License Plate and MMC Recognition (Cloud)

Recognize license plate numbers and make/model/color using Lumeo's cloud service for the license plates detected using the License Plate model.

Overview

This node uses a cloud based service to read license plates from vehicles that are detected using the Vehicle & License Plate models.

This node requires AI Model Node (Vehicle Detection model) -> Model Inference Node (License Plate model) -> Track Objects Node prior to it in order to function properly using the "LPR & Make/Model/Color" recognition mode.

Inputs & Outputs

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

Properties

Property

Value

geographies

Geographies that the license plates may belong to. Use this to optimize license plate recognition.

ex. us, us_ca

objects_to_track

Objects on which to perform License plate recognition. Unset means all.

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)

display_info

Display License plate (+ MMC) information on the video stream itself.

ex. true / false

recognition_mode

Recognition mode

"LPR & Make/Model/Color" (lpr_mmc) => Requires a Model Inference Node for Vehicle Detection and another one for License Plate Detection. We will only perform recognition once we find a valid association between a Vehicle and a License Plate.

"LPR Only" (lpr_only) => Requires a Model Inference Node for License Plate Detection. Will perform recognition attempts using the detected License Plate image crop.

"Make/Model/Color Only" (mmc_only) => Requires a Model Inference Node for Vehicle Detection Performs recognition attempts using the detected Vehicle image crop.

requests_buffer

The interval (in seconds) before perform the initial LPR request and between subsequent retries

ex. 1.0

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_lprX (ex. annotate_lpr1)

"nodes":{
    "annotate_lpr*":{
        "type":"annotate_lpr",
        "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>
                            }
                        ],
                        "region":[
                            {
                            "value":"<region>",
                            "score":<float>
                            }
                        ]
                    }
                },
                "vehicle":{
                    "type":"<vehicle_type>",
                    "score":<float>,
                    "props":{
                        "make_model":[
                            {
                            "make":"<make>",
                            "model":"<model>",
                            "score":<float>
                            }
                        ],
                        "orientation":[
                            {
                            "value":"<orientation>",
                            "score":<float>
                            }
                        ],
                        "color":[
                            {
                            "value":"<color>",
                            "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 the license plate, make, model & color of each vehicle.

object_tracking_id : Unique identifier for a specific object, as specified by object.id property (see Model Inference Node )

The "plate" and "recognition"` fields contents may not be present depending on the current recognition results.

Please check the json example for more details.


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