Number Plate Recognition

Number plate recognition detects and reads license plates on vehicles.

This section describes the parameters that you can use to configure number plate recognition.

Configuration Parameter Description
BlackAndWhiteCamera (Deprecated) Specifies whether the source camera captures grayscale video.
Boldness The boldness setting to use for detecting the edges of characters.
CharHeightUnit The units used to specify the expected size of number plates (pixel or percent).
ExpectedRotation The expected amount of rotation (from horizontal, in degrees) for a number plate in the scene.
FreeformRegion The Region of Interest (ROI) to monitor for number plates, if the ROI is not rectangular.
Input The image track to process.
Integration The method to use to integrate multiple number plate reads into a single result.
Location The location(s) for which you are reading number plates.
LocationWithPriorities The locations for which you are reading number plates, and their relative priorities.
MaxCharHeight The maximum height of the main characters on the number plate.
MaxPlatesPerFrame The maximum number of number plates that you expect to appear in a single image or video frame.
MaxRead The maximum number of frames to use to read a single number plate, when Integration=moving.
MinCharHeight The minimum height of the main characters on the number plate.
MinRead The minimum number of frames in which a plate must be visible before a result is returned, when Integration=moving.
MinValidScore The average character score required for a number plate to be recognized.
NumParallel The maximum number of video frames to analyze simultaneously.
OutputAllIntResults (Deprecated) Specifies whether to return all results, when integration returns more than one result, all for the same plate in the image.
OutputAlternativeResults Specifies whether to return all results, when integration returns more than one result, all for the same plate in the image.
OutputUnformattedResults Specifies whether to include unformatted results in the output. These are results where the number plate exceeds the confidence score specified by MinValidScore, but does not match one of the expected formats.
PlateSizeUnit (Deprecated) The units used to specify the expected size of number plates (pixel or percent).
Region The Region of Interest (ROI) to monitor for number plates.
RegionUnit The units used to specify the position and size of the region of interest (pixel or percent).
RejectReadsWithInvalidGaps Specifies whether to reject number plate reads with gaps in the wrong place.
RepeatDelay The amount of time that must pass after a number plate leaves the scene, before the same number plate can be reported again.
SampleInterval The interval at which frames are selected to be analyzed.
Sensitivity The confidence level required to detect a number plate.
Type The analysis engine to use. Set this parameter to NumberPlate.

Output Tracks

Output track Type Description Output1This column indicates whether the information contained in the track is included by default in the output created by an output task (when you don't set the Input parameter for the output task).
Data NumberPlateResult Contains a record for each number plate that is detected. Multiple records are created if the same number plate appears in consecutive frames. No
DataWithSource NumberPlateResultAndImage Contains the same information as the Data track, but each record also includes the source frame. No
Event NumberPlateEvent Media Server creates a record in this track when a number plate appears or disappears. Yes
Result NumberPlateResult Contains a single record for each recognized number plate (the same number plate is likely to appear in many consecutive frames). This track only contains the best result from running number plate recognition and integration. Yes
ResultWithSource NumberPlateResultAndImage Contains the same information as the Result track, but also includes the best source frame. No

NumberPlateResult

Field name Type Description
id UUIDData A unique identifier to identify the number plate (there is one UUID per plate; records with the same UUID represent the same number plate in different frames)
numberplate NumberPlateData Information about the number plate
resultstatus String The type of result obtained (none/detect/read)
integrationstatus String

The status of integration at this record:

  • started integrating
  • still integrating
  • integration ended with no result
  • integration ended with result

NumberPlateEvent

Field name Type Description
id UUIDData A universally unique identifier to identify the number plate.
event TrackingEventData The type of event (begin/end), and the elapsed time since the number plate appeared.
resultstatus String The type of result obtained (none/detect/read)

NumberPlateResultAndImage

Field name Type Description
id UUIDData A unique identifier to identify the number plate (there is one UUID per plate; records with the same UUID represent the same number plate in different frames)
numberplate NumberPlateData Information about the number plate
resultstatus String The type of result obtained (none/detect/read)
integrationstatus String

The status of integration at this record:

  • started integrating
  • still integrating
  • integration ended with no result
  • integration ended with result
image ImageData The source frame

NumberPlateData

Field name Type Description
readregion PolygonData A polygon describing the region that contains the main read.
platecenter PointData (Deprecated) The position of the center of the number plate.
plateregion PolygonData A polygon containing the entire number plate.
binarizethreshold Integer (Deprecated) The binarize threshold used to read the number plate.
plateread String The characters read from the number plate
platetype String The plate type ("Regular" or "Square")
platetypecode String The number plate type code, which specifies the positions of subreads and logos in relation to the main characters.
country String The name of the country from which the number plate originates.
state String The state, determined from the number plate. This field is only used for some locations, for example number plates from the United Arab Emirates.
subread String The sub-read from the number plate. This field is only used for some locations, for example number plates from the United Arab Emirates.
vehicletype String The vehicle type (private, taxi, military, and so on), determined from the number plate.
score Integer The confidence score for number plate recognition, or for the integration process if this record is a result
alternativeresults String A possible alternative result. Media Server only includes an alternative result if integration produces two possible results and you set the OutputAllIntResults parameter to TRUE.
numreadframes Integer The number of frames that were analyzed to produce the result.
mincharheight Integer The minimum character height detected by ANPR for this result.
maxcharheight Integer The maximum character height detected by ANPR for this result.
sensitivityscore Integer The sensitivity score for this result. This value can be useful when setting the Sensitivity. This score must be higher than the Sensitivity for Media Server to consider the plate valid.
invalidgaps Boolean Specifies whether the result contains invalid gaps that would cause the result to be rejected if RejectReadsWithInvalidGaps=TRUE.
finaldata Boolean This field specifies whether the record is the final record in a series used for integration.
rawread String The characters read from the number plate by optical character recognition. This field can contain a different value to the plateread field because it shows the characters read from the plate before the expected plate formats are applied.
unformattedread Boolean Indicates whether the result is "unformatted" (does not match any of the expected formats). These results are normally rejected and only appear in the output when you set OutputUnformattedResults to TRUE.

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