License Plate Parser (Edge)

Extracts license plate numbers locally from the license plates detected using the License Plate Detection and the Licence Plate Recognition models.

Overview

This node parses the output of "License Plate Recognition" model to extract the license plate information.

This node requires AI Model Node (Vehicle Detection model) -> Model Inference Node (License Plate model) -> Track Objects Node -> Model Inference Node (License Plate Recognition) prior to it in order to function properly.

Inputs & Outputs

  • Inputs : 1, Media Format : Raw Video
  • Outputs : 1, Media Format: Raw Video
  • Output Metadata : None

Properties

Property

Value

display_info

If true, LPR info will be drawn on video.

ex. true / false

objects_to_associate

Objects classes that should be considered on the LPR and vehicle association.

ex. car, vehicle, truck

Accepted formats:
object_label: any object of this type, with or without a classifier attribute. Example: car

object_label.class_type: any object of this type that has a specific classifier attribute. Example: car.red

object_label.*: any object of this type that has at least one classifier attribute. Example: car.* (this will match car.red, car.yellow, etc)

detection_buffer

Time (in seconds) that the License Plate must be present before reporting results in metadata.

ex. 1.0

rejection_buffer

Time (in seconds) during which objects that leave and re-enter the scene will be ignored. Increase to reduce duplicate alerts for a given object.

ex, 5.0

Metadata

Metadata Property

Description

nodes.<node_id>

License plate information as described in the JSON below.

<node_id> for License Plate Detection Nodes is of the form annotate_lpr_edgeX (ex. annotate_lpr_edge1)

"nodes":{
    "annotate_lpr_edge*":{
        "type":"annotate_lpr_edge",
        "license_plates_entered_delta":"<int>",
        "license_plates_exited_delta":"<int>",
        "license_plates_count":"<int>",
        "license_plates":{
            "<object_tracking_id>": {
                "plate":{
                    "type":"Plate",
                    "score":<float>,
                    "props":{
                        "plate":[
                            {
                            "value":"<license_plate_number>",
                            "score":<float>
                            }
                        ]
                    }
                }
            }
        }
    }
}

Format

Key

Type

Description

license_plates_entered_delta

Integer

Number of new license plates detected since last frame

license_plates_exited_delta

Integer

Number of license plates that left since last frame

license_plates_count

Integer

Total number of license plates in the view right now

license_plates

List of object IDs

Information about each detected and recognized license plate.

object_tracking_id : Unique identifier for a specific object, as specified by object.id property (see Track Objects Node

Please check the json example for more details.


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