old session is still open, the old session will be extended to a new timeout period.

NOTE: in this case, the camera does NOT generate NoRead actions for the interrupted session.

sseq

Setup: Define Start trigger line, Start trigger polarity. and Sequence length in frames.

If Start trigger polarity high is enabled, the session will start when the input signal is transitioning from low to high. If Start trigger polarity high is disabled, the session will start when the input signal is transitioning from high to low.

Note: The NoRead Interval parameter is being ignored in this mode.

Note: Trigger signals are ignored while a session is open.

Start: The session will start when the signal from Start trigger line is received.
Stop: The session lasts for the defined sequence length.


7.4.2   Noread Event Interval (frames)

This parameter specifies the interval of images without any plate readings before defined no-read actions are executed. This parameter is only used in freerun mode.



7.4.3   Start Trigger Line

This parameter defines a start trigger line which begins the session.

When the input line on the camera is activated/triggered, it will send a signal to the camera to start the session.

An overview of active input and output pins can be found in System settings.



7.4.4   Start Trigger Polarity High

This parameter defines the active polarity of the input line in order to start a session.

If Start trigger polarity high is enabled, the session will start when the input signal is transitioning from low to high.

If Start trigger polarity high is disabled, the session will start when the input signal is transitioning from high to low.



7.4.5   Stop Trigger Line

This parameter defines a stop trigger line which ends a session.

When this pin is activated/triggered it will send a signal to the camera to end the current session.

An overview of active input and output pins can be found in System settings.



7.4.6   Stop Trigger Polarity High

This parameter defines the active polarity of the input line in order to stop a session.

If Stop trigger polarity high is enabled, the session will stop when the input signal is transitioning from low to high.

If Stop trigger polarity high is disabled, the session will stop when the input signal is transitioning from high to low.



7.4.7   Trigger Timeout (ms)

This parameter defines time duration (in milliseconds) of one session. The session starts when Start trigger line signal is received and ends after the defined time passes.



7.4.8   Sequence length (frames)

This parameter defines the number of frames which will be processed in one session. The session starts when Start trigger line signal is received, and the session ends after the defined number of frames are acquired and processed.



7.5   Engine

The Engine page controls all parameters necessary to set up the actual reading of license plates. The provided default values will usually result in good general reading results, but they can be modified to tune the camera operation to specific situations.


./images/12_settingsengine.png

7.5.1   Reading mode

The Carrida engine can operate in several performance modes, which are differentiated by recognition/processing speed and reading accuracy. The faster modes offer a higher reading speed on the camera at the cost of lower reading accuracy and vice versa. The Carrida camera offers the following possible reading modes, ordered from fastest to slowest:

  • Fastest
  • Fast
  • Standard
  • High
  • Best

The modes are explained in detail in the table below.




  Mode Description
mo Fastest Fastest possible processing speed with lower recognition quality than in other modes. Recommended for open traffic when recognition speed has priority.
Fast Fast processing speed with slightly better recognition quality than in the fastest mode. Also intended for open traffic situations.
Standard A good compromise between speed and reading performance, recommended to be used in most situations.
High High mode is about half the speed compared to fast mode (e.g. from 50 ms to 100 ms), the reading accuracy of high mode is typically 2-3% better than the fast mode.
Best The best possible reading quality. Can be up to two times slower than in the fast mode. At the same time, reading confidence will be about 3-4% better.


7.5.2   Min letter height (px)

Defines the minimal height of characters, in pixels, which are to be recognized. The camera will only accept characters larger in height than set with this parameter. This value should not be less than 8 pixels.

Use this parameter if license plates above a minimum size should be read- e.g. by enforcing a value of 16 px, license plates which are too far away from the camera will be ignored.



7.5.3   Max letter height (px)

Defines the maximum height of characters, in pixels, which are to be recognized. The camera will only accept characters smaller in height than set with this parameter.



7.5.4   Max plate angle (deg)

If there is a chance that the vehicles will appear rotated, relative to the camera. This parameter allows to adjust the range of accepted angles.

Best results are achieved when Max plate angle is between 5° and 20°, we recommend a maximum value of 40°.

Try to avoid rotated LPs by installing the camera so that LPs appear level.



7.5.5   Minimal plate confidence (%)

Minimum plate confidence refers to the minimum confidence level at which the camera will accept the plates as valid. All readings with a confidence smaller than this value will be ignored.



7.5.6   Maximum Plates

Refers to the maximum number of plates that can be detected in a single image. Setting it to 0 means that an unlimited number of plates can be detected.



7.5.7   Minimum contrast

This parameter defines the minimal contrast to differentiate foreground (characters) from the background (the license plate itself). Reducing this parameter increases both the reading performance and the processing time. Modifying the minimum detected contrast may help read LPs in difficult lighting situations, at the cost of slower reading time.

It is recommended not to modify this parameter and use the default value provided by the camera unless absolutely necessary.



7.5.8   Scale Height/Width

The values are provided in percent of the original image size (100 = original size).

Scaling means resizing an image in percentage relative to its original size, with separated scales for width and height. This is done before any other processing takes place. It is, therefore, overhead to the initial processing, but still may reduce the total processing time if the image size is overall reduced.

Scaling may help in situations where you have a view from the top or side at a large angle. The LP will be distorted, and to adjust for that, it is possible re-scale the opposite side to a value < 100. This would compensate for the original perspective effects.



7.5.9   Search inverted

Search inverted is an option that controls the way the camera engine will search for the LP in terms of contrast of the characters (black-on-white or white-on-black contrast) as follows:


Search inverted Description
Disabled The camera will only search for plates with a bright background and dark characters (i.e. black symbols on white background). This is the fastest mode and it is recommended if only this type of LP can occur.
Search The camera will only look for white-on-dark license plates when no dark-on-white license plates have been detected. This option is a reasonable compromise between speed and detection rate. It is still recommended to turn it on only when necessary.
Always The camera will, in addition to black-on-white LP, always look for white-on-black plates. This option is slow and should only be used if absolutely necessary.

./images/Image27.png

Example of inverted and regular plates.



7.6   Mode of Operation

Depending on the application of the Carrida camera, different methods of image acquisition and processing might be needed.

For example, the camera should only read and transmit unique license plates for access control applications, where a server should not be inundated with constant results of the same license plate reading.

In order to provide good starting points of parameter sets, the camera offers several setups which are tuned to specific use cases.

The way the camera handles sequences of images, duplicate readings or small reading errors, is configured using several control parameters which are described in the following sections.



./images/13_settingsmodeofoperation.png


As mentioned above, the Mode of Operation menu allows you to set up the camera for different operating scenarios quickly:

  • single processing mode
  • parking mode
  • offline
  • freeflow

The modes listed below are different in the way the minimum number of correct readings, buffer size etc. is set up, but the camera is not restricted to these modes. By changing individual parameters, the user can adjust the camera operation to a specific scenario.

The following table describes the default setups and their use case, the sections following after that describe each control parameter in detail.



./images/13_settingsmodeofoperation_mode.png
Mode Usage Output
Single The camera reads every single image as quickly as possible. Each input image is considered unrelated to adjacent images. Every single detected license plate.
Parking

This mode is designed for access and parking control systems. Each vehicle number plate is required to be detected at least the number of times defined in the Minimum Detections parameter.

If Minimum Detections value has been reached, the LP will be available as a detection, and it will be ignored until it is no longer visible.

Unique license plates.
Offline

In this mode, the results are available with a delay of about 25 frames. The reading quality is the best in this mode as the engine has more frames to analyze before producing results. The main purpose of this mode is to detect LP with the best possible quality without the need for real-time operation.

Note: Not recommended for normal use, it is typically used to collect LP images for training.

Unique license plates.
Freeflow

This mode is designed for freeflow operation. Considering the Minimum Detections parameter, the camera tries to read as quickly as possible. Results may become available with a delay of up to 15 frames.

The difference to Parking Mode is the larger Buffer Size which increases reading quality at the cost of a higher delay until a LP is transmitted.

Unique license plates. Longer delay until LP are read


Note

Hint Sign The number of parameters for the mode of operations is limited in the WebGUI of the camera. The REST API allows control over all parameters.



7.6.1   Minimum Detections

The Minimum Detections parameter controls how many readings of the same license plate will be made until a definite result is produced. The result transmission takes place only after this number of readings.

A new reading is accepted as valid if:

  • The number of character differences to previously read strings is not greater than Maximum character Mismatch, see Section Maximum character mismatch.
  • If it is detected inside the ALPR region of interest

Note

Hint Sign Minimum Detections delays the transmission of images and readings because the camera is set up to wait until this number of correct readings has been made.



7.6.2   Maximum characters mismatch

Maximum plate mismatch refers to the maximum amount of characters allowed to be different before two readings are considered to be different.

The useful range for this parameter is 1-3.


7.7   Access control

Access control is always enabled by default, which means that the consideration of the blacklist, whitelist and ignorelist and their related user-defined actions is always on.

./images/14_settingsaccesscontrol.png


7.7.1   Limit of Low Conf(%)

This parameter is used to set a limit under which the reading confidence will be considered low, but still valid. The lower confidence limit must be equal to/greater than the Min Plate Confidence.

The typical use of this parameter in conjunction with the Low Confidence Read action is to detect and store low quality (= confidence) readings for further analysis or retraining.



Note

Hint Sign The following ftp features are deprecated and should not be used anymore, they will be removed from Carrida Version 4.3.2 on.**



7.7.2   Download Lists from Ftp

If this parameter is enabled, the server will try to download lists from a previously specified FTP server by using the credentials defined in the next two parameters. This feature can be used to update the ignore-, black- or white lists from an external server.



7.7.3   List FTP Server

FTP Server address to download list files from will be specified in this parameter.

The address has to be written in the following format: sftp://xxx.xxx.xxx.xxx



7.7.4   List FTP Server Credentials

FTP Server credentials have to be given in the following format: username:password


Example:For the username "user123" with the password "pass123" the correct form is user123:pass123 .

7.8   Display Information

The set of parameters in the Display Information menu allows you to configure the way information from the camera will be visualized.

Display properties are modified with the first 9 parameters of the Display information menu:

  • HUD Size
  • Hud Position
  • Text Info
  • Draw Info
  • Draw Time
  • Draw Date
  • Display Shutter
  • Display Gain
  • Display Camera Framerate

Visual properties of ALPR result images can be modified through the following parameters:

  • Display reading framerate
  • Draw plate
  • Draw state
  • Draw character confidence

Enabling/disabling any of these options will take immediate effect on the image display in the web interface of the camera as well as all stored images.

The following sections describe the display options in detail.


./images/15_settingsdisplayinfo.png


7.8.1   HUD Size

This parameter affects the size of the On Screen Display (OSD). Select between small, medium or large display.



7.8.2   HUD Position

The HUD can be positioned on the top/bottom left side, or top/bottom right side of the OSD.



7.8.3   Text Info

Text information is an optional arbitrary string which can be displayed as part of the OSD. Typically this field describes the location or use of the camera ('exit North').

The display of this text field is enabled with the Display info flag, see Section Display Info



7.8.4   Display Info

Display Info when enabled (checked), displays Text information defined in the text parameter above.



7.8.5   Display Time

When enabled, the current time will be overlaid on the result images and over the live stream images.



7.8.6   Display Date

When enabled, date information will be overlaid on the result images and over the live stream images.



7.8.7   Display Shutter

By enabling this parameter, the average shutter speed resp. exposure time (in microseconds) will be displayed.



7.8.8   Display Gain

If enabled, information about the camera analog gain (in dB) will be displayed.



7.8.9   Display Camera Framerate

Framerate refers to the number of individual frames (images) per second (fps) which are currently grabbed from the camera sensor. Not all of the grabbed images are being processed. Depending on the processing load of the camera, some images may be skipped, resulting in the actual Reading Framerate - see next Section below.



7.8.10   Display Reading Framerate

Enabling this parameter allows the information about the camera's processing framerate to be displayed in the OSD. This rate corresponds to the actual number of readings which the camera is currently performing.

This number depends on the image size (low- or high-resolution), the ALPR ROI size (smaller is better), and other settings.



7.8.11   Draw Plate

When enabled, the camera will overlay the reading results over detected LPs (see Example).



7.8.12   Draw State

If Draw State is enabled, the name of the detected state, as well as the reading confidence, will be shown.

This parameter will only be activated in combination with Display Plate. If Display Plate is not enabled, the state information will also not be displayed.


Example:

Enable Display plate and Display state.

A vehicle with a license plate W554433 is detected.

As a reading result, the SW overlays "AT 68 W554433 100" onto the result image.

"AT 68%" AT stands for Austria, the state, and 68% is the percentage of recognition confidence for the state. "100" stands for 100% confidence that the plate read is "W554433"(see Example).



7.8.13   Draw character confidence

By enabling Draw character confidence, the confidence of recognition for each character will be overlaid above the vehicle number plates.



Shown in the table below are examples of overlaying plate, state and character confidence.


Example:

Image (A) displays an LP image with the the state and plate visualisation enabled.

In the image (B) plate, state and character confidence visualization is enabled.

Image (C) is generated with only plate visualization enabled.

vz


7.8.14   JPEG Compression Level

JPEG compression reduces the size of the images significantly - this results in faster data transfers (e.g. ftp uploads) and reduces the bandwidth consumption of the camera to display the live images in its user interface.

The level of compression can be set on the scale from 1 to 100, whereby a lower number means a higher compression rate with a resulting lower image quality.

Our recommendation is to set the JPEG compression level to 65, as this is a good compromise between image quality and required network bandwidth. If the camera is connected to a slow network, the JPEG compression factor can be reduced to values of 50 and less.


Note

Note Sign It is a typical sign of a slow network connection if live images from the camera are not fully displayed in your browser (if the lower part of the images is either sporadically or constantly missing from the live stream).



8   System Configuration

The System Configuration page allows you to set general system related properties of the camera. As shown in the image below, the following Configuration settings can be modified:

  • Network - set the IP address of the camera, network mask, gateway IP and DNS IPs.
  • Time - turn the network time protocol on or set the timezone.
  • Users - create, delete or change user profiles.
  • Classifier - upload a classifier and view the supported state list.
  • System - view trigger input/output activity and the camera SW version.

./images/16_configuration_network.png

8.1   System Actions

The System actions button is located on the upper left side of the screen. As illustrated in the image above, clicking on it reveals a drop-down menu. System Actions is a group of settings and parameters used to perform maintenance tasks on the camera:


./images/20_configuration_systemsettings.png


8.1.1   Restart the camera and Reboot system

Restarting and rebooting the camera is possible by clicking on the Restart ALPR or Reboot system buttons.



8.1.2   Download Logs

All stored camera logs can be downloaded by clicking on Download logs. The log files wll be packed and compressed into a .ZIP file.



8.1.3   Save Configuration

Complete camera configuration, inclding the classifier files, can be stored locally by clicking on Save configuration.

Saving the configuration is a three-step process, consisting of collecting the files, creating an archive and storing it on your PC, as illustrated in the image below.

./images/20_configuration_save.png


8.1.4   Import Configuration

Previously saved configuration settings can be imported into the camera by clicking on Import configuration. Importing may take some time.

The user can choose which system settings to import by enabling or disabling the features. After the server is done importing the settings, a confirmation window will appear listing the restored settings and notifying the user of a reboot.

The following settings can be imported:
  1. Server configuration
  2. Classifier
  3. Network Configuration
  4. Time Configuration
./images/22_configuration_import.png

Importing server and network configuration



Note

Note Sign

Import Server Configuration imports all camera Parameters and List settings.



8.1.5   Change Camera Password

The root password of the camera can be changed with this setting.



8.1.6   Factory Reset

The last option on the System tab is the Factory reset.

This option is used to reverse the camera configuration back to factory settings.


8.2   Network

This page is used to modify the following Network settings of the camera:

  • DHCP
  • IP Address - set the IP address of the camera
  • Network mask - set the network net mask
  • Gateway IP - set the gateway IP address
  • DNS IP - set the IP address
  • DNS IP 2 - second IP address, if needed

Any of these parameters can be changed by clicking on the Edit button, as shown in the image below.


Hint

Hint Sign

The Dynamic Host Configuration Protocol (DHCP) is a network management protocol used on TCP/IP networks where the DHCP server dynamically assigns an IP address and other network configuration parameters to each device on the network. A DHCP server enables computers to request IP addresses and networking parameters automatically from the Internet service provider, reducing the need for a network administrator or a user to manually assign IP addresses to all network devices. In the absence of a DHCP server, a computer or any other device on the network needs to be manually assigned an IP address.

If DHCP is turned OFF, manual network settings need to be provided to allow networking on the camera.


./images/16_configuration_network+edit.png

System configuration for network settings.


Warning

Warning Sign

A warning dialog will appear if the serial number of the imported configuration and the actual camera are different. In this case, the user will be asked to choose whether to proceed with the configuration.


8.3   Time

In Time settings, the time or the timezone can be set and the NTP server list can be customized.

Clicking on the Edit button brings the user to the following window with the list of active NTP servers:


./images/17_configuration_time+edit.png

The camera can use any of these servers to synchronize its internal clock.

In order to manually set the camera's time, NTP has to be turned OFF - NTP can be enabled/disabled by clicking the slider on top of the dialog.

You can use the Set Time field to manually enter date and time and thus set the camera's internal clock.

Note that NTP is, by default, turned on.


8.4   Users

The Carrida camera allows you to manage three different user profiles, which are differentiated by the level of access to configuration and system settings. The profiles are administrative, user, setup, and viewer, they are described in the following table:


The camera's default sign in credentials are:

  Username Password Description
Administrator admin secret Immediate access to all settings.
Basic User user simple Access to the most commonly used settings.
Setup setup setup The same access level as "viewer", plus changing the ROI and the classifiers.
Viewer viewer pass Permission to view reading results and live image streaming.

The addition of new users, deletion of old ones or the password changes can be performed in the user menu.


Note

Note Sign

The Users dialog is only accessible in advanced mode.


After clicking on the Create new button, a dialog box will appear as shown in the image below, it allows you to create a new user profile on the camera.


./images/18_configuration_users+edit.png

Note

Note Sign

The camera password is not the same as user passwords.


8.5   Classifier

Classifiers are files which contain state- and country-specific information about license plates. This information can, for example, be the size and the font of letters and numbers, the alphabet used etc.

Classifiers are created specifically for different regions of the world (Europe, USA, Thailand...) by Carrida.

The Carrida camera can store classifiers as a part of its firmware, this list of classifier files may be updated and expanded by the user.

The Classifier Menu shows you the currently stored classifier list on the camera under the Available Classifiers section (see also the next image below).



Note

Note Sign

Only one classifier may be active on the camera at a time, but a classifier can contain information about an arbitrary number of countries (e.g. all countries of the EU).



The Classifier menu of the Configuration menu allows you to upload new classifiers, delete old ones, and activate any classifier, which is stored on the camera.

The dialog to modify classifier parameters can be called by clicking on the blue pencil icon on the right side of the Classifier menu:

./images/19_classifier_edit.png

8.5.1   Switching Classifiers

As mentioned above, the camera can store a large number of classifiers as part of its firmware, and those classifiers can be switched anytime.


./images/19_configuration_classifiers_switch.png

Switching classifiers


A click on the drop-down menu (illustrated in the image) will display a complete list of supported states. By selecting a new country or region from the list and then pressing the green apply button, the classifier will be activated.



8.5.2   Uploading Classifiers

New classifiers can be uploaded by clicking on the green upload button, which brings up a new dialog window where a new classifier can be dropped and uploaded, as illustrated below. Alternatively, a click on the green button on the top right bottom of this dialog opens a new dialog that prompts you for a classifier file from your PC.


./images/19_configuration_classifiers_upload.png

Upload classifiers


While uploading a new classifier, the user can opt for deleting all previous classifiers by turning on the option Delete other classifiers.

After uploading a classifier, the camera firmware will automatically restart in order for the changes to take place.


8.6   System

The system menu displays information about firmware software versions and all available digital input and output lines and their respective states.


./images/20_configuration_system.png


8.6.1   Libraries

Versions and build dates of the Carrida software libraries.



8.6.2   Inputs/Outputs

Outputs and Inputs parameters show which lines are active and which are inactive.



9   Placeholders for naming patterns

This section describes all the special keywords that can be used as placeholders in messages used within actions. See Section Actions for a description of actions.

During the creation of a message as part of an action, placeholders will be replaced with dynamic values as defined by the placeholder, e.g. the actual license plate string for the placeholder %LP%.

A thorough explanation of how to use the naming patterns can be found in the Naming patterns section.


Listed in the table below are all the keywords and their descriptions:


Placeholder Description
   
"%LP%" This keyword will be replaced by the license plate value string.
"%LP_WS%" This keyword will be replaced by the license plate value string containing found white spaces.
"%STATE%" This keyword will be replaced by the state string.
"%CONF%" This keyword will be replaced by the confidence value string.
"%CONF_STATE%" This keyword will be replaced by the state confidence value string.
"%NUM_ROWS%" This keyword will be replaced by the count of rows of license plate as a string.
"%REGION%" This keyword will be replaced by the region string.
"%REGION_CITY%" This keyword will be replaced by the city string.
"%REGION_SHORT%" This keyword will be replaced by the region short value string.
"%ENDING%" This keyword will be replaced by the state value string.
"%ENDING_SHORT%" This keyword will be replaced by the state value string.
"%COL_PLATE%" This keyword will be replaced by the color of the plate as a string.
"%COL_CHARS%" This keyword will be replaced by the color of characters as string.
"%POS_X%" This keyword will be replaced by x position in the image of the left upper corner of the license plate as a string.
"%POS_Y%" This keyword will be replaced by y position in the image of the left upper corner of the license plate as a string.
"%POS_W%" This keyword will be replaced by the width of the license plate in the image as a string.
"%POS_H%" This keyword will be replaced by the height of the license plate in the image as a string.
"%YEAR%" This keyword will be replaced with the year string. (When a license plate is detected)
"%MONTH%" This keyword will be replaced by the month string. (When a license plate was detected)
"%DAY%" This keyword will be replaced by the day string. (When a license plate is detected)
"%HOUR%" This keyword will be replaced by the hour string. (When a license plate is detected).
"%MINUTE%" This keyword will be replaced by the minute string. (When license plate is detected).
"%SECOND%" This keyword will be replaced by the seconds string. (When a license plate is detected).
"%FRACSEC%" This keyword will be replaced by a fraction of seconds string. (When license plate was detected).
"%COMMA%" This keyword will be replaced by a comma.
"%BR_ON%" This keyword will be replaced by '('.
"%BR_OFF%" This keyword will be replaced by ')'.
"%CR%" This keyword will be replaced by the carriage return sign.
"%LF%" This keyword will be replaced by the line feed sign.
"%FULL_IMG%" This keyword will be replaced by base64 encoded full image string.
"%LP_IMG%" This keyword will be replaced by base64 encoded cropped LP image string.



Example:

The camera has detected a German plate "TEST123" on 01.01.2017 at 10:15:20. You can form a naming pattern as follows:

" License plate value: %LP% from %STATE% " the form will be displayed as : " License plate value: TEST123 from DE "
" Filename_%HOUR%_%MINUTE%_%SECOND%.jpg " the form will be displayed as : " Filename_10_15_20.jpg"