pyqtgraph live running spectrogram from microphone

livespec.py

import numpy as np
import pyqtgraph as pg
from matplotlib import cm
import pyaudio
from PyQt5 import QtCore, QtGui

FS = 48000 #Hz
CHUNKSZ = 1024 #samples

class MicrophoneRecorder():
    def __init__(self, signal):
        self.signal = signal
        self.p = pyaudio.PyAudio()
        self.stream = self.p.open(format=pyaudio.paInt16,
                            channels=1,
                            rate=FS,
                            input=True,
                            frames_per_buffer=CHUNKSZ)

    def read(self):
        data = self.stream.read(CHUNKSZ, exception_on_overflow=False)
        y = np.fromstring(data, 'int16')
        self.signal.emit(y)

    def close(self):
        self.stream.stop_stream()
        self.stream.close()
        self.p.terminate()

class SpectrogramWidget(pg.PlotWidget):
    read_collected = QtCore.pyqtSignal(np.ndarray)
    def __init__(self):
        super(SpectrogramWidget, self).__init__()

        self.img = pg.ImageItem()
        self.addItem(self.img)

        self.img_array = np.zeros((1000, int(CHUNKSZ/2+1)))

        # colormap
        colormap = cm.get_cmap("CMRmap")
        colormap._init()
        lut = (colormap._lut * 255).view(np.ndarray)

        # set colormap
        self.img.setLookupTable(lut)
        self.img.setLevels([-0,75])

        # setup the correct scaling for y-axis
        freq = np.arange((CHUNKSZ/2)+1)/(float(CHUNKSZ)/FS)
        yscale = 1/(self.img_array.shape[1]/freq[-1])
        self.img.scale((1./FS)*CHUNKSZ, yscale)

        self.setLabel('left', 'Frequency', units='Hz')

        # prepare window for later use
        self.win = np.hanning(CHUNKSZ)
        self.show()

    def update(self, chunk):
        # normalized, windowed frequencies in data chunk
        spec = np.fft.rfft(chunk*self.win) / CHUNKSZ
        # get magnitude
        psd = abs(spec)
        # convert to dB scale
        psd = 20 * np.log10(psd)

        # roll down one and replace leading edge with new data
        self.img_array = np.roll(self.img_array, -1, 0)
        self.img_array[-1:] = psd

        self.img.setImage(self.img_array, autoLevels=False)

if __name__ == '__main__':
    app = QtGui.QApplication([])
    w = SpectrogramWidget()
    w.read_collected.connect(w.update)

    mic = MicrophoneRecorder(w.read_collected)

    # time (seconds) between reads
    interval = FS/2*CHUNKSZ
    t = QtCore.QTimer()
    t.timeout.connect(mic.read)
    t.start(int(1000/interval)) #QTimer takes ms

    app.exec_()
    mic.close()