fft_graph.py

from kivy.app import App
from kivy.clock import Clock
from kivy.uix.widget import Widget
from kivy.graphics import Color, Line
import random, time
import queue, threading

class FFTGraph(Widget):
    def draw_graph(self, dt):
        try:
            samples = self.sound_queue.get(timeout=0.1)
        except queue.Empty:
            return
       
        # Normalize the samples from screen_height to 0: 
        height = self.size[1]
        samples = [ height - int(s * height) for s in samples ]
        # Transform the samples into [(x, y),...] coords:
        lines = list(zip(range(len(samples)), samples))
        # Flatten the list:
        points = [ n for coord in lines for n in coord ]
        # Put it on the screen
        self.canvas.clear()
        with self.canvas:
            Color(1., 1., 0)
            Line(points=points, width=1)

class TestApp(App):
    def build(self):
        fft = FFTGraph()
        fft.sound_queue = self.sound_queue
        Clock.schedule_interval(fft.draw_graph, 1 / 30.)
        return fft
    
def play_sound(fft_queue):
    frame_count = 1
    while True:
        # Fetch audio chunk
        fft_bins = [] #...

        # Put frame in the queue as often as we want to draw it:
        if frame_count == 200:
            count = 1
            # 512 samples of amplitude between 0 and 1:
            fft_bins = [ random.random() for r in range(512) ]
            # If .put is too slow for audio, try put_nowait() instead
            fft_queue.put(fft_bins)
        
        # Pipe audio to sound card
        time.sleep(1.0 / 8000)
        frame_count += 1

if __name__ == '__main__':
    # Build the kivy app and pass in our Queue for sending fft bins:  
    app = TestApp()
    app.sound_queue = queue.Queue()

    # Set up our audio playing thread
    stream = threading.Thread(target=play_sound, args=(app.sound_queue,))
    stream.daemon = True
    stream.start()

    # Kick off the GUI event loop
    app.run()