Quick Start

Basic usage

Every function in pyminidsp accepts and returns NumPy float64 arrays. Input arrays are automatically converted if needed.

import pyminidsp as md

# Generate a 440 Hz sine wave (1 second at 44.1 kHz)
signal = md.sine_wave(44100, amplitude=1.0, freq=440.0, sample_rate=44100.0)

# Check the signal's RMS level (unit sine ≈ 0.707)
print(md.rms(signal))

# Always call shutdown() when done to free internal FFT caches
md.shutdown()

Note

shutdown() is registered with atexit, so it runs automatically at interpreter exit. You can also call it explicitly to free memory sooner.

Signal generation

pyminidsp provides a range of test signal generators:

# Gaussian white noise (reproducible via seed)
noise = md.white_noise(4096, amplitude=1.0, seed=42)

# Linear chirp from 200 Hz to 4 kHz
chirp = md.chirp_linear(16000, f_start=200.0, f_end=4000.0, sample_rate=16000.0)

# Shepard tone (endlessly rising pitch illusion)
shepard = md.shepard_tone(44100, amplitude=0.8, base_freq=440.0,
                           sample_rate=44100.0, rate_octaves_per_sec=0.5)

Spectral analysis

# Magnitude spectrum (N/2 + 1 bins, from DC to Nyquist)
mag = md.magnitude_spectrum(signal)

# Short-Time Fourier Transform
spec = md.stft(signal, n=512, hop=128)
# spec.shape == (num_frames, 257)

# Mel-frequency cepstral coefficients (single frame)
coeffs = md.mfcc(signal[:512], sample_rate=44100.0, num_mels=26, num_coeffs=13)

Filtering

# Biquad IIR filter (low-pass at 1 kHz)
lpf = md.BiquadFilter(md.LPF, freq=1000.0, sample_rate=44100.0)
filtered = lpf.process_array(signal)

# FIR filter with custom coefficients
import numpy as np
coeffs = np.array([0.25, 0.5, 0.25])
out = md.fir_filter(signal, coeffs)

# FFT overlap-add convolution (faster for long kernels)
out = md.convolution_fft_ola(signal, kernel)

DTMF encoding and decoding

# Generate a DTMF tone sequence
sig = md.dtmf_generate("5551234", sample_rate=8000.0)

# Detect tones in the signal
tones = md.dtmf_detect(sig, sample_rate=8000.0)
for digit, start_s, end_s in tones:
    print(f"{digit}  {start_s:.3f}–{end_s:.3f} s")

Delay estimation (GCC-PHAT)

import numpy as np

# Simulate a delayed copy
sig_a = md.sine_wave(1024, freq=440.0, sample_rate=44100.0)
sig_b = np.roll(sig_a, 5)   # 5-sample delay

delay, entropy = md.get_delay(sig_a, sig_b, margin=20, weighting=md.GCC_PHAT)
print(f"Estimated delay: {delay} samples")

Audio steganography

# Hide a secret message in audio
host = md.sine_wave(44100, amplitude=0.8, freq=440.0, sample_rate=44100.0)
stego, n_encoded = md.steg_encode(host, "secret message",
                                   sample_rate=44100.0, method=md.STEG_LSB)

# Recover the message
recovered = md.steg_decode(stego, sample_rate=44100.0, method=md.STEG_LSB)
print(recovered)  # "secret message"