Plotting audio from librosa in matplotlib

Question

I am trying to plot the waveform of an audio file in Python.

This is my code (I am using the Librosa library):

import plot as plt

def save_plot(filename):
    y, sr = librosa.load(filename)        
    plt.plot(y, 'audio', 'time', 'amplitude')

Where the plot.py file is:

import matplotlib.pylab as plt

def plot(vector, name, xlabel=None, ylabel=None):
    plt.figure()
    plt.plot(vector)
    plt.xlabel(xlabel)
    plt.ylabel(ylabel)
    plt.plot()
    plt.savefig('static/plots/' + name)

The weird thing is that, even though I get a plot that seems like a valid waveform:

The audio file is only 5 seconds long. Therefore, I don't understand what the x axis is talking about; it seems to go up to 90000?

Thanks

Answer 1

The waveform will have a data point at every time your audio file is sampled, they can be sampled from 8000 Hz to 48 kHz. 90,000\/5 = 18000 Hz.

Answer 2

This is why you're using matplotlib.pyplot<\/code> to plot your vector, which contains many terms as it (probably) samples 22050 data points per second. If you got an audio file with 5 seconds then you get 5 * 22050 = 110250 data points, which will be plotted in the figure. Instead of using matplotlib.pyplot<\/code> you can just use the proper way to do this with librosa<\/code> :

import librosa
import librosa.display

y, sr = librosa.load(<path_audio_file>, sr=<sample_rate>)
fig, ax = librosa.display.waveplot(y, sr=sr)