Image Acquisition Engine

The Image Acquisition Engine (Alert.CA.ImageAcquisition) is the primary application in the solution. It is an Azure Functions v4 app using Durable Functions with the Netherite backend to continuously capture images from hundreds of cameras in parallel through long-running orchestration loops.

Architecture Overview

Tech Stack

Component	Technology
Runtime	.NET 10, Azure Functions v4 (Isolated Worker)
Orchestration	Durable Functions with Netherite backend
Netherite Config	Max 2000 orchestrators, 4000 activities, 32 partitions
Hub Name	imgacqhub
Image Processing	Emgu.CV (OpenCV), System.Drawing
Camera Protocol	VAPIX via IVAPIXClient
Real-time	SignalR Client (auto-reconnect with exponential backoff)
Monitoring	Application Insights (custom telemetry)
Config	Azure App Configuration + Key Vault

Project Structure

Alert.CA.ImageAcquisition/
├── Program.cs                          # DI registration + middleware
├── host.json                           # Netherite + function host config
├── Functions/
│   ├── CameraOrchestratorFunction.cs   # Main entry point (Cosmos trigger)
│   ├── RefreshPTZForFE.cs              # Timer: sync PTZ to frontend entity
│   ├── VapixOrchestrations/
│   │   ├── VapixOrchestrator.cs        # Orchestration lifecycle manager
│   │   ├── BaseOrchestrationFunction.cs # Eternal loop (~350 lines)
│   │   ├── StandardModeFunctions.cs    # SINGLE + PANO capture
│   │   ├── TurboModeFunctions.cs       # High-speed wrapper
│   │   ├── LeaseModeFunctions.cs       # Manual control mode
│   │   ├── IntervalAcquisitionFunctions.cs # Time-interval base
│   │   └── IO/
│   │       ├── RequestImageFunctions.cs        # Single image activity
│   │       ├── RequestPanoImagesFunctions.cs    # Panoramic image activity
│   │       ├── CameraMovementFunctions.cs       # 7 PTZ activity functions
│   │       ├── CameraControlQueueFunctions.cs   # 6 HTTP endpoints for PTZ
│   │       └── SubmitCameraStatusFunctions.cs   # ESRI status reporting
│   ├── MobotixOrchestrations/
│   │   └── MobotixOrchestrator.cs      # Skeleton (future)
│   └── OrchestrationManagement/
│       ├── GetDurableEntityFunctions.cs     # Query entity state
│       ├── PurgeAllOrchestrations.cs        # Cleanup all
│       ├── PurgeSingleOrchestration.cs      # Cleanup one
│       ├── ResetAllOrchestrations.cs        # Reset all
│       └── ResetFailedOrchestrations.cs     # Reset failed
├── Services/
│   ├── BaseImageStorageService.cs       # Abstract base for image storage
│   ├── SingleImageStorageService.cs     # Single image + thumbnail
│   ├── PanoImageStorageService.cs       # Panoramic stitching + storage
│   ├── PreStitchedImageStorageService.cs # Pre-stitch ZIP archive
│   ├── SignalRConnectionService.cs      # Real-time broadcasting
│   └── DurableDataStoreService.cs       # Entity state → Table Storage
├── Middleware/
│   └── CorsMiddleware.cs               # Local dev CORS
└── Utilities/
    └── OrchestrationModeHelper.cs       # Mode state transitions

Key Concepts

• Eternal Orchestration — Each camera runs an infinite orchestration loop using ContinueAsNew(). The loop captures images, checks for commands, sleeps, and repeats forever until explicitly terminated.
• Durable Entities — Per-camera CameraState entities maintain mode, PTZ position, command queues, and timing data across orchestration restarts.
• Activity Functions — All I/O (camera communication, image storage, ESRI updates) is isolated in activity functions so failures don't crash the orchestration.
• Cosmos Change Feed Trigger — The engine reacts to device configuration changes in real-time, starting/stopping orchestrations automatically.

Documentation Sections

• Cosmos DB Change Feed Trigger — How the engine starts, stops, and redeploys orchestrations
• Orchestration Lifecycle — VapixOrchestrator lifecycle management and the eternal loop pattern
• Acquisition Modes — SINGLE, PANO, LEASED, and TURBO mode behavior
• Activity Functions — Image capture, camera movement, and status reporting
• Camera Control Queue — HTTP endpoints for real-time PTZ/focus/brightness commands
• SignalR Integration — Real-time image metadata broadcasting
• Orchestration Management — Admin endpoints for querying, purging, and resetting orchestrations
• Telemetry & Monitoring — Application Insights custom metrics