torchaudio.functional.phase_vocoder

torchaudio.functional.phase_vocoder(complex_specgrams: Tensor, rate: float, phase_advance: Tensor) → Tensor

Given a STFT tensor, speed up in time without modifying pitch by a factor of rate.

Parameters

• complex_specgrams (Tensor) – A tensor of dimension (…, freq, num_frame) with complex dtype.

• rate (float) – Speed-up factor

• phase_advance (Tensor) – Expected phase advance in each bin. Dimension of (freq, 1)

Returns

Stretched spectrogram. The resulting tensor is of the same dtype as the input spectrogram, but the number of frames is changed to ceil(num_frame / rate).

Return type

Tensor

Example

>>> freq, hop_length = 1025, 512
>>> # (channel, freq, time)
>>> complex_specgrams = torch.randn(2, freq, 300, dtype=torch.cfloat)
>>> rate = 1.3 # Speed up by 30%
>>> phase_advance = torch.linspace(
>>>    0, math.pi * hop_length, freq)[..., None]
>>> x = phase_vocoder(complex_specgrams, rate, phase_advance)
>>> x.shape # with 231 == ceil(300 / 1.3)
torch.Size([2, 1025, 231])