Separación de fuentes
Open-Unmix HQ divide una pista musical estéreo en cuatro stems independientes — voces, batería, bajo y otros. Cuatro modelos BiLSTM independientes (uno por stem) producen máscaras de magnitud sobre el STFT de la mezcla; un posfiltrado Wiener opcional los reconcilia. Se ejecuta en Apple Silicon mediante MLX.
Qué es
- 4 stems per track — vocals, drums, bass, other. Each is a 2-channel 44.1 kHz stem file.
- Magnitude-mask model — each stem model predicts a non-negative mask applied to the mixture spectrogram; phase is taken from the mixture.
- Wiener post-filter (optional) — soft-mask refinement across all 4 stems so they sum coherently back to the mixture. Adds ~0.5 dB SDR.
- Small footprint — 8.9M params per stem, ~136 MB total for all 4 stems.
- Apache-2.0 — upstream weights under MIT, our CoreML/MLX conversion under Apache-2.0.
Arquitectura
Four independent stems, each a copy of the same network:
| Stage | Shape / operation |
|---|---|
| STFT | 4096-point FFT, 1024-hop, periodic Hann window, reflect-pad. 2049 frequency bins per frame. |
| Input normalize | Crop to 1487 bins (≈16 kHz), apply learned per-bin mean + scale from training. |
| Encoder | Linear 2974 → 512 + BatchNorm + tanh. Input is 2 channels × 1487 bins. |
| BiLSTM | 3 layers, 256 hidden per direction (512 effective). Captures temporal context across frames. |
| Decoder | Skip-concat of encoder and LSTM outputs (1024) → Linear 1024 → 512 + BN + ReLU → Linear 512 → 4098. |
| Output denorm + mask | Element-wise multiply with mixture magnitude; phase from mixture; iSTFT overlap-add. |
| Wiener (optional) | Power-ratio masks across all 4 stem estimates. Refines phase so stems sum to mixture. |
Modelo
| Component | Value |
|---|---|
| Parameters / stem | 8.9M |
| Parameters total (4 stems) | ~35.6M |
| Sample rate | 44.1 kHz stereo |
| Chunk latency | Offline (full-track STFT) |
| Weights | aufklarer/OpenUnmix-HQ-MLX (safetensors, ~136 MB) |
| Upstream | sigsep/open-unmix-pytorch (Stöter et al., JOSS 2019) |
Inicio rápido — Swift
import SourceSeparation
import AudioCommon
let separator = try await SourceSeparator.fromPretrained()
let stereo = try AudioFileLoader.loadStereo(
url: URL(fileURLWithPath: "song.wav"),
targetSampleRate: 44100
)
let stems = separator.separate(audio: stereo, sampleRate: 44100)
// stems[.vocals], stems[.drums], stems[.bass], stems[.other]
// Each is [[Float]] — left channel, right channel.
try WAVWriter.writeStereo(
left: stems[.vocals]![0],
right: stems[.vocals]![1],
sampleRate: 44100,
to: URL(fileURLWithPath: "vocals.wav")
)
Pass wiener: true (default) for best quality. Pass targets: [.vocals] to extract only a subset of stems and skip the other models.
CLI
speech separate song.wav # all 4 stems into song_stems/
speech separate song.wav --stems vocals # vocals only
speech separate song.wav --stems vocals,drums # subset
speech separate song.wav --output-dir /tmp/stems/ # custom output dir
speech separate song.wav --verbose # show timing
Cuándo usarlo
…necesitas una pasada de separación de fuentes ligera y offline dentro de una app o pipeline en Apple Silicon. 8,9 M parámetros por stem mantienen descarga y memoria contenidas. Enmascaramiento de magnitud más Wiener rinde bien en la mayoría del pop/rock. Para aislamiento de voces de nivel estudio recurrirías a un modelo más grande tipo Demucs/MDX-Net; este paquete apunta al equilibrio práctico para llevar a una app.