# Step 1 — Demucs Setup

**Status: DONE**

## What we did

Installed Demucs and ran it on a local audio file to confirm the model works before building anything around it.

---

## What was installed

```bash
# CPU-only PyTorch (saves ~2GB vs CUDA build — no GPU on this machine)
pip install torch torchaudio --index-url https://download.pytorch.org/whl/cpu

# Demucs model
pip install demucs

# Required for saving output audio files
pip install torchcodec
```

## How to run it manually

```bash
source venv/bin/activate
demucs --two-stems=vocals -n mdx_extra "path/to/audio.mp3"
```

- `-n mdx_extra` — lighter model, faster on CPU
- `--two-stems=vocals` — splits into two files: voice and background

## Output

Results land in:
```
separated/mdx_extra/<track-name>/
├── vocals.wav       # isolated voice
└── no_vocals.wav    # background / everything else
```

---

## Notes

- Processing time: ~40 seconds for a 33-second clip on ThinkPad X270
- Fan noise mixed into voice is not fully removed — Demucs is a music separator, not a speech denoiser
- Future fix: swap Demucs for **DeepFilterNet** (better for speech + background noise)
- Model weights cached at `~/.cache/torch/hub/checkpoints/` — no re-download on next run