CODEWITHSUNDEEP
pythonpython-2.7signalssignal-processingfft
Hanna
Hanna

Reputation: 53

how to get phase fft of a signal &-- can i get phase in time domain?

i can get magnitude of signal coming from .wav file , but how to get the phase of that signal too ,,, Here is the where i browse for .wav file and extract the signal 

def browse_wav(self):

    filepath = QtGui.QFileDialog.getOpenFileName(self, 'Single File', "C:\Users\Hanna Nabil\Documents",'*.wav')
    f= str(filepath)
    if f != "":
        spf = wave.open(f, 'r')
    import contextlib

    with contextlib.closing(wave.open(f, 'r')) as f:
        frames = f.getnframes()
        rate = f.getframerate()
        duration = frames / float(rate)
        print "Duration is " , duration

    # Extract Raw Audio from Wav File
    self.signal = spf.readframes(-1)
    self.signal = np.fromstring(self.signal, 'Int16')
    self.fs = spf.getframerate()
    print "Sampling Rate is " ,self.fs

    # If Stereo
    if spf.getnchannels() == 2:
        print 'Just mono files'
        sys.exit(0)

    #self.time = np.linspace(0, len(self.signal) / fs, num=len(self.signal))
    self.time = np.linspace(0, duration, self.fs * duration)

    self.xfourier = fftfreq(self.signal.size, d=self.time[1] - self.time[0])
    self.yfourier = np.abs(fft(self.signal))  # signal magnitude

    self.zico = self.yfourier
    self.cut_signal = ifft(self.zico)

Upvotes: 5

Views: 22109

Answers (2)

Phillip Otey
Phillip Otey

Reputation: 29

For the answer from Lukas Lalinsky I find I have to add pi/2 for some reason to get the correct answer.

Also for points:

N = len(t)
Amplitude = 2/N *  np.abs(magnitude)

Upvotes: -1

Lukáš Lalinský
Lukáš Lalinský

Reputation: 41306

The complex spectrum contains both the magnitude and phase. You get the magnitude by calculating the absolute value and you get the phase by calculating the angle. You can use numpy.angle() to get the phase:

spectrum = fft(self.signal)
magnitude = np.abs(spectrum)
phase = np.angle(spectrum)

Upvotes: 12

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