rubato-fft-node

High-performance native audio DSP for Node.js, powered by Rust.

Features

• Resampling — High-quality sample rate conversion via Rubato, with configurable quality presets (sinc/polynomial)
• FFT — Real FFT, inverse FFT, magnitude/power spectrum via RustFFT + realfft
• Window Functions — Hann, Hamming, Blackman, Blackman-Harris, Kaiser, Flat Top, Bartlett, Rectangular
• Biquad Filters — Lowpass, highpass, bandpass, notch, allpass, shelving, peaking EQ
• Level Metering — RMS and peak measurement in linear and dBFS
• Format Conversion — Int16/Float32 conversion, interleave/deinterleave

All compute-intensive operations return Promises executed on the libuv thread pool via NAPI-RS AsyncTask, keeping the Node.js event loop free.

Install

npm install rubato-fft-node

Prebuilt binaries are provided for:

• macOS ARM64 (Apple Silicon)
• macOS x64 (Intel)
• Linux x64 (glibc)
• Windows x64

No Rust toolchain required for installation.

Quick Start

Resampling

import { Resampler, ResamplerQuality, resample } from 'rubato-fft-node';

// One-shot
const output = await resample(audioData, 48000, 16000);

// Streaming (maintains filter state across calls)
const resampler = new Resampler(48000, 16000, 1, ResamplerQuality.High);
const chunk1 = await resampler.process(inputChunk1);
const chunk2 = await resampler.process(inputChunk2);
const remaining = await resampler.flush();
resampler.dispose();

FFT / Spectrum Analysis

import { SpectrumAnalyzer, realFft, realIfft, magnitudeSpectrum } from 'rubato-fft-node';

// Spectrum analyzer with windowing
const analyzer = new SpectrumAnalyzer(48000, 4096, 'blackmanHarris');
const result = await analyzer.analyze(audioData);
console.log(`Peak: ${result.peakFrequency}Hz at ${result.peakMagnitude}dB`);

// Raw FFT
const spectrum = await realFft(signal, 1024);
const recovered = await realIfft(spectrum, 1024);

// Magnitude spectrum
const mags = await magnitudeSpectrum(signal, 1024);

Window Functions

import { createWindow, applyWindow } from 'rubato-fft-node';

const coefficients = createWindow('blackmanHarris', 1024); // sync
const windowed = await applyWindow(signal, 'hann');        // async

Biquad Filters

import { designBiquad, BiquadFilter } from 'rubato-fft-node';

const coeffs = designBiquad('lowpass', 48000, 1000, 0.707);
const filter = new BiquadFilter(coeffs);
const filtered = await filter.process(audioData);
filter.reset();

Level Metering

import { measureLevel } from 'rubato-fft-node';

const level = await measureLevel(audioData);
console.log(`RMS: ${level.rmsDb} dBFS, Peak: ${level.peakDb} dBFS`);

Format Conversion

import { int16ToFloat32, float32ToInt16, interleave, deinterleave } from 'rubato-fft-node';

const floats = await int16ToFloat32(int16Data);
const ints = await float32ToInt16(floatData);

const stereo = await interleave([leftChannel, rightChannel]);
const [left, right] = await deinterleave(stereoData, 2);

API Reference

Resampler

| API | Type | Description | |-----|------|-------------| | new Resampler(inputRate, outputRate, channels?, quality?) | Constructor | Create streaming resampler | | resampler.process(input) | Promise<Float32Array> | Process audio chunk | | resampler.flush() | Promise<Float32Array> | Flush remaining samples | | resampler.reset() | void | Reset filter state | | resampler.outputDelay | number | Output delay in frames | | resampler.dispose() | void | Release native resources | | resample(input, inRate, outRate, ch?, quality?) | Promise<Float32Array> | One-shot resample |

Quality Presets

| Preset | Method | Description | |--------|--------|-------------| | Best | Sinc (len=256, cubic) | Highest quality, highest CPU | | High | Sinc (len=128, cubic) | Good balance (default) | | Medium | Sinc (len=64, linear) | Moderate quality | | Low | Polynomial cubic | Fast | | Fastest | Polynomial linear | Fastest, lowest quality |

FFT / Spectrum

| API | Type | Description | |-----|------|-------------| | new SpectrumAnalyzer(sampleRate, fftSize, window?, targetRate?) | Constructor | Create analyzer | | analyzer.analyze(audioData) | Promise<SpectrumResult> | Analyze audio | | magnitudeSpectrum(signal, fftSize) | Promise<Float32Array> | Magnitude spectrum | | powerSpectrumDb(signal, fftSize) | Promise<Float32Array> | Power spectrum (dB) | | realFft(signal, fftSize) | Promise<Float32Array> | Forward real FFT | | realIfft(spectrum, fftSize) | Promise<Float32Array> | Inverse real FFT |

Window / Filter / Level / Convert

| API | Type | Description | |-----|------|-------------| | createWindow(type, length) | Float64Array | Generate window coefficients (sync) | | applyWindow(signal, type) | Promise<Float32Array> | Apply window function | | designBiquad(type, rate, freq, q?, gain?) | BiquadCoefficients | Design filter (sync) | | new BiquadFilter(coefficients) | Constructor | Create stateful filter | | filter.process(input) | Promise<Float32Array> | Apply filter | | measureLevel(samples) | Promise<LevelResult> | Measure RMS/peak level | | int16ToFloat32(input) | Promise<Float32Array> | Convert Int16 → Float32 | | float32ToInt16(input) | Promise<Int16Array> | Convert Float32 → Int16 | | interleave(channels) | Promise<Float32Array> | Interleave channels | | deinterleave(data, numCh) | Promise<Float32Array[]> | Deinterleave channels |

Supported Platforms

| Platform | Architecture | Status | |----------|-------------|--------| | macOS | ARM64 (Apple Silicon) | ✅ | | macOS | x64 (Intel) | ✅ | | Linux | x64 (glibc) | ✅ | | Windows | x64 | ✅ |

License

MIT