nnAudio.Spectrogram.CQT1992

class nnAudio.Spectrogram.CQT1992(sr=22050, hop_length=512, fmin=220, fmax=None, n_bins=84, trainable_STFT=False, trainable_CQT=False, bins_per_octave=12, filter_scale=1, output_format='Magnitude', norm=1, window='hann', center=True, pad_mode='reflect')

Bases: torch.nn.modules.module.Module

This alogrithm uses the method proposed in [1], which would run extremely slow if low frequencies (below 220Hz) are included in the frequency bins. Please refer to CQT1992v2() for a more computational and memory efficient version. [1] Brown, Judith C.C. and Miller Puckette. “An efficient algorithm for the calculation of a constant Q transform.” (1992).

This function is to calculate the CQT of the input signal. Input signal should be in either of the following shapes.

  1. (len_audio)

  2. (num_audio, len_audio)

  3. (num_audio, 1, len_audio)

The correct shape will be inferred autommatically if the input follows these 3 shapes. Most of the arguments follow the convention from librosa. This class inherits from torch.nn.Module, therefore, the usage is same as torch.nn.Module.

Parameters

  • sr (int) – The sampling rate for the input audio. It is used to calucate the correct fmin and fmax. Setting the correct sampling rate is very important for calculating the correct frequency.

  • hop_length (int) – The hop (or stride) size. Default value is 512.

  • fmin (float) – The frequency for the lowest CQT bin. Default is 32.70Hz, which coresponds to the note C0.

  • fmax (float) – The frequency for the highest CQT bin. Default is None, therefore the higest CQT bin is inferred from the n_bins and bins_per_octave. If fmax is not None, then the argument n_bins will be ignored and n_bins will be calculated automatically. Default is None

  • n_bins (int) – The total numbers of CQT bins. Default is 84. Will be ignored if fmax is not None.

  • bins_per_octave (int) – Number of bins per octave. Default is 12.

  • trainable_STFT (bool) – Determine if the time to frequency domain transformation kernel for the input audio is trainable or not. Default is False

  • trainable_CQT (bool) – Determine if the frequency domain CQT kernel is trainable or not. Default is False

  • norm (int) – Normalization for the CQT kernels. 1 means L1 normalization, and 2 means L2 normalization. Default is 1, which is same as the normalization used in librosa.

  • window (str) – The windowing function for CQT. It uses scipy.signal.get_window, please refer to scipy documentation for possible windowing functions. The default value is ‘hann’.

  • center (bool) – Putting the CQT keneral at the center of the time-step or not. If False, the time index is the beginning of the CQT kernel, if True, the time index is the center of the CQT kernel. Default value if True.

  • pad_mode (str) – The padding method. Default value is ‘reflect’.

  • trainable (bool) –

    Determine if the CQT kernels are trainable or not. If True, the gradients for CQT kernels

    will also be caluclated and the CQT kernels will be updated during model training. Default value is False.

    output_formatstr

    Determine the return type. Magnitude will return the magnitude of the STFT result, shape = (num_samples, freq_bins,time_steps); Complex will return the STFT result in complex number, shape = (num_samples, freq_bins,time_steps, 2); Phase will return the phase of the STFT reuslt, shape = (num_samples, freq_bins,time_steps, 2). The complex number is stored as (real, imag) in the last axis. Default value is ‘Magnitude’.

  • verbose (bool) – If True, it shows layer information. If False, it suppresses all prints

Returns

  • spectrogram (torch.tensor)

  • It returns a tensor of spectrograms.

  • shape = (num_samples, freq_bins,time_steps) if output_format='Magnitude';

  • shape = (num_samples, freq_bins,time_steps, 2) if output_format='Complex' or 'Phase';

Examples

>>> spec_layer = Spectrogram.CQT1992v2()
>>> specs = spec_layer(x)

Methods

__init__

Initializes internal Module state, shared by both nn.Module and ScriptModule.

extra_repr

Set the extra representation of the module

forward

Convert a batch of waveforms to CQT spectrograms.
extra_repr() → str

Set the extra representation of the module

To print customized extra information, you should reimplement this method in your own modules. Both single-line and multi-line strings are acceptable.

forward(x, output_format=None, normalization_type='librosa')

Convert a batch of waveforms to CQT spectrograms.

Parameters

x (torch tensor) –

Input signal should be in either of the following shapes.

  1. (len_audio)

  2. (num_audio, len_audio)

3. (num_audio, 1, len_audio) It will be automatically broadcast to the right shape