# VideoDetect - Video Classification System

A production-grade video classification system for processing large-scale video corpora (~30TB) to classify videos based on demographic presence using deep learning models.

## Architecture

```
┌─────────────┐     ┌──────────────┐     ┌─────────────┐
│  Scanner    │────▶│  Processor   │────▶│  Results    │
│  (STORY-02) │     │  (STORY-03/04)│     │  (STORY-05) │
└─────────────┘     └──────────────┘     └─────────────┘
       │                    │                    │
       ▼                    ▼                    ▼
┌─────────────┐     ┌──────────────┐     ┌─────────────┐
│  MariaDB    │◀───▶│  GPU (P40)   │◀───▶│  Export     │
│  (Metadata) │     │  (Inference) │     │  (Parquet)  │
└─────────────┘     └──────────────┘     └─────────────┘
       │
       ▼
┌─────────────┐     ┌──────────────┐
│  Review UI  │◀───▶│ Active Learn │
│  (STORY-06) │     │  (STORY-07)  │
└─────────────┘     └──────────────┘
       │
       ▼
┌─────────────┐
│ Monitoring  │
│ (STORY-08)  │
└─────────────┘
```

## Quick Start

### Prerequisites
- Docker & Docker Compose v2+
- NVIDIA Container Toolkit
- 2× Tesla P40 GPUs (or compatible)
- NAS/SMB mount at `/mnt/nas` (configurable via env vars)

### Environment Variables

```bash
# Database
export DB_ROOT_PASSWORD=your_root_password
export DB_PASSWORD=your_db_password

# Paths (optional, defaults shown)
export NAS_INPUT_PATH=/mnt/nas/input
export NAS_OUTPUT_PATH=/mnt/nas/output
export MODELS_PATH=/mnt/nas/models
export TRAINING_PATH=/mnt/nas/training

# Grafana admin password
export GRAFANA_PASSWORD=your_grafana_password
```

### Start the Stack

```bash
docker-compose up -d
```

### Verify Services

```bash
# Check all containers are running
docker-compose ps

# Check GPU visibility in worker
docker exec videodetect-worker nvidia-smi

# Check database connectivity
docker exec videodetect-mariadb mysql -u videodetect -p videodetect -e "SHOW TABLES;"

# Access UI
open http://localhost:5000

# Access Grafana
open http://localhost:3000  (admin / your_grafana_password)

# Access Prometheus
open http://localhost:9090
```

## System Operation

### How Processes Start

**Service Initialization:**

1. **MariaDB** starts first with health check
2. **Worker** initializes via `src/main.py`:
   - Loads `config.yaml`
   - Sets up JSON logging with rotation
   - Connects to MariaDB (connection pooling)
   - Initializes database schema
   - Verifies GPU availability (CUDA/PyTorch)
   - Starts the `DirectoryScanner` in a background thread (scans permanent storage in place)
   - Creates `WorkerPool` with 1 worker thread
   - Enters job processing loop
3. **UI** starts Flask review interface via Gunicorn (2 workers)
4. **Monitoring** starts Prometheus and Grafana independently

### Processing Pipeline

The worker follows this flow for each video:

```
Pending → Lock → Probe → Sample → Detect → Classify → Aggregate → Route → Persist → Export → Cleanup → Completed
```

**Detailed Steps:**

1. **Job Queue** - Atomically lock `PENDING` jobs via `UPDATE status = 'PROCESSING'`
   - Priority: newest files first (`last_scan_time DESC`)
   - Max concurrent: 1 per GPU

2. **Probe Video** - Extract metadata via FFprobe
   - Duration, codec, resolution
   - Validate against codec whitelist (H.264, H.265, VP8/9, AV1)
   - Mark `UNSCANNABLE` if invalid

3. **Sample Frames** - Extract frames at configured interval (default: 30s)
   - Save as JPEG to `/scratch/{video_id}/frames/`
   - Quality: 2 (lower=better)

4. **Detect Faces** - YOLOv8n TensorRT inference (FP32)
   - Batch size auto-tuned by GPU memory monitor
   - NMS filtering (IoU: 0.45, confidence: 0.25)
   - Cap: 10 faces/frame, 100 faces/video

5. **Extract Crops** - Resize detected faces to 224×224
   - Save to `/scratch/{video_id}/crops/`

6. **Classify Crops** - MobileNetV3-Small TensorRT inference
   - Temperature-scaled softmax (T=1.0)
   - Returns confidence per crop

7. **Aggregate Confidence** - Combine crop confidences into video-level score
   - Strategy: `max` (most conservative)
   - Alternatives: `weighted_mean`, `top_k_mean`

8. **Route Decision** - Threshold-based routing:
   - `C ≥ 0.75` → **MATCH**
   - `0.45 ≤ C < 0.75` → **REVIEW** (human annotation)
   - `C < 0.45` → **SKIP**
   - No faces → **SKIP**

9. **Persist Results** - Atomic transaction:
   - Update `videos` table (confidence, routing, status)
   - Insert `processing_logs` row (audit trail)
   - State guard: only update if `status='PROCESSING'`

10. **Export** - Buffer and batch export (default: 100 videos)
    - Format: Parquet with Snappy compression
    - Path: `/data/output/{model_version}/`
    - Fallback: JSONL if Parquet fails

11. **Cleanup** - Delete `/scratch/{video_id}/` directory
    - Only after successful persistence
    - Prevents orphaned scratch files

**Directory Scanner Service (runs alongside the worker):**
- Scans the permanent storage location **in place** (no staging/copy step)
- Walks `/data/input` every **2 hours** by default (configurable via `scanner.scan_interval_seconds`)
- Detects new, modified, and removed video files by comparing against the DB
- Filters to video files by extension
- Computes SHA256 hash, probes metadata, validates codec
- Queues any video that has not been scanned yet as `PENDING` for the worker pool
- **Single-instance guard:** an in-process lock plus a DB lock (with a lease) ensure only one scan runs at a time — a long-running scan never overlaps another, even across multiple worker replicas. The lock lease is refreshed via heartbeats during the scan and is taken over automatically if a scanner crashes.

### Configuration Reference

All configuration is in `config.yaml`. Environment variable override format: `VD_<SECTION>_<KEY>` (e.g., `VD_SAMPLING_INTERVAL_SECONDS=60`).

#### Key Configuration Sections

**Sampling & Thresholds:**
```yaml
sampling:
  interval_seconds: 30          # Frame extraction frequency
  quality: 2                    # JPEG quality (1-31, lower=better)
  format: jpeg

thresholds:
  T_high: 0.75                  # MATCH threshold
  T_low: 0.45                   # REVIEW threshold
```

**GPU & Batching:**
```yaml
gpu:
  max_memory_gb: 18             # Target VRAM usage
  batch_size: auto              # Auto-tune based on available VRAM

batching:
  max_batch_size: 16            # Maximum batch size
  vram_target_gb: 16            # Target VRAM for batch tuning
  vram_reduce_threshold_gb: 16  # Reduce batch if above
  vram_increase_threshold_gb: 10 # Increase batch if below
```

**Storage Paths:**
```yaml
storage:
  scratch_path: /scratch        # Temporary processing (tmpfs)
  input_path: /data/input       # Source videos (NFS)
  output_path: /data/output     # Results (local/NAS)
  models_path: /models          # TensorRT models
  training_path: /data/training # Training data
```

**Database:**
```yaml
database:
  host: mariadb
  port: 3306
  name: videodetect
  user: videodetect
  password: videodetect123
  pool_size: 20                 # Connection pool size
  pool_min: 5
  pool_recycle: 3600            # Recycle connections after 1h
```

**Face Detection:**
```yaml
face_detection:
  model: yolo8n
  model_path: /models/face_detector/face_detector.trt
  input_size: 640
  confidence_threshold: 0.25
  iou_threshold: 0.45
  max_faces_per_frame: 10
  max_faces_per_video: 100
```

**Classification & Aggregation:**
```yaml
classifier:
  model: mobilenetv3-small
  model_path: /models/classifier/classifier.trt
  input_size: 224
  temperature: 1.0              # Calibration temperature

aggregation:
  strategy: max                 # max, weighted_mean, top_k_mean
  alpha: 1.0                    # weighted_mean weight for mean
  beta: 0.1                     # weighted_mean weight for variance
  top_k: 3                      # top_k_mean: average top 3 scores
```

**Export:**
```yaml
export:
  format: parquet               # parquet, jsonl, or both
  compression: snappy
  batch_size: 100               # Export after N videos
  include_frame_confidences: true
```

**Review UI:**
```yaml
review_ui:
  host: "0.0.0.0"
  port: 5000
  per_page: 20                  # Pagination
  top_k_frames: 5               # Show top-k contributing frames
  auth_enabled: false           # No auth per TC-06
  ssl_enabled: false            # Internal LAN only
```

#### Volume Mounts

From `docker-compose.yml`:

- **Input**: NFS mount → `/data/input` (read-only)
- **Output**: `./output` → `/data/output`
- **Models**: `./models` → `/models`
- **Training**: `./training` → `/data/training`
- **Scratch**: 100GB tmpfs at `/scratch` (RAM disk)

### Key Design Principles

- **Atomic state transitions** - Database locks prevent race conditions
- **Crash recovery** - `PROCESSING` jobs automatically requeued on restart
- **Idempotent** - Re-running same video produces same result
- **Stateless** - Scratch cleanup after each job
- **Fail-safe** - 3 retry attempts before marking `ERROR`
- **No auth/SSL** - Internal LAN deployment per TC-06

## Project Structure

```
VideoDetect/
├── docker-compose.yml          # Multi-service orchestration
├── config.yaml                 # All configuration
├── db/
│   └── schema.sql              # MariaDB schema
├── worker/
│   ├── Dockerfile              # Worker container image
│   └── requirements.txt        # Python dependencies
├── ui/
│   ├── Dockerfile              # UI container image
│   └── review/                 # Review UI templates
├── src/
│   ├── main.py                 # Worker entry point
│   ├── db_connector.py         # Database connection layer
│   ├── config_loader.py        # Configuration management
│   ├── logging_config.py       # Logging setup
│   ├── scanner.py              # Directory scanner (STORY-02)
│   ├── prober.py               # Video probing (STORY-02)
│   ├── frame_sampler.py        # Frame extraction (STORY-03)
│   ├── face_detector.py        # Face detection (STORY-04)
│   ├── classifier.py           # Classification (STORY-05)
│   ├── aggregator.py           # Confidence aggregation (STORY-05)
│   ├── router.py               # Threshold routing (STORY-05)
│   ├── result_updater.py       # Result persistence (STORY-06)
│   ├── data_export.py          # Parquet/JSONL export (STORY-06)
│   ├── review_api.py           # Review API (STORY-07)
│   ├── active_learning/        # Active learning pipeline (STORY-08)
│   │   ├── label_ingestor.py
│   │   ├── trainer.py
│   │   ├── validator.py
│   │   └── registry.py
│   ├── metrics.py              # Prometheus metrics (STORY-09)
│   ├── crash_recovery.py       # Crash recovery (STORY-09)
│   └── drift_detector.py       # Drift detection (STORY-09)
├── monitoring/
│   ├── prometheus/
│   │   └── prometheus.yml      # Prometheus config
│   └── grafana/
│       ├── dashboards/         # Grafana dashboard JSONs
│       └── provisioning/       # Grafana data source config
├── STORY-01.md through STORY-09.md  # Implementation stories
├── Plan.md                     # Implementation plan
└── Requirements.md             # Requirements document
```

## Implementation Stories

| Story | Description | Sprint | Points |
|-------|-------------|--------|--------|
| STORY-01 | Foundation & Infrastructure | 1-2 | 13 |
| STORY-02 | Core Ingestion & Codec Handling | 3-4 | 21 |
| STORY-03 | Frame Sampling | 5 | 13 |
| STORY-04 | Face Detection | 5-6 | 21 |
| STORY-05 | Classification & Confidence | 5-6 | 21 |
| STORY-06 | Results Persistence & Export | 5-6 | 13 |
| STORY-07 | Review Interface | 7 | 21 |
| STORY-08 | Active Learning Pipeline | 7-8 | 34 |
| STORY-09 | Observability & Hardening | 9+ | 34 |

## Hardware Requirements

- **GPUs:** 2× Tesla P40 24GB (compute capability 5.2)
- **CUDA:** ≤ 11.8
- **PyTorch:** ≤ 2.1.0
- **Inference:** FP32 only (no Tensor Cores)
- **Storage:** NVMe/SSD for scratch, NAS/SMB for input/output
- **RAM:** ≥ 32GB system RAM

## Key Design Decisions

1. **TensorRT FP32 only** — Tesla P40 has no Tensor Cores; FP16 would not provide benefit
2. **YOLOv8n + MobileNetV3** — Lightweight models optimized for throughput over accuracy
3. **Max aggregation** — Most conservative confidence strategy; use highest frame confidence
4. **Temperature scaling** — Calibrates confidence scores without retraining
5. **Head-only fine-tuning** — Faster retraining with frozen backbone
6. **Parquet export** — Efficient columnar format for analytics
7. **No auth/SSL** — Per TC-06, internal LAN only

## License

Proprietary — VideoDetect Project