Configuration

LicensePlateRecognizerConfig Anatomy

LicensePlateRecognizer is configured entirely through a LicensePlateRecognizerConfig object with these components:

import degirum_vehicle

config = degirum_vehicle.LicensePlateRecognizerConfig(
    license_plate_detection_model_spec=detection_spec,  # 1. Detection model
    license_plate_ocr_model_spec=ocr_spec,             # 2. OCR model
)

1. License Plate Detection Model Spec

Specifies which model detects license plate regions and their bounding boxes.

Default: TFLITE/CPU model on @cloud inference host

detection_spec = degirum_vehicle.get_license_plate_detection_model_spec(
    device_type="HAILORT/HAILO8",
    inference_host_address="@cloud"
)

2. License Plate OCR Model Spec

Specifies which model extracts text from detected license plate regions.

Default: TFLITE/CPU model on @cloud inference host

ocr_spec = degirum_vehicle.get_license_plate_ocr_model_spec(
    device_type="HAILORT/HAILO8",
    inference_host_address="@cloud"
)

Model Specs Explained

A ModelSpec tells degirum-vehicle which model to load and where to run it.

Configuration Philosophy: You can configure models by explicitly specifying model specs (Options 2 & 3) or use the convenience method (Option 1) that automatically selects the right models for your hardware. Additionally, you can initialize from YAML files (Option 4) for production deployments.

You have four options to initialize the configuration:

Option 1: Use from_hardware() Convenience Method (Recommended)

The easiest approach - just specify your hardware and inference location. The model registry automatically selects the best detection and OCR models for you:

import degirum_vehicle

# Run on cloud CPU
config = degirum_vehicle.LicensePlateRecognizerConfig.from_hardware(
    "TFLITE/CPU",
    inference_host_address="@cloud"
)

# Create recognizer
lpr = degirum_vehicle.LicensePlateRecognizer(config)

Other examples:

# Run on local Hailo device
config = degirum_vehicle.LicensePlateRecognizerConfig.from_hardware(
    "HAILORT/HAILO8",
    inference_host_address="@local"
)

# Run on specific GPU
config = degirum_vehicle.LicensePlateRecognizerConfig.from_hardware(
    "TENSORRT/GPU",
    inference_host_address="localhost"
)

When to use: Most use cases - fastest way to get started without worrying about individual model selection.

Option 2: Use Model Registry Helper Functions

For more control, specify models individually using the registry helper functions:

import degirum_vehicle

# Get detection model spec
detection_spec = degirum_vehicle.get_license_plate_detection_model_spec(
    device_type="HAILORT/HAILO8",
    inference_host_address="@cloud"
)

# Get OCR model spec
ocr_spec = degirum_vehicle.get_license_plate_ocr_model_spec(
    device_type="HAILORT/HAILO8",
    inference_host_address="@cloud"
)

# Create config with explicit model specs
config = degirum_vehicle.LicensePlateRecognizerConfig(
    license_plate_detection_model_spec=detection_spec,
    license_plate_ocr_model_spec=ocr_spec
)

# Create recognizer
lpr = degirum_vehicle.LicensePlateRecognizer(config)

Parameters:

• device_type - Hardware accelerator (see supported hardware below)

• inference_host_address - Inference location: @cloud, @local, or AI server address

Supported Hardware:

See the complete list of supported hardware platforms.

When to use: When you need different hardware/hosts for detection vs OCR models, or want explicit control over model selection.

Option 3: Bring Your Own Models

For complete customization (using models outside the registry), create custom ModelSpec objects directly. See ModelSpec Documentation for details.

When to use: Custom-trained models, private model zoos, or models not in the official degirum-vehicle registry.

---

YAML Configuration (Option 4)

For production deployments and version-controlled configurations, initialize from YAML files:

license_plate_detection_model:
  hardware: "TFLITE/CPU"
  inference_host_address: "@cloud"

license_plate_ocr_model:
  hardware: "TFLITE/CPU"
  inference_host_address: "@cloud"

Load from YAML:

import degirum_vehicle

# Load from file
config, settings = degirum_vehicle.LicensePlateRecognizerConfig.from_yaml(
    yaml_file="lpr_config.yaml"
)

# Or from string
config, settings = degirum_vehicle.LicensePlateRecognizerConfig.from_yaml(
    yaml_str=yaml_content
)

# Create recognizer
lpr = degirum_vehicle.LicensePlateRecognizer(config)

When to use: Production environments, CI/CD pipelines, or when you need to version-control and share configurations across teams.

Example YAML: See lpr_recognition.yaml for a complete configuration.

---

Configuration Examples

Basic - Default Configuration

import degirum_vehicle

# Uses defaults: TFLITE/CPU running on cloud
lpr = degirum_vehicle.LicensePlateRecognizer()

Equivalent to:

config = degirum_vehicle.LicensePlateRecognizerConfig()
lpr = degirum_vehicle.LicensePlateRecognizer(config)

Defaults:

• Hardware: TFLITE/CPU

• Inference: @cloud

Cloud Experimentation

Try different hardware without local setup:

import degirum_vehicle

# Test Hailo-8 on cloud
config = degirum_vehicle.LicensePlateRecognizerConfig.from_hardware(
    "HAILORT/HAILO8",
    inference_host_address="@cloud"
)

lpr = degirum_vehicle.LicensePlateRecognizer(config)

Local Edge Deployment

Run on local Hailo-8 accelerator:

import degirum_vehicle

# Local Hailo-8
config = degirum_vehicle.LicensePlateRecognizerConfig.from_hardware(
    "HAILORT/HAILO8",
    inference_host_address="@local"
)

lpr = degirum_vehicle.LicensePlateRecognizer(config)

Remote Inference Server

Connect to dedicated AI server:

import degirum_vehicle

# Remote NVIDIA GPU server
config = degirum_vehicle.LicensePlateRecognizerConfig.from_hardware(
    "TENSORRT/GPU",
    inference_host_address="192.168.1.100:8778"
)

lpr = degirum_vehicle.LicensePlateRecognizer(config)

Mixed Hardware Setup

Use different hardware for detection and OCR:

import degirum_vehicle

# Detection on Hailo-8, OCR on GPU
detection_spec = degirum_vehicle.get_license_plate_detection_model_spec(
    device_type="HAILORT/HAILO8",
    inference_host_address="@local"
)

ocr_spec = degirum_vehicle.get_license_plate_ocr_model_spec(
    device_type="TENSORRT/GPU",
    inference_host_address="localhost"
)

config = degirum_vehicle.LicensePlateRecognizerConfig(
    license_plate_detection_model_spec=detection_spec,
    license_plate_ocr_model_spec=ocr_spec
)

lpr = degirum_vehicle.LicensePlateRecognizer(config)