CODEWITHSUNDEEP
pythonaudiosignal-processing
Majid
Majid

Reputation: 261

Plot spectogram from mp3

I am trying to plot a spectogram straight from an mp3 file in python 2.7.3 (using ubuntu). I can do it from a wav file as follows.

#!/usr/bin/python
from scikits.audiolab import wavread
from pylab import *

signal, fs, enc = wavread('XC124158.wav')
specgram(signal)
show()

What's the cleanest way to do the same thing from an mp3 file instead of a wav? I don't want to convert all the mp3 files to wav if I can avoid it.

Upvotes: 6

Views: 15747

Answers (2)

dsalaj
dsalaj

Reputation: 3207

Another very simple way of plotting spectrogram of mp3 file.

from pydub import AudioSegment
import matplotlib.pyplot as plt
from scipy.io import wavfile
from tempfile import mktemp

mp3_audio = AudioSegment.from_file('speech.mp3', format="mp3")  # read mp3
wname = mktemp('.wav')  # use temporary file
mp3_audio.export(wname, format="wav")  # convert to wav
FS, data = wavfile.read(wname)  # read wav file
plt.specgram(data, Fs=FS, NFFT=128, noverlap=0)  # plot
plt.show()

This uses the pydub library which is more convenient compared to calling external commands. This way you can iterate over all your .mp3 files without having to convert them to .wav prior to plotting.

enter image description here

Upvotes: 13

Eryk Sun
Eryk Sun

Reputation: 34270

I'd install the Debian/Ubuntu package libav-tools and call avconv to decode the mp3 to a temporary wav file:

Edit: Your other question was closed, so I'll expand my answer here a bit with a simple bandpass filtering example. In the file you linked it looks like most of the birdsong is concentrated in 4 kHz - 5.5 kHz.

import os
from subprocess import check_call
from tempfile import mktemp
from scikits.audiolab import wavread, play
from scipy.signal import remez, lfilter
from pylab import *

# convert mp3, read wav
mp3filename = 'XC124158.mp3'
wname = mktemp('.wav')
check_call(['avconv', '-i', mp3filename, wname])
sig, fs, enc = wavread(wname)
os.unlink(wname)

# bandpass filter
bands = array([0,3500,4000,5500,6000,fs/2.0]) / fs
desired = [0, 1, 0]
b = remez(513, bands, desired)
sig_filt = lfilter(b, 1, sig)
sig_filt /=  1.05 * max(abs(sig_filt)) # normalize

subplot(211)
specgram(sig, Fs=fs, NFFT=1024, noverlap=0)
axis('tight'); axis(ymax=8000)
title('Original')
subplot(212)
specgram(sig_filt, Fs=fs, NFFT=1024, noverlap=0)
axis('tight'); axis(ymax=8000)
title('Filtered')
show()

play(sig_filt, fs)

Bird Song Spectrgrams

Upvotes: 9

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