mindspore.dataset.audio.TimeStretch

class mindspore.dataset.audio.TimeStretch(hop_length=None, n_freq=201, fixed_rate=None)[source]

Stretch Short Time Fourier Transform (STFT) in time without modifying pitch for a given rate.

Note

The shape of the audio waveform to be processed needs to be <…, freq, time, complex=2>. The first dimension represents the real part while the second represents the imaginary.

Parameters

  • hop_length (int, optional) – Length of hop between STFT windows, i.e. the number of samples between consecutive frames. Default: None, will use n_freq - 1 .

  • n_freq (int, optional) – Number of filter banks from STFT. Default: 201.

  • fixed_rate (float, optional) – Rate to speed up or slow down by. Default: None, will keep the original rate.

Raises

  • TypeError – If hop_length is not of type int.

  • ValueError – If hop_length is not a positive number.

  • TypeError – If n_freq is not of type int.

  • ValueError – If n_freq is not a positive number.

  • TypeError – If fixed_rate is not of type float.

  • ValueError – If fixed_rate is not a positive number.

  • RuntimeError – If input tensor is not in shape of <…, freq, num_frame, complex=2>.

Supported Platforms:

CPU

Examples

>>> import numpy as np
>>> import mindspore.dataset as ds
>>> import mindspore.dataset.audio as audio
>>>
>>> # Use the transform in dataset pipeline mode
>>> waveform = np.random.random([5, 16, 8, 2])  # 5 samples
>>> numpy_slices_dataset = ds.NumpySlicesDataset(data=waveform, column_names=["audio"])
>>> transforms = [audio.TimeStretch()]
>>> numpy_slices_dataset = numpy_slices_dataset.map(operations=transforms, input_columns=["audio"])
>>> for item in numpy_slices_dataset.create_dict_iterator(num_epochs=1, output_numpy=True):
...     print(item["audio"].shape, item["audio"].dtype)
...     break
(1, 16, 8, 2) float64
>>>
>>> # Use the transform in eager mode
>>> waveform = np.random.random([16, 8, 2])  # 1 sample
>>> output = audio.TimeStretch()(waveform)
>>> print(output.shape, output.dtype)
(1, 16, 8, 2) float64
Tutorial Examples: