Change microphone.py, decodes data before callback

Microphone.py is now responsible for decoding audio data. The decoded data now passed to the callback function

python/microphone.py

@@ -1,16 +1,29 @@
+import time
+import numpy as np
 import pyaudio
 import config
 
 
 def start_stream(callback):
     p = pyaudio.PyAudio()
+    frames_per_buffer = int(config.MIC_RATE / config.FPS)
     stream = p.open(format=pyaudio.paInt16,
                     channels=1,
                     rate=config.MIC_RATE,
                     input=True,
-                    frames_per_buffer=int(config.MIC_RATE / config.FPS))
+                    frames_per_buffer=frames_per_buffer)
+    overflows = 0
+    prev_ovf_time = time.time()
     while True:
-        callback(stream)
+        try:
+            y = np.fromstring(stream.read(frames_per_buffer), dtype=np.int16)
+            y = y.astype(np.float32)
+            callback(y)
+        except IOError:
+            overflows += 1
+            if time.time() > prev_ovf_time + 1:
+                prev_ovf_time = time.time()
+                print('Audio buffer has overflowed {} times'.format(overflows))
     stream.stop_stream()
     stream.close()
     p.terminate()