pyqtgraph live running spectrogram from microphone

livespec.py

"""
Tested on Linux with python 3.7
Must have portaudio installed (e.g. dnf install portaudio-devel)

pip install pyqtgraph pyaudio PyQt5
"""
import numpy as np
import pyqtgraph as pg
import pyaudio
from PyQt5 import QtCore, QtGui

FS = 44100 #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)))

        # bipolar colormap
        pos = np.array([0., 1., 0.5, 0.25, 0.75])
        color = np.array([[0,255,255,255], [255,255,0,255], [0,0,0,255], (0, 0, 255, 255), (255, 0, 0, 255)], dtype=np.ubyte)
        cmap = pg.ColorMap(pos, color)
        lut = cmap.getLookupTable(0.0, 1.0, 256)

        # set colormap
        self.img.setLookupTable(lut)
        self.img.setLevels([-50,40])

        # setup the correct scaling for y-axis
        freq = np.arange((CHUNKSZ/2)+1)/(float(CHUNKSZ)/FS)
        yscale = 1.0/(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/CHUNKSZ
    t = QtCore.QTimer()
    t.timeout.connect(mic.read)
    t.start(1000/interval) #QTimer takes ms

    app.exec_()
    mic.close()

I get:
IOError: [Errno -9981] Input overflowed

and then a bunch of
IOError: [Errno -9988] Stream closed

when trying this. I've tried playing around with the chunk size, but no luck. Do you find this still works with modern pyqt ?

@rxa254, update Pyaudio to the latest version and give the parameter in read() method like this : data = stream.read(CHUNK, exception_on_overflow=False)

I changed the from PyQt4 in line 4 to from PyQt5, added the above mentioned exception_on_overflow=False) to line 20

And added int to line 37:
self.img_array = np.zeros((1000, int(CHUNKSZ/2+1)))
and it works!

You can use colormaps from matplotlib:

from matplotlib import cm

# 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])

I finally got around to firing this up again and updated the gist with the suggested fixes, thanks @pranav6670 and @conraddisc !

Also thanks for the comment about using matplotlib's pre-defined maps @AB9IL

Can someone please add a pictures of the result?

I discovered today after upgrading to matplotlib 3.7.1 to get colormaps like Turbo that I needed to update line 1084 in /usr/lib/python3/dist-packages/pyqtgraph/functions.py with the following

levels = levels.astype(float)
instead of
levels = levels.astype(np.float)

as it has been depreciated

looks great and works again
The photo is live audio from Dallas Love Field showing realtime spectrographs of aircraft taking off and their distinct audio signatures.

Does this still work? I installed pyqt5 but I get this error when I try to run it:

AttributeError: module 'PyQt5.QtGui' has no attribute 'QApplication'. Did you mean: 'QGuiApplication'?

Does this still work? I installed pyqt5 but I get this error when I try to run it:

AttributeError: module 'PyQt5.QtGui' has no attribute 'QApplication'. Did you mean: 'QGuiApplication'?

Yes, using 'QGuiApplication' fixed that error. I had a separate issue, getting a message:

Unable to locate theme engine in module_path: "adwaita"

...which cleared after installing gnome-themes-standard

If you find Qt5 is out of date, pip installing pyside2 will fix that, but it is a large download.

I tried QGuiApplication, but it didn't work. What got it working for me was switching to:

app = QtWidgets.QApplication([])

I'm having trouble with the scaling. Is this a Pyqt version problem?

  File "livespec.py", line 142, in __init__
    self.img.setScale((1./FS)*CHUNKSZ, yscale)
TypeError: setScale(self, scale: float): too many arguments

I also had this problem. I had to switch to using:

self.img.setTransform(QtGui.QTransform.fromScale((1./samplerate)*samplesize, yscale))

I'm not sure if it does the exact same thing but it seems to work.

Awesome tool. I am wondering if there is a way to an interactive color bar. Any help would be appreciated. Thanks