torchaudio.compliance.kaldi.spectrogram is very different from torchaudio.transforms.spectrogram

Does torchaudio.compliance.kaldi.spectrogram only currently support vectors?

When feeding a tensor of shape torch.Size([2, 276858]) the result is not what’s expected, yet there is no error. I would expect a “train pattern” to be visible, as in the second figure below.

This is what kaldi gives

This is what torchaudio.transforms.spectrogram gives

The “train pattern” is also visible on academo.org.

[vincentqb]

@vincentqb Can you upload the wav file again. I can not find it. The link is broken.

The file can still be accessed here.

[jamarshon]

@vincentqb I could investigate the flags more kaldi.spectrogram to get a more closer result but is this more similar to what you would expect?

import torch
import torchaudio
import matplotlib
%matplotlib inline
import matplotlib.pyplot as plt

filename = "/Users/jamarshon/Documents/GitHub/audio/test/assets/steam-train-whistle-daniel_simon.mp3"
s, sr = torchaudio.load(filename)
EPSILON = torch.tensor(torch.finfo(torch.float).eps, dtype=torch.get_default_dtype())

spec = torchaudio.transforms.Spectrogram()(s)
x = torch.max(EPSILON, spec).log2().transpose(1,2)[0,:,:]
plt.imshow(x.numpy(), cmap='gray')
plt.show()

n_fft = 400.0
fl = n_fft / sr * 1000.0
fs = fl / 2.0
spec2 = torchaudio.compliance.kaldi.spectrogram(
	s, dither=0.0, window_type='hanning', 
	frame_length=fl, frame_shift=fs, remove_dc_offset=False, 
	round_to_power_of_two=False, sample_frequency=sr)
y = spec2.t()
plt.imshow(y.numpy(), cmap='gray')
plt.show()

Spec1: Spec2: