stemdeckapp/stemdeck

First public alpha of StemDeck. Local, single-user audio stem
separation with a DAW-style mixer.

Highlights

• 6-stem separation via Demucs htdemucs_6s. Auto-selects CUDA →
  MPS → CPU; ~3-5× speedup on Apple Silicon over CPU.
• DAW-style waveform editor with min/max rendering, zoom, loop
  region drag, gold playhead, and stem-aligned lanes.
• Per-stem mixer: volume fader, mute, solo, monitor (solo-only),
  with state synced between mixer and stems sidebar.
• Stem subset extraction: pick which stems to keep on import. The
  studio surfaces a 7th "Original" lane (full song minus selection)
  for A/B reference, plus a downloadable summed mix.wav.
• Live VU per stem: post-gain RMS via Web Audio with peak hold +
  slow falloff.
• Song analysis in the now-playing card: BPM (librosa beat
  tracker), key + scale + confidence (Albrecht-Shanahan), integrated
  LUFS (BS.1770 via pyloudnorm), sample peak in dBFS.
• Cancellable jobs at any pipeline stage (download, Demucs,
  ffmpeg amix). Active subprocess is terminated and the partial job
  dir is cleaned up.

Setup

• macOS / Linux: git clone … && ./run.sh setup && ./run.sh start.
  The setup subcommand installs ffmpeg + uv via Homebrew or apt and
  runs uv sync.
• Docker: docker compose -f build/docker-compose.yml up --build.
  No GPU on macOS Docker; Apple Silicon users should prefer the
  native install.

CI / quality

• Woodpecker pipeline runs lint (ruff), unit tests (pytest), Python
  SAST (bandit), dependency CVE audit (pip-audit), and filesystem
  security scan (trivy fs + trivy config). No build/publish.
• Container hardening: non-root app user in the runtime image.

Known limitations

• Local-only / single-user. Not designed for multi-tenant hosting.
• Single concurrent pipeline (asyncio.Semaphore(1)). Multiple jobs
  queue rather than running in parallel.
• yt-dlp YouTube downloads are subject to YouTube ToS. See the
  Disclaimer in the README; usage is your responsibility.
• Browser memory grows on long videos because each stem is decoded
  into a Web Audio buffer for the overview waveform.

Thanks

Demucs (htdemucs_6s), wavesurfer.js, ffmpeg, yt-dlp, librosa,
pyloudnorm — this project is glue around their work.