Add support for audio input mute detection on all platforms

media/audio/mac/audio_low_latency_input_mac.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "media/audio/mac/audio_low_latency_input_mac.h"
 
 #include <CoreServices/CoreServices.h>
 
 #include "base/basictypes.h"
 #include "base/logging.h"
@@ skipping 433 matching lines @@
 
     // Get the average volume of the channels.
     if (successful_channels != 0)
       return static_cast<double>(volume_float32 / successful_channels);
   }
 
   DLOG(WARNING) << "Failed to get volume";
   return 0.0;
 }
 
+bool AUAudioInputStream::IsMuted() {
+  // Verify that we have a valid device.
+  if (input_device_id_ == kAudioObjectUnknown) {
+    NOTREACHED() << "Device ID is unknown";

[tommi (sloooow) - chröme, 2014/10/15 17:00:48]

should this be a DCHECK then?

DCHECK_NE(input_device_id_, kAudioObjectUnknown)

+    return false;
+  }
+
+  AudioObjectPropertyAddress property_address = {
+      kAudioDevicePropertyMute,

[tommi (sloooow) - chröme, 2014/10/15 17:00:48]

nit: indent by two spaces and put the closing brace on a line of its own (see
elsewhere in this file)

[henrika (OOO until Aug 14), 2014/10/16 09:58:00]

Done.

+      kAudioDevicePropertyScopeInput,
+      kAudioObjectPropertyElementMaster};
+
+  if (!AudioObjectHasProperty(input_device_id_, &property_address)) {
+    NOTREACHED() << "Device does not support checking master mute state";

[tommi (sloooow) - chröme, 2014/10/15 17:00:48]

since NOTREACHED is essentially the same as DCHECK, I'm wondering if this should
perhaps rather be a DLOG(ERROR)?

[henrika (OOO until Aug 14), 2014/10/16 09:58:00]

Done.

+    return false;
+  }
+
+  UInt32 muted = 0;
+  UInt32 size = sizeof(muted);
+  OSStatus result = AudioObjectGetPropertyData(
+      input_device_id_, &property_address, 0, NULL, &size, &muted);
+  if (result == noErr)
+    return static_cast<bool>(muted);

[tommi (sloooow) - chröme, 2014/10/15 17:00:48]

nit: return muted != 0u;

actually, you could also just do:

DLOG_IF(WARNING, result != noErr) << "Failed to get mute state";
return result == noErr && muted != 0;

[henrika (OOO until Aug 14), 2014/10/16 09:58:00]

Done.

+
+  DLOG(WARNING) << "Failed to get mute state";
+  return false;
+}
+
 // AUHAL AudioDeviceOutput unit callback
 OSStatus AUAudioInputStream::InputProc(void* user_data,
                                        AudioUnitRenderActionFlags* flags,
                                        const AudioTimeStamp* time_stamp,
                                        UInt32 bus_number,
                                        UInt32 number_of_frames,
                                        AudioBufferList* io_data) {
   // Verify that the correct bus is used (Input bus/Element 1)
   DCHECK_EQ(bus_number, static_cast<UInt32>(1));
   AUAudioInputStream* audio_input =
@@ skipping 183 matching lines @@
     kAudioDevicePropertyScopeInput,
     static_cast<UInt32>(channel)
   };
   OSStatus result = AudioObjectIsPropertySettable(input_device_id_,
                                                   &property_address,
                                                   &is_settable);
   return (result == noErr) ? is_settable : false;
 }
 
 }  // namespace media