pythonaudiospectrogramlibrosa

Why spectrogram from librosa library have twice the time duration of the actual audio track?

I am using the following code to obtain Mel spectrogram from a recorded audio signal of about 30 s:

spectrogram =  librosa.feature.melspectrogram(y=self.RawSamples,sr=self.SamplingFrequency, n_mels=128, fmax=8000)

if show:
    plt.figure(figsize=(10, 4))
    librosa.display.specshow(librosa.power_to_db(self.Spectrogram, ref=np.max), y_axis='mel', fmax=8000, x_axis='time')
    plt.colorbar(format='%+2.0f dB')
    plt.title('Mel spectrogram')
    plt.tight_layout()

Obtained spectrogram: Mel spectrogram

Can you please explain me why the time axis depicts twice the time duration (it should be 30 s). What is going wrong with the code?

Solution

  • You need to pass the sampling rate to librosa.display.specshow (sr=self.SamplingFrequency). If not it defaults to 20050 and if self.SamplingFrequency is a different value, it will display the wrong length.