Lower the priority of Bluetooth mic even in wideband

Bug: b/156333981
Change-Id: Ieec9421a98119684f3ad901b16c1ad8dbe8998ef
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2196082Reviewed-by: Jenny Zhang <jennyz@chromium.org>
Commit-Queue: Hsinyu Chao <hychao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#772093}

chromeos/audio/audio_device.cc

@@ -18,11 +18,19 @@ namespace {
 // Get the priority for a particular device type. The priority returned
 // will be between 0 to 3, the higher number meaning a higher priority.
 uint8_t GetDevicePriority(AudioDeviceType type, bool is_input) {
+  // Lower the priority of bluetooth wide band mic. Although the quality is
+  // better than narrow band(AUDIO_TYPE_BLUETOOTH_NB_MIC), we still want
+  // to avoid auto-selecting Bluetooth mic when there is another audio input
+  // option.
+  if (type == AUDIO_TYPE_BLUETOOTH && is_input)
+    return 0;
   switch (type) {
     case AUDIO_TYPE_HEADPHONE:
     case AUDIO_TYPE_LINEOUT:
     case AUDIO_TYPE_MIC:
     case AUDIO_TYPE_USB:
+    // This is for bluetooth output node. Bluetooth inputs(wide band and narrow
+    // band mic) are handled separately.
     case AUDIO_TYPE_BLUETOOTH:
       return 3;
     case AUDIO_TYPE_HDMI: