A major direction of Deep Learning in audio, especially generative models, is using features in frequency domain because directly model raw time signal is hard. But this require an extra process to convert the predicted spectrogram (magnitude-only in most situation) back to time domain.

To help researcher no need to care this post-precessing step, this package provide some useful and classic spectrogram inversion algorithms. These algorithms are selected base on their performance and high parallelizability, and can even be integrated in your model training process.

We hope this tool can serve as a standard, making fair comparison of different audio generation models.

First Install PyTorch with the desired cpu/gpu support and version >= 0.4.1. Then install via pip

pip install torch_specinv

or

pip install git+https://github.com/yoyololicon/spectrogram-inversion

to get the latest version.

The following example estimated the time signal given only the magnitude information of an audio file.

import torch
import librosa
from torch_specinv import griffin_lim
from torch_specinv.metrics import spectral_convergence as SC

y, sr = librosa.load(librosa.util.example_audio_file())
y = torch.from_numpy(y)
windowsize = 2048
window = torch.hann_window(windowsize)
S = torch.stft(y, windowsize, window=window)

# discard phase information
mag = S.pow(2).sum(2).sqrt()

# move to gpu memory for faster computation
mag = mag.cuda()

yhat = griffin_lim(mag, maxiter=100, alpha=0.3, window=window)

# check convergence
mag_hat = torch.stft(yhat, windowsize, window=window).pow(2).sum(2).sqrt()
print(SC(mag_hat, mag))

Reconstruct from other spectral representation:

from librosa.filters import mel
from torch_specinv import L_BFGS

filter_banks = torch.from_numpy(mel(sr, windowsize)).cuda()

def trsfn(x):
    S = torch.stft(x, windowsize, window=window).pow(2).sum(2).sqrt()
    mel_S = filter_banks @ S
    return torch.log1p(mel_S)

y = y.cuda()
mag = trsfn(y)
yhat = L_BFGS(mag, trsfn, len(y))       

• Speed comparison on GPU.
• Documentation.
• Examples.