fix: disallow selecting non-microphone audio device

Previously any audio device was allowed to be selected as microphone. Now, only ones with at least one input channel can be selected.

ref: N25B-119

src/robot_interface/utils/microphone.py

@@ -1,8 +1,25 @@
+from __future__ import unicode_literals  # So that `print` can print the Unicode strings in names
 import logging
 
 logger = logging.getLogger(__name__)
 
 
+def get_microphones(audio):
+    """
+    Get audio devices which have input channels.
+
+    :param audio: An instance of PyAudio to use.
+    :type audio: pyaudio.PyAudio
+
+    :return: An interator of PaAudio dicts containing information about the microphone devices.
+    :rtype: Iterator[dict]
+    """
+    for i in range(audio.get_device_count()):
+        device = audio.get_device_info_by_index(i)
+        if device["maxInputChannels"] > 0:
+            yield device
+
+
 def choose_mic_interactive(audio):
     """
     Choose a microphone to use, interactively in the CLI.
@@ -14,24 +31,23 @@ def choose_mic_interactive(audio):
     if there is no microphone.
     :rtype: dict | None
     """
-    device_count = audio.get_device_count()
-    if device_count == 0: return None
+    microphones = list(get_microphones(audio))
+    if len(microphones) == 0: return None
 
-    print("Found {} audio devices:".format(device_count))
-    for i in range(device_count):
-        print("- {}: {}".format(i, audio.get_device_info_by_index(i)["name"]))
+    print("Found {} microphones:".format(len(microphones)))
+    for i, mic in enumerate(microphones):
+        print("- {}: {}".format(i, mic["name"]))
 
-    microphone_index = None
-    while microphone_index is None:
+    chosen_microphone = None
+    while chosen_microphone is None:
         chosen = raw_input("Which device would you like to use?\n> ")
         try:
             chosen = int(chosen)
-            if chosen < 0 or chosen >= device_count: raise ValueError()
-            microphone_index = chosen
+            if chosen < 0 or chosen >= len(microphones): raise ValueError()
+            chosen_microphone = microphones[chosen]
         except ValueError:
-            print("Please enter a number between 0 and {}".format(device_count-1))
+            print("Please enter a number between 0 and {}".format(len(microphones)-1))
 
-    chosen_microphone = audio.get_device_info_by_index(microphone_index)
     logger.info("Chose microphone \"{}\"".format(chosen_microphone["name"]))
     return chosen_microphone
 
@@ -47,8 +63,7 @@ def choose_mic_default(audio):
     if there is no microphone.
     :rtype: dict | None
     """
-    device_count = audio.get_device_count()
-    if device_count == 0: return None
-
-    default_device = audio.get_default_input_device_info()
-    return default_device
+    try:
+        return audio.get_default_input_device_info()
+    except IOError:
+        return None