# Module: start_inference

## Purpose
Entry point for running inference on video files using a TensorRT engine. Downloads the encrypted model from the API/CDN, initializes the engine, and processes video.

## Public Interface

| Function | Signature | Returns | Description |
|----------|-----------|---------|-------------|
| `get_engine_filename` | `(device_id=0) -> str \| None` | Engine filename | Generates GPU-specific engine filename (duplicate of TensorRTEngine.get_engine_filename) |

`__main__` block: Creates ApiClient, downloads encrypted TensorRT model (split big/small), initializes TensorRTEngine, runs Inference on a test video.

## Internal Logic
- **Model download flow**: ApiClient → `load_big_small_resource` → reassembles from local big part + API-downloaded small part → decrypts with model encryption key → raw engine bytes.
- **Inference setup**: TensorRTEngine initialized from decrypted bytes, Inference configured with confidence_threshold=0.5, iou_threshold=0.3.
- **Video source**: Hardcoded to `tests/ForAI_test.mp4`.
- **get_engine_filename()**: Duplicates `TensorRTEngine.get_engine_filename()` — generates `azaion.cc_{major}.{minor}_sm_{sm_count}.engine` based on CUDA device compute capability and SM count.

## Dependencies
- `constants` — config file paths
- `api_client` — ApiClient, ApiCredentials for model download
- `cdn_manager` — CDNManager, CDNCredentials (imported but CDN managed by api_client)
- `inference/inference` — Inference pipeline
- `inference/tensorrt_engine` — TensorRTEngine
- `security` — model encryption key
- `utils` — Dotdict
- `pycuda.driver` (external) — CUDA device queries
- `yaml` (external)

## Consumers
None (entry point).

## Data Models
None.

## Configuration
- Confidence threshold: 0.5
- IoU threshold: 0.3
- Video path: `tests/ForAI_test.mp4` (hardcoded)

## External Integrations
- Azaion API + CDN for model download
- TensorRT GPU inference
- OpenCV video capture and display

## Security
- Model is downloaded encrypted (split big/small) and decrypted locally
- Uses hardware-bound and model encryption keys

## Tests
None.