Change default value of dither

[vincentqb]

Following comment, setting dither to 0 and setting energy_floor to 1..

import torchaudio

filename = "audio/test/assets/steam-train-whistle-daniel_simon.mp3"
s, sr = torchaudio.load(filename)

spec1 = torchaudio.compliance.kaldi.spectrogram(s, dither=0., energy_floor=1.)
spec2 = torchaudio.compliance.kaldi.spectrogram(s, dither=1e-6)
print(2*((spec1 - spec2).abs()/(spec1.abs() + spec2.abs())).mean())
# tensor(0.0016)  # Mean absolute percent difference 

spec1 = torchaudio.compliance.kaldi.fbank(s, dither=0., energy_floor=1.)
spec2 = torchaudio.compliance.kaldi.fbank(s, dither=1e-6)
print(2*((spec1 - spec2).abs()/(spec1.abs() + spec2.abs())).mean())
# tensor(4.8548e-05)

spec1 = torchaudio.compliance.kaldi.mfcc(s, dither=0., energy_floor=1.)
spec2 = torchaudio.compliance.kaldi.mfcc(s, dither=1e-6)
print(2*((spec1 - spec2).abs()/(spec1.abs() + spec2.abs())).mean())
# tensor(0.0022)

Closes #371

[zhangguanheng66]

Update docs?

[vincentqb]

Update docs?

Thanks, good catch! Updated.