librosa.core.phase_vocoder¶
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librosa.core.
phase_vocoder
(D, rate, hop_length=None)[source]¶ Phase vocoder. Given an STFT matrix D, speed up by a factor of rate
Based on the implementation provided by [1].
[1] Ellis, D. P. W. “A phase vocoder in Matlab.” Columbia University, 2002. http://www.ee.columbia.edu/~dpwe/resources/matlab/pvoc/ Parameters: - D : np.ndarray [shape=(d, t), dtype=complex]
STFT matrix
- rate : float > 0 [scalar]
Speed-up factor: rate > 1 is faster, rate < 1 is slower.
- hop_length : int > 0 [scalar] or None
The number of samples between successive columns of D.
If None, defaults to n_fft/4 = (D.shape[0]-1)/2
Returns: - D_stretched : np.ndarray [shape=(d, t / rate), dtype=complex]
time-stretched STFT
Examples
>>> # Play at double speed >>> y, sr = librosa.load(librosa.util.example_audio_file()) >>> D = librosa.stft(y, n_fft=2048, hop_length=512) >>> D_fast = librosa.phase_vocoder(D, 2.0, hop_length=512) >>> y_fast = librosa.istft(D_fast, hop_length=512)
>>> # Or play at 1/3 speed >>> y, sr = librosa.load(librosa.util.example_audio_file()) >>> D = librosa.stft(y, n_fft=2048, hop_length=512) >>> D_slow = librosa.phase_vocoder(D, 1./3, hop_length=512) >>> y_slow = librosa.istft(D_slow, hop_length=512)