:orphan:

spectrum
--------


Sample microphone input and display power spectrum

.. raw:: html

  <video width="558" height="558" controls autoplay>
    <source src="../_static/examples/spectrum.mov" type="video/mp4">
    <source src="../_static/examples/spectrum.ogg" type="video/ogg">
  </video>

----

.. code-block:: python
    
    
    
    from __future__ import print_function
    
    import pyaudio
    import numpy as np
    from scipy import signal
    import time
    import gr
    
    FS = 44100  # Sampling frequency
    SAMPLES = 4096
    
    mic = None
    
    
    def get_spectrum():
        global mic
        if mic is None:
            pa = pyaudio.PyAudio()
            mic = pa.open(format=pyaudio.paInt16, channels=1, rate=FS,
                          input=True, frames_per_buffer=SAMPLES)
        amplitudes = np.frombuffer(mic.read(SAMPLES), dtype=np.short)
        return abs(np.fft.fft(amplitudes / 32768.0))[:SAMPLES // 2]
    
    
    def parabolic(x, f, i):
        xe = 1 / 2. * (f[i - 1] - f[i + 1]) / (f[i - 1] - 2 * f[i] + f[i + 1]) + x
        ye = f[i] - 1 / 4. * (f[i - 1] - f[i + 1]) * (xe - x)
        return xe, ye
    
    
    f = [FS / float(SAMPLES) * t for t in range(0, SAMPLES // 2)]
    
    gr.setviewport(0.1, 0.95, 0.1, 0.95)
    gr.setwindow(50, 25000, 0, 100)
    gr.setscale(1)
    
    start = time.time()
    
    while time.time() - start < 10:
        try:
            power = get_spectrum()
            peakind = signal.find_peaks_cwt(power, np.array([5]))
        except (IOError):
            continue
    
        gr.clearws()
        gr.setlinewidth(1)
        gr.setlinecolorind(1)
        gr.grid(1, 5, 50, 0, 1, 2)
        gr.axes(1, 5, 50, 0, 1, 2, -0.008)
        gr.setcharheight(0.020)
        gr.text(0.15, 0.965, '100Hz')
        gr.text(0.47, 0.965, '1kHz')
        gr.text(0.79, 0.965, '10kHz')
        gr.setlinecolorind(4)
        gr.polyline(f[1:], power[1:])
        for p in peakind:
            if power[p] > 10:
                gr.setlinewidth(2)
                gr.setlinecolorind(2)
                xe, ye = parabolic(f[p], power, p)
                print(xe, ye)
                gr.polyline([xe] * 2, [0, ye])
        gr.updatews()