Micd: update sound levels in callback

system/micd.py

@@ -9,6 +9,7 @@
 
 RATE = 10
 DT_MIC = 1. / RATE
+FFT_SAMPLES = 4096
 REFERENCE_SPL = 2e-5  # newtons/m^2
 SAMPLE_RATE = 44100
 
@@ -45,41 +46,46 @@ def __init__(self, pm):
     self.rk = Ratekeeper(RATE)
 
     self.measurements = np.empty(0)
-    self.spl_filter_weighted = FirstOrderFilter(0, 2.5, DT_MIC, initialized=False)
 
-  def update(self):
-    """
-    Using amplitude measurements, calculate an uncalibrated sound pressure and sound pressure level.
-    Then apply A-weighting to the raw amplitudes and run the same calculations again.
+    self.sound_pressure = 0
+    self.sound_pressure_weighted = 0
+    self.sound_pressure_level_weighted = 0
 
-    Logged A-weighted equivalents are rough approximations of the human-perceived loudness.
-    """
-
-    if len(self.measurements) > 0:
-      sound_pressure, _ = calculate_spl(self.measurements)
-      measurements_weighted = apply_a_weighting(self.measurements)
-      sound_pressure_weighted, sound_pressure_level_weighted = calculate_spl(measurements_weighted)
-      self.spl_filter_weighted.update(sound_pressure_level_weighted)
-    else:
-      sound_pressure = 0
-      sound_pressure_weighted = 0
-      sound_pressure_level_weighted = 0
+    self.spl_filter_weighted = FirstOrderFilter(0, 2.5, DT_MIC, initialized=False)
 
-    self.measurements = np.empty(0)
+  def update(self):
+    if self.sound_pressure_level_weighted != 0:
+      self.spl_filter_weighted.update(self.sound_pressure_level_weighted)
 
     msg = messaging.new_message('microphone')
-    msg.microphone.soundPressure = float(sound_pressure)
-    msg.microphone.soundPressureWeighted = float(sound_pressure_weighted)
+    msg.microphone.soundPressure = float(self.sound_pressure)
+    msg.microphone.soundPressureWeighted = float(self.sound_pressure_weighted)
 
-    msg.microphone.soundPressureWeightedDb = float(sound_pressure_level_weighted)
+    msg.microphone.soundPressureWeightedDb = float(self.sound_pressure_level_weighted)
     msg.microphone.filteredSoundPressureWeightedDb = float(self.spl_filter_weighted.x)
 
     self.pm.send('microphone', msg)
     self.rk.keep_time()
 
   def callback(self, indata, frames, time, status):
+    """
+    Using amplitude measurements, calculate an uncalibrated sound pressure and sound pressure level.
+    Then apply A-weighting to the raw amplitudes and run the same calculations again.
+
+    Logged A-weighted equivalents are rough approximations of the human-perceived loudness.
+    """
+
     self.measurements = np.concatenate((self.measurements, indata[:, 0]))
 
+    while self.measurements.size >= FFT_SAMPLES:
+      measurements = self.measurements[:FFT_SAMPLES]
+
+      self.sound_pressure, _ = calculate_spl(measurements)
+      measurements_weighted = apply_a_weighting(measurements)
+      self.sound_pressure_weighted, self.sound_pressure_level_weighted = calculate_spl(measurements_weighted)
+
+      self.measurements = self.measurements[FFT_SAMPLES:]
+
   def micd_thread(self, device=None):
     if device is None:
       device = "sysdefault"