Core IO and DSP

Audio processing

load(path[, sr, mono, offset, duration, …])	Load an audio file as a floating point time series.
to_mono(y)	Force an audio signal down to mono.
resample(y, orig_sr, target_sr[, res_type, …])	Resample a time series from orig_sr to target_sr
get_duration([y, sr, S, n_fft, hop_length, …])	Compute the duration (in seconds) of an audio time series, feature matrix, or filename.
autocorrelate(y[, max_size, axis])	Bounded auto-correlation
zero_crossings(y[, threshold, …])	Find the zero-crossings of a signal y: indices i such that sign(y[i]) != sign(y[j]).
clicks([times, frames, sr, hop_length, …])	Returns a signal with the signal click placed at each specified time

Spectral representations

stft(y[, n_fft, hop_length, win_length, …])	Short-time Fourier transform (STFT)
istft(stft_matrix[, hop_length, win_length, …])	Inverse short-time Fourier transform (ISTFT).
ifgram(y[, sr, n_fft, hop_length, …])	Compute the instantaneous frequency (as a proportion of the sampling rate) obtained as the time-derivative of the phase of the complex spectrum as described by [Ra44d590316d7-1].
cqt(y[, sr, hop_length, fmin, n_bins, …])	Compute the constant-Q transform of an audio signal.
icqt(C[, sr, hop_length, fmin, …])	Compute the inverse constant-Q transform.
hybrid_cqt(y[, sr, hop_length, fmin, …])	Compute the hybrid constant-Q transform of an audio signal.
pseudo_cqt(y[, sr, hop_length, fmin, …])	Compute the pseudo constant-Q transform of an audio signal.
iirt(y[, sr, win_length, hop_length, …])	Time-frequency representation using IIR filters [Rd4077732470d-1].
fmt(y[, t_min, n_fmt, kind, beta, …])	The fast Mellin transform (FMT) [R6343f8d4cac9-1] of a uniformly sampled signal y.
interp_harmonics(x, freqs, h_range[, kind, …])	Compute the energy at harmonics of time-frequency representation.
salience(S, freqs, h_range[, weights, …])	Harmonic salience function.
phase_vocoder(D, rate[, hop_length])	Phase vocoder.
magphase(D[, power])	Separate a complex-valued spectrogram D into its magnitude (S) and phase (P) components, so that D = S * P.

Magnitude scaling

amplitude_to_db(S[, ref, amin, top_db])	Convert an amplitude spectrogram to dB-scaled spectrogram.
db_to_amplitude(S_db[, ref])	Convert a dB-scaled spectrogram to an amplitude spectrogram.
power_to_db(S[, ref, amin, top_db])	Convert a power spectrogram (amplitude squared) to decibel (dB) units
db_to_power(S_db[, ref])	Convert a dB-scale spectrogram to a power spectrogram.
perceptual_weighting(S, frequencies, **kwargs)	Perceptual weighting of a power spectrogram:
A_weighting(frequencies[, min_db])	Compute the A-weighting of a set of frequencies.

Time and frequency conversion

frames_to_samples(frames[, hop_length, n_fft])	Converts frame indices to audio sample indices
frames_to_time(frames[, sr, hop_length, n_fft])	Converts frame counts to time (seconds)
samples_to_frames(samples[, hop_length, n_fft])	Converts sample indices into STFT frames.
samples_to_time(samples[, sr])	Convert sample indices to time (in seconds).
time_to_frames(times[, sr, hop_length, n_fft])	Converts time stamps into STFT frames.
time_to_samples(times[, sr])	Convert timestamps (in seconds) to sample indices.
hz_to_note(frequencies, **kwargs)	Convert one or more frequencies (in Hz) to the nearest note names.
hz_to_midi(frequencies)	Get MIDI note number(s) for given frequencies
midi_to_hz(notes)	Get the frequency (Hz) of MIDI note(s)
midi_to_note(midi[, octave, cents])	Convert one or more MIDI numbers to note strings.
note_to_hz(note, **kwargs)	Convert one or more note names to frequency (Hz)
note_to_midi(note[, round_midi])	Convert one or more spelled notes to MIDI number(s).
hz_to_mel(frequencies[, htk])	Convert Hz to Mels
hz_to_octs(frequencies[, A440])	Convert frequencies (Hz) to (fractional) octave numbers.
mel_to_hz(mels[, htk])	Convert mel bin numbers to frequencies
octs_to_hz(octs[, A440])	Convert octaves numbers to frequencies.
fft_frequencies([sr, n_fft])	Alternative implementation of np.fft.fftfreqs
cqt_frequencies(n_bins, fmin[, …])	Compute the center frequencies of Constant-Q bins.
mel_frequencies([n_mels, fmin, fmax, htk])	Compute the center frequencies of mel bands.
tempo_frequencies(n_bins[, hop_length, sr])	Compute the frequencies (in beats-per-minute) corresponding to an onset auto-correlation or tempogram matrix.

Pitch and tuning

estimate_tuning([y, sr, S, n_fft, …])	Estimate the tuning of an audio time series or spectrogram input.
pitch_tuning(frequencies[, resolution, …])	Given a collection of pitches, estimate its tuning offset (in fractions of a bin) relative to A440=440.0Hz.
piptrack([y, sr, S, n_fft, hop_length, …])	Pitch tracking on thresholded parabolically-interpolated STFT

Dynamic Time Warping

dtw([X, Y, C, metric, step_sizes_sigma, …])	Dynamic time warping (DTW).
fill_off_diagonal(x, radius[, value])	Sets all cells of a matrix to a given value if they lie outside a constraint region.