Number Plate Recognition

Number plate recognition detects and reads license plates on vehicles.

Configuration Parameter Description
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.
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.
MaxInputQueueLength Can be used to place a limit on latency.
MaxPlatesPerFrame The maximum number of number plates that you expect to appear in a single image or video frame.
MinCharHeight The minimum height of the main characters on the number plate.
MinRead The minimum number of consecutive frames in which a number plate must be visible before a result is generated.
MinValidScore The average character score required for a number plate to be recognized.
NumParallel The maximum number of video frames to analyze simultaneously.
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.
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.
SampleInterval The interval at which frames are selected to be analyzed.
SegmentDuration The maximum duration of a record in the SegmentedResult or SegmentedResultWithSource track.
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 one record, describing the analysis results, per detected number plate, per video frame. No
DataWithSource NumberPlateResultAndImage

The same as the Data track, but each record also includes the source frame.

No
Event NumberPlateEvent (Deprecated) Media Server creates a record in this track when a number plate appears or disappears. Yes
Result NumberPlateResult Contains one record, describing the analysis results, for each recognized number plate. When the same number plate appears in many consecutive frames, Media Server produces a single result. Yes
ResultWithSource NumberPlateResultAndImage

The same as the Result track, but each record also includes the best source frame.

No
SegmentedResult NumberPlateResult (Available only when processing video). Contains one or more records, describing the analysis results, for each recognized number plate. The maximum duration of records in this track is limited by the parameter SegmentDuration, so multiple records are created with the same ID when a number plate remains in the scene for longer than this duration. Yes
SegmentedResultWithSource NumberPlateResultAndImage

(Available only when processing video). The same as the SegmentedResult track, but each record also includes the best source frame.

No
Start NumberPlateResult

The same as the Data track, except it contains only the first record of each event.

No
End NumberPlateResult

The same as the Data track, except it contains only the last record of each event.

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

NumberPlateResultAndImage

The same as NumberPlateResult records, with the following additional fields.

Field name Type Description
image ImageData The source frame

NumberPlateData

Field name Type Description
readregion PolygonData A polygon describing the region that contains the main read.
plateregion PolygonData A polygon containing the entire 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 OutputAlternativeResults 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.
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.

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.

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