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To configure queue detection tool, do as follows:

  1. Select the License plate recognition (VT) object. 

  2. Configure parameters.

    ParameterDescription
    EnableEnable/disable detection tool.
    Record Objects trackingIf you need to enable recording of metadata, activate this parameter.
    Analysis modeSelect detection tool working mode: standard or neural.
    Country nameSelect one or more countries for ANPR.
    Decoder mode

    Select a processing resource for decoding video streams. When you select a GPU, a stand-alone graphics card takes priority (when decoding with NVidia NVDEC chips). If there's no appropriate GPU, the decoding will use the Intel Quick Sync Video technology. Otherwise, CPU resources will be used for decoding.

    Frame size change

    Analyzed framed are scaled down to a specified resolution (1920 pixels on the longer side). This is how it works:

    1. If the longer side of the source image exceeds the value specified in the Frame size change field, it is divided by two.

    2. If the resulting resolution falls below the specified value, it is used further.

    3. If the resulting resolution still exceeds the specified limit, it is divided by two, etc.

    License typeSelect the current license type.

    Maximum LP width

    Minimum LP width

    Set the maximum and minimum width of the vehicle number plate as a percentage of the FoV width.

    The Minimum LP width parameter affects the CPU load as follows: the higher the parameter is, the higher the load.

    ModeChoose a processor to run detection on. In standard mode, detection runs on the CPU only.
    Number of framesSet the number of frames required for LPR/ANPR. This is though a necessary condition, but not sufficient for the first output. This condition delays LPR output. This parameter allows to increase the reliability of the results, as well as to hide false positives.
    Advanced image analysis

    If necessary, enable advanced image analysis – improves the quality of recognition under adverse conditions (for example, if the characteristics/settings of the camera do not fully meet the requirements, or in bad weather). The processing time of the frame increases by 20-30%, depending on its size.  Under normal conditions, this setting does not affect the quality of recognition

    Algorithm of recognition of distorted LP imageTo recognize the numbers at sharp angles with respect to the camera, activate this parameter.
    Contrast threshold

    Set the image contrast threshold. The default value is 40. On a high-quality image, increase this value to 50-60. If the image has poor contrast, lower this value. 

    LP advanced search algorithm

    If you expect different sizes of number plates within FOV, activate this parameter. This parameter accounts for max and min width of number plates, and, in some cases, may help increasing recognition quality and optimizing CPU load.

    Minimum similarity

    Timeout

    LP display quality


    To set up a number plate recognition event:

    1. Specify the minimum percentage of similarity between the recognition result and the corresponding number plate template, for positive LPR result. Use this parameter to filter the results by reliability.

    2. By default, a number plate recognition event is registered after a track containing a number plate disappears from FOV. You can set the moment of registration to a Timeout in seconds, or to reaching a similarity percentage specified in the LP display quality field. If both parameters are set to non-zero, the recognition event will be registered upon matching the first condition.

    The LP display quality parameter value must be no lower than the Minimum similarity value.

    Maximum number of recognition threads

    Specify the maximum number of recognition threads. If the value is 0, the recognition process will occur in the same thread that starts it.

    The cumulative value of this parameter across all NPR detection tools must not exceed:

    - the licensed number of recognition threads (check your license with the lsvpwcutility – please refer to manufacturer's documentation);

    - the number of CPU cores;

    - 100.

    Tracker Timeout

    Set a time interval in seconds after which the tracking of a vehicle is reset.

    Use this setting to eliminate double-triggering in such cases as, for example, another recognition of the same number after it has been obstructed for some time, and then reappears in scene.

    If you set Tracker Timeout to a value greater than a probable time of obstruction, the detection tool will not double-trigger.

    VodiCTL_VPW_DYNAMIC_ENABLE

    Enable/disable the number recognition dynamics (by default, the dynamics is enabled).

    If the parametr is enabled, then tracking is enabled, and the number is recognized by the set of frames. If the parametr is disabled, then tracking is disabled, and the number is recognized by each frame separately without taking to account the previous ones, and the quality can vary from 0 to 100%.

    VodiCTL_VPW_DYNAMIC_OUTPUT_PERIOD

    Time period (in microseconds) over which the recognition result is to be displayed to the user. This parameter can be used only if the VodiCTL_VPW_DYNAMIC_WITH_DUPLICATE parameter is set.

    VodiCTL_VPW_DYNAMIC_OUTPUT_TIMEOUT

    The minimum time required to monitor the license plate (in microseconds) before displaying the recognition result to the user. This parameter can only be used when the “Dynamic” mode is on. In this mode, the trajectory of the vehicle is monitored, and the user does not immediately receive the recognition result of the license plate, but after the time specified for this setting. In this case, the first recognition result will be replaced by the result of higher quality and subsequently displayed to the user. If parameter 0 is set for this value, the user gets the first result of recognizing the detected license plate.  After the time specified in this parameter expires, the monitoring of the trajectory of the license plate continues until it disappears from the frame.

    VodiCTL_VPW_DYNAMIC_WITH_DUPLICATE

    Enable/disable the periodic output of license plate recognition results.

    VodiCTL_VPW_IMAGE_BLUR

    The parameter for internal use. The recommended value to set is 13.

    VodiCTL_VPW_LOG_SETTINGS

    Enable/disable logging of all recognition parameters.

    VodiCTL_VPW_PLATE_FILTER_RODROPFACTOR

    The license plate filter coefficient by the so-called image density – ratio of white pixels to total pixels (second strategy). The type is unsigned. This coefficient is used for image thresholding and has the optimal values, which are determined by AutoSDK developers using their own test samples. The parameter is considered as a service one, and its value should be set according to the recommendations of technical support specialists.

    VodiCTL_VPW_PLATE_FILTER_ROFACTOR

    		The license plate filter coefficient by the so-called image density – ratio of white pixels to total pixels (first strategy). The type is unsigned. This coefficient is used for image thresholding and has the optimal values, which are determined by AutoSDK developers using their own test samples. The parameter is considered as a service one, and its value should be set according to the recommendations of technical support specialists.

    VodiCTL_VPW_PLATE_FILTER_SYMCOUNT

    Enable/disable the simple license plates filter algorithm by the minimum number of recognized symbols on them. If the algorithm is enabled (the value of the parameter is greater than 0), the base search for symbols on the prospective license plate (geometry, proportions) is performed. If less symbols are recognized on the prospective license plate than specified in this parameter, this prospective license plate is not considered a license plate. That is, the value of this parameter is the minimum characters that must be present on the prospective license plate when the basic algorithm is in use.

    VodiCTL_VPW_PLATE_STAR_MAX

    Maximum unrecognized symbols on the license plate, at which the result will still be considered the result of the recognition of the license plate.

  3. In the Preview window, you can set the detection zones:
    1. Select the Detection area object. 
    2. To select the area, move the intersection points .
  4. Click  to save changes.

The detection tool is now configured.


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