Separação de fontes

Open-Unmix HQ divide uma faixa musical estéreo em quatro stems independentes — vocais, bateria, baixo e outros. Quatro modelos BiLSTM independentes (um por stem) produzem máscaras de magnitude sobre a STFT da mistura; um pós-filtro Wiener opcional os reconcilia. Executa no Apple Silicon via MLX.

Dois motores estão disponíveis: Open-Unmix HQ (leve, o padrão) e HTDemucs (Demucs v4) — um modelo Hybrid Transformer de maior qualidade selecionado com --engine htdemucs. Ambos executam no Apple Silicon via MLX e produzem os mesmos quatro stems a 44.1 kHz.

Visão geral

Arquitetura

Four independent stems, each a copy of the same network:

StageShape / operation
STFT4096-point FFT, 1024-hop, periodic Hann window, reflect-pad. 2049 frequency bins per frame.
Input normalizeCrop to 1487 bins (≈16 kHz), apply learned per-bin mean + scale from training.
EncoderLinear 2974 → 512 + BatchNorm + tanh. Input is 2 channels × 1487 bins.
BiLSTM3 layers, 256 hidden per direction (512 effective). Captures temporal context across frames.
DecoderSkip-concat of encoder and LSTM outputs (1024) → Linear 1024 → 512 + BN + ReLU → Linear 512 → 4098.
Output denorm + maskElement-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

ComponentValue
Parameters / stem8.9M
Parameters total (4 stems)~35.6M
Sample rate44.1 kHz stereo
Chunk latencyOffline (full-track STFT)
Weightsaufklarer/OpenUnmix-HQ-MLX (safetensors, ~136 MB)
Upstreamsigsep/open-unmix-pytorch (Stöter et al., JOSS 2019)

HTDemucs (Demucs v4)

For higher separation quality — especially on bass and drums — the package also ships HTDemucs, Meta's Hybrid Transformer Demucs. It merges a spectrogram branch and a waveform branch through a cross-domain transformer; the shipped htdemucs_ft variant is a bag of four fine-tuned sub-models, one per stem. Weights download from HuggingFace on first use. On a directional MUSDB-sample benchmark (museval / BSSEval v4) it averages +3.01 dB SDR over UMX-HQ, with the biggest gains on bass (+5.75 dB).

ComponentValue
Parameters168M (4 × 42M fine-tuned sub-models)
Sample rate44.1 kHz stereo
Windowing7.8 s segments, 25% overlap, triangular cross-fade
Weightsaufklarer/HTDemucs-FT-MLX (fp16, ~320 MB)
Upstreamfacebookresearch/demucs (Rouard et al., ICASSP 2023)

Início 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/ (Open-Unmix)
speech separate song.wav --engine htdemucs            # Demucs v4 — higher quality
speech separate song.wav --engine htdemucs --htdemucs-precision int8  # smaller int8 bundle
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

Quando usar

Open-Unmix cabe quando…

…você precisa de uma etapa leve e offline de separação de fontes dentro de um app ou pipeline no Apple Silicon. 8,9 M parâmetros por stem mantêm download e memória modestos. Máscara de magnitude mais Wiener rende bons stems na maioria do pop/rock. Para isolamento vocal de ponta em material de estúdio, troque para o motor HTDemucs (Demucs v4) incluído via --engine htdemucs; o Open-Unmix continua sendo a ponta leve, pronta para embarcar no seu app, desse compromisso.