Configuration

Configuration Inheritance

LicensePlateTrackerConfig extends LicensePlateRecognizerConfig and inherits all base settings:

• Model specifications - License plate detection and OCR models (device_type, inference_host_address)

• OCR score threshold - Minimum confidence to display plate text (0.0-1.0)

• Show OCR score - Whether to display OCR confidence percentage

See LicensePlateRecognizer Configuration for details on these settings.

Configuration Parameters

LicensePlateTracker adds the following tracking-specific parameters:

Video Source

Parameters:

• video_source - Input video source (default: 0 for first webcam):

  • Integer (e.g., 0, 1) - Local webcam index

  • String path (e.g., "highway.mp4") - Video file

  • RTSP URL (e.g., "rtsp://192.168.1.100/stream") - IP camera

• video_source_fps_override (optional) - Override frame rate when camera reports incorrect FPS (default: 0.0 = no override)

• video_source_resolution_override (optional) - Override resolution as (width, height) tuple when camera reports incorrect dimensions (default: (0, 0) = no override)

Credence Count

Controls when a detected license plate is confirmed as a valid track for processing.

Parameter:

• credence_count - Number of consecutive frames a plate must appear before being confirmed (default: 4). Reduces false positives from momentary detections or camera noise.

Recommended values:

• 2-4 - Real-time monitoring (quick confirmation)

• 5-10 - High-traffic areas (reduce false positives)

• 10+ - Critical applications (maximum stability)

Alert Mode and Notifications

Controls when alerts are triggered and how notifications are delivered.

Parameters:

• alert_mode - When to trigger alerts (default: AlertMode.NONE):

  • AlertMode.NONE - No alerts

  • AlertMode.ON_UNKNOWNS - Alert when unknown plate detected

  • AlertMode.ON_KNOWNS - Alert when known plate detected

  • AlertMode.ON_ALL - Alert for all plates

• alert_once (bool) - Alert once per track (True) or every time plate text changes for the given track ID (False) (default: True)

• clip_duration (int) - Length of video clips in frames (default: 100, e.g., 100 frames ≈ 3.3 seconds at 30 FPS)

• notification_config (str) - Apprise configuration string for notification delivery

• notification_message (str) - Message template with variables: ${time}, ${plate_alerts}, ${filename}, ${url}

• notification_timeout_s (float, optional) - Timeout in seconds for sending notifications

Apprise notification examples:

• Email: "mailto://user:[email protected]"

• Slack: "slack://token/channel"

• Discord: "discord://webhook_id/webhook_token"

• SMS (Twilio): "twilio://account_sid:auth_token@from_phone/to_phone"

• Console: "console://" (testing)

See Apprise documentation for all supported services.

Clip Storage

Configuration for saving video clips to S3-compatible storage or local filesystem.

See Object Storage Configuration Reference for complete documentation including:

• Parameters (endpoint, bucket, access_key, etc.)

• Storage backend examples (AWS S3, MinIO, local filesystem)

• Environment-specific configurations

• Best practices

Alerting and Storage Combinations

Important: Both notifications and clip recording only trigger when alerts are generated. If alert_mode=AlertMode.NONE, no alerts are generated, so notifications and clip recording will not happen even if configured.

alert_mode	clip_duration	notification_config	Result
NONE	any	any	No alerts, no clips, no notifications
ON_ALL	> 0	configured	Alert + clip + notification for all plates
ON_UNKNOWNS	0	configured	Alert + notification only (no clips)

Live Streaming

Controls video output display.

Parameters:

• live_stream_mode - Output mode:

  • "LOCAL" - Display in local window

  • "WEB" - Stream via RTSP for web viewing

  • "NONE" - No live display

• live_stream_rtsp_url (str, optional) - RTSP URL path suffix (used when mode is "WEB")

Zone Filtering

Controls zone-based filtering for license plates.

Parameters:

• enable_zone_filter (bool) - Enable zone-based filtering (default: False)

• zone (list) - Zone polygon as list of [x, y] coordinate pairs. Minimum 3 points required. Example: [[100, 200], [500, 200], [500, 600], [100, 600]]

Configuration Options

Option 1: Python Configuration

Option 1: Python Configuration

import degirum_vehicle
import degirum_tools

config = degirum_vehicle.LicensePlateTrackerConfig(
    # Models (using model registry)
    license_plate_detection_model_spec=degirum_vehicle.get_license_plate_detection_model_spec(
        device_type="HAILORT/HAILO8",
        inference_host_address="@cloud"
    ),
    license_plate_ocr_model_spec=degirum_vehicle.get_license_plate_ocr_model_spec(
        device_type="HAILORT/HAILO8",
        inference_host_address="@cloud"
    ),
    
    # OCR settings
    show_ocr_score=True,
    ocr_score_threshold=0.6,
    
    # Video source
    video_source="rtsp://192.168.1.100/stream",
    
    # Tracking
    credence_count=4,
    
    # Alerting
    alert_mode=degirum_vehicle.AlertMode.ON_ALL,
    alert_once=True,
    clip_duration=100,
    
    # Clip storage
    clip_storage_config=degirum_tools.ObjectStorageConfig(
        endpoint="./lpr_clips",
        bucket="plates"
    ),
    
    # Notifications
    notification_config="mailto://[email protected]",
    notification_message="🚗 ${time}: Plate detected: ${plate_alerts}",
    notification_timeout_s=10.0,
    
    # Live display
    live_stream_mode="WEB",
    live_stream_rtsp_url="lpr_feed",
)

tracker = degirum_vehicle.LicensePlateTracker(config)

Option 2: YAML Configuration

LicensePlateTrackerConfig can be initialized from a YAML file or string using the from_yaml() method. This approach separates configuration from code, making it easier to version control settings, share configurations across teams, and maintain different configs for development, staging, and production environments.

Complete YAML structure:

# License plate detection model
license_plate_detection_model:
  hardware: HAILORT/HAILO8
  inference_host_address: "@cloud"
  
# License plate OCR model
license_plate_ocr_model:
  hardware: HAILORT/HAILO8
  inference_host_address: "@cloud"

# OCR settings
show_ocr_score: true
ocr_score_threshold: 0.6

# Video source
video_source: "rtsp://192.168.1.100/stream"
video_source_fps_override: 0.0              # 0 = use source FPS (no override)
video_source_resolution_override: [0, 0]    # [0, 0] = use source resolution (no override)

# Tracking
credence_count: 4

# Alerting
alerts:
  alert_mode: ON_ALL                        # NONE, ON_UNKNOWNS, ON_KNOWNS, ON_ALL
  alert_once: true
  clip_duration: 100
  notification_config: "mailto://[email protected]"
  notification_message: "🚗 ${time}: Plate detected: ${plate_alerts}"
  notification_timeout_s: 10.0

# Clip storage
storage:
  endpoint: "./lpr_clips"
  access_key: ""
  secret_key: ""
  bucket: "plates"
  url_expiration_s: 3600

# Zone filtering
enable_zone_filter: false
zone: []

# Live streaming
live_stream:
  mode: WEB                                 # LOCAL, WEB, NONE
  rtsp_url: "lpr_feed"

Loading from YAML

import degirum_vehicle

config, _ = degirum_vehicle.LicensePlateTrackerConfig.from_yaml(yaml_file="lpr_tracking.yaml")
tracker = degirum_vehicle.LicensePlateTracker(config)

Returns:

• config - Initialized LicensePlateTrackerConfig object

• settings - Raw dictionary (useful for debugging)

Loading from YAML String

import degirum_vehicle

yaml_string = """
license_plate_detection_model:
  hardware: HAILORT/HAILO8
  inference_host_address: "@cloud"
license_plate_ocr_model:
  hardware: HAILORT/HAILO8
  inference_host_address: "@cloud"
video_source: 0
alerts:
  alert_mode: ON_ALL
"""

config, _ = degirum_vehicle.LicensePlateTrackerConfig.from_yaml(yaml_str=yaml_string)
tracker = degirum_vehicle.LicensePlateTracker(config)

Benefits of YAML

• Clean separation - Config separate from code

• Easy modification - Change hardware without editing code

• Version control - Track config changes in git

• Team collaboration - Share standardized configs

• Multiple environments - dev.yaml, staging.yaml, prod.yaml

Configuration Examples

Example 1: Parking Lot Monitoring

Monitor RTSP camera, alert on all plates, save clips, send email:

import degirum_vehicle
import degirum_tools

config = degirum_vehicle.LicensePlateTrackerConfig(
    license_plate_detection_model_spec=degirum_vehicle.get_license_plate_detection_model_spec(
        device_type="HAILORT/HAILO8",
        inference_host_address="@cloud"
    ),
    license_plate_ocr_model_spec=degirum_vehicle.get_license_plate_ocr_model_spec(
        device_type="HAILORT/HAILO8",
        inference_host_address="@cloud"
    ),
    video_source="rtsp://192.168.1.100/stream",
    credence_count=4,
    alert_mode=degirum_vehicle.AlertMode.ON_ALL,
    alert_once=True,
    clip_duration=150,
    clip_storage_config=degirum_tools.ObjectStorageConfig(
        endpoint="./parking_clips",
        bucket="all_plates"
    ),
    notification_config="mailto://[email protected]",
    notification_message="⚠️ Plate detected at ${time}: ${plate_alerts}",
    live_stream_mode="WEB",
    live_stream_rtsp_url="parking_feed",
)

tracker = degirum_vehicle.LicensePlateTracker(config)

Example 2: Local Video File Processing

Process local video file, display locally:

config = degirum_vehicle.LicensePlateTrackerConfig(
    license_plate_detection_model_spec=degirum_vehicle.get_license_plate_detection_model_spec(
        device_type="TFLITE/CPU",
        inference_host_address="@cloud"
    ),
    license_plate_ocr_model_spec=degirum_vehicle.get_license_plate_ocr_model_spec(
        device_type="TFLITE/CPU",
        inference_host_address="@cloud"
    ),
    video_source="highway_traffic.mp4",
    alert_mode=degirum_vehicle.AlertMode.NONE,
    live_stream_mode="LOCAL",
    show_ocr_score=True,
)

tracker = degirum_vehicle.LicensePlateTracker(config)

Example 3: High-Traffic Zone Filtering

Reduce false positives with zone filtering and higher credence:

config = degirum_vehicle.LicensePlateTrackerConfig(
    license_plate_detection_model_spec=degirum_vehicle.get_license_plate_detection_model_spec(
        device_type="HAILORT/HAILO8",
        inference_host_address="@cloud"
    ),
    license_plate_ocr_model_spec=degirum_vehicle.get_license_plate_ocr_model_spec(
        device_type="HAILORT/HAILO8",
        inference_host_address="@cloud"
    ),
    video_source="rtsp://toll-camera/stream",
    credence_count=8,  # Higher confirmation threshold
    alert_mode=degirum_vehicle.AlertMode.ON_ALL,
    enable_zone_filter=True,
    zone=[[100, 200], [800, 200], [800, 600], [100, 600]],  # Define detection zone
    live_stream_mode="LOCAL",
)

tracker = degirum_vehicle.LicensePlateTracker(config)