spectrs

Fast spectrogram creation library.

What It Does
Installation
Quick Start
Features
Examples
Colormaps
Librosa Compatibility
Performance
API Reference

What It Does

spectrs is a Rust library for creating spectrograms from audio files. It provides:

STFT (Short-Time Fourier Transform) spectrograms with power or magnitude scaling
Mel-scaled spectrograms using HTK or Slaney scales
Audio I/O for reading WAV files (mono/stereo, 8/16/32-bit)
Resampling to arbitrary sample rates
Image export of spectrograms with multiple colormaps (Viridis, Magma, Inferno, Plasma, Gray)
Compatibility with librosa

Installation

Add spectrs to your project with

cargo add spectrs

or with image export support

cargo add spectrs --features image

Examples

Basic STFT Spectrogram

use spectrs::io::audio::read_audio_file_mono;
use spectrs::spectrogram::stft::{par_compute_spectrogram, SpectrogramType};

let (audio, _sr) = read_audio_file_mono("speech.wav")?;

// Compute magnitude spectrogram
let spec = par_compute_spectrogram(
    &audio,
    2048,   // n_fft: higher = better frequency resolution
    512,    // hop_length: lower = better time resolution
    2048,   // win_length: window size
    true,   // center: pad the signal
    SpectrogramType::Magnitude
);

Mel Spectrogram

use spectrs::spectrogram::mel::{convert_to_mel, MelScale};

// First compute STFT, then convert to mel
let mel_spec = convert_to_mel(
    &spec,
    22050,              // sample_rate
    2048,               // n_fft
    128,                // n_mels: number of mel bands
    Some(20.0),         // f_min: lowest frequency
    Some(8000.0),       // f_max: highest frequency
    MelScale::Slaney    // librosa default
);

Save Spectrogram as Image

use spectrs::io::image::{save_spectrogram_image, Colormap};

// Requires "image" feature
// Use default Viridis colormap (librosa/matplotlib default)
save_spectrogram_image(&mel_spec, "spectrogram.png", Colormap::Viridis)?;

// Or use other colormaps:
// save_spectrogram_image(&mel_spec, "spectrogram.png", Colormap::Magma)?;
// save_spectrogram_image(&mel_spec, "spectrogram.png", Colormap::Inferno)?;
// save_spectrogram_image(&mel_spec, "spectrogram.png", Colormap::Plasma)?;
// save_spectrogram_image(&mel_spec, "spectrogram.png", Colormap::Gray)?;

Single-Threaded Mode

For small files or embedded systems:

use spectrs::spectrogram::stft::compute_spectrogram;

// Non-parallelized version (lower overhead)
let spec = compute_spectrogram(
    &audio,
    512,
    160,
    400,
    false,
    SpectrogramType::Power
);

Complete Pipeline

use spectrs::io::audio::{read_audio_file_mono, resample};
use spectrs::spectrogram::stft::{par_compute_spectrogram, SpectrogramType};
use spectrs::spectrogram::mel::{convert_to_mel, MelScale};

// Read and process audio file
let (audio, sr) = read_audio_file_mono("song.wav")?;

// Resample to standard rate
let audio = resample(audio, sr, 22050)?;

// Compute spectrogram
let spec = par_compute_spectrogram(&audio, 2048, 512, 2048, true, SpectrogramType::Power);

// Convert to mel
let mel = convert_to_mel(&spec, 22050, 2048, 128, None, None, MelScale::HTK);

// Save as image (requires "image" feature)
#[cfg(feature = "image")]
{
    use spectrs::io::image::Colormap;
    spectrs::io::image::save_spectrogram_image(&mel, "output.png", Colormap::Viridis)?;
}

Colormaps

spectrs supports multiple colormaps for spectrogram visualization, including viridis, magma, inferno, plasma and simply gray. All colormaps implementations are based on the matplotlib colormaps.

Librosa Compatibility

spectrs is designed to replicate librosa's behaviour in the Rust ecosystem. Compatibility tests are part of the test suite, ensuring correlation between librosa's and spectrs' above 99% and relative error on relevant bands < 2%.

Run compatibility tests:

cargo test --test test_librosa_compatibility

spectrs 0.1.3