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# 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.
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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