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# 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 | 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 in which you are reading number plates.
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 | HPE 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 number plate text.
platecenter | PointData | (Deprecated) The position of the center of the number plate.
plateregion | PolygonData | A polygon describing the position of the 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. HPE 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 HPE 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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