Provide isAudioEnabled flag to control audio unit.

webrtc/modules/audio_device/ios/voice_processing_audio_unit.mm

Index: webrtc/modules/audio_device/ios/voice_processing_audio_unit.mm
diff --git a/webrtc/modules/audio_device/ios/voice_processing_audio_unit.mm b/webrtc/modules/audio_device/ios/voice_processing_audio_unit.mm
index 08816a41521b84ddc3dfe333caf683c0ff59d8b2..11e5820455c2d50343b70c9d8a7e83264a6ca249 100644
--- a/webrtc/modules/audio_device/ios/voice_processing_audio_unit.mm
+++ b/webrtc/modules/audio_device/ios/voice_processing_audio_unit.mm
@@ -175,7 +175,7 @@ VoiceProcessingAudioUnit::State VoiceProcessingAudioUnit::GetState() const {
 
 bool VoiceProcessingAudioUnit::Initialize(Float64 sample_rate) {
   RTC_DCHECK_GE(state_, kUninitialized);
-  RTCLog(@"Initializing audio unit.");
+  RTCLog(@"Initializing audio unit with sample rate: %f", sample_rate);
 
   OSStatus result = noErr;
   AudioStreamBasicDescription format = GetFormat(sample_rate);
@@ -228,7 +228,9 @@ bool VoiceProcessingAudioUnit::Initialize(Float64 sample_rate) {
     [NSThread sleepForTimeInterval:0.1f];
     result = AudioUnitInitialize(vpio_unit_);
   }
-  RTCLog(@"Voice Processing I/O unit is now initialized.");
+  if (result == noErr) {
+    RTCLog(@"Voice Processing I/O unit is now initialized.");
+  }
   state_ = kInitialized;
   return true;
 }
@@ -237,10 +239,20 @@ bool VoiceProcessingAudioUnit::Start() {
   RTC_DCHECK_GE(state_, kUninitialized);
   RTCLog(@"Starting audio unit.");
 
-  OSStatus result = AudioOutputUnitStart(vpio_unit_);
+  OSStatus result =

[henrika_webrtc, 2016/05/04 12:33:07]

Perhaps a comment regarding why we need this listener.

Apple states "Listen for this property when you do care what the hardware sample
rate is and you want to match your audio processing to the hardware sample rate
(this is the typical case).

The Audio Unit will send you a notification when the hardware sample rate
changes. Your application will need to stop rendering, reconfigure any
processing being done for the new sample rate, then start rendering again. The
sample rate change will be on the Output scope of Bus 0.

Your application should check the rate when called and only do any
reconfiguration when the new rate is different from the current rate. When the
sample rates differ, stop rendering, reconfiguring your audio processing to the
new sample rate and then restart."

[tkchin_webrtc, 2016/05/05 23:23:28]

Removing these changes for now. Will address BT issues separately.

[henrika_webrtc, 2016/05/06 11:22:17]

Acknowledged.

+      AudioUnitAddPropertyListener(vpio_unit_, kAudioUnitProperty_SampleRate,
+                                   OnSampleRateChange, this);
+  if (result != noErr) {
+    RTCLogError(@"Failed to add sample rate listener. Error=%ld.",
+                (long)result);
+  }
+
+  result = AudioOutputUnitStart(vpio_unit_);
   if (result != noErr) {
     RTCLogError(@"Failed to start audio unit. Error=%ld", (long)result);
     return false;
+  } else {
+    RTCLog(@"Started audio unit");
   }
   state_ = kStarted;
   return true;
@@ -254,7 +266,19 @@ bool VoiceProcessingAudioUnit::Stop() {
   if (result != noErr) {
     RTCLogError(@"Failed to stop audio unit. Error=%ld", (long)result);
     return false;
+  } else {
+    RTCLog(@"Stopped audio unit");
+  }
+
+  result =

[henrika_webrtc, 2016/05/04 12:33:07]

Do we need a check that it is disabled at close?

[tkchin_webrtc, 2016/05/05 23:23:28]

Removing these changes for now. Will address BT issues separately.

[henrika_webrtc, 2016/05/06 11:22:16]

Acknowledged.

+      AudioUnitRemovePropertyListenerWithUserData(vpio_unit_,
+                                                  kAudioUnitProperty_SampleRate,
+                                                  OnSampleRateChange, this);
+  if (result != noErr) {
+    RTCLogError(@"Failed to remove sample rate listener. Error=%ld.",
+                (long)result);
   }
+
   state_ = kInitialized;
   return true;
 }
@@ -267,6 +291,8 @@ bool VoiceProcessingAudioUnit::Uninitialize() {
   if (result != noErr) {
     RTCLogError(@"Failed to uninitialize audio unit. Error=%ld", (long)result);
     return false;
+  } else {
+    RTCLog(@"Uninitialized audio unit.");
   }
   return true;
 }
@@ -312,6 +338,17 @@ OSStatus VoiceProcessingAudioUnit::OnDeliverRecordedData(
                                                num_frames, io_data);
 }
 
+void VoiceProcessingAudioUnit::OnSampleRateChange(

[henrika_webrtc, 2016/05/04 12:33:07]

Can we now get this callback and the routing change callback?
Conflicts?

[tkchin_webrtc, 2016/05/05 23:23:28]

There shouldn't be conflicts - we are always using the sample rate from the
audio session.

[henrika_webrtc, 2016/05/06 11:22:17]

Acknowledged.

+    void* in_ref_con,
+    AudioUnit audio_unit,
+    AudioUnitPropertyID property_id,
+    AudioUnitScope scope,
+    AudioUnitElement element) {
+  VoiceProcessingAudioUnit* vp_unit =
+      static_cast<VoiceProcessingAudioUnit*>(in_ref_con);
+  vp_unit->NotifySampleRateChange(audio_unit, property_id, scope, element);
+}
+
 OSStatus VoiceProcessingAudioUnit::NotifyGetPlayoutData(
     AudioUnitRenderActionFlags* flags,
     const AudioTimeStamp* time_stamp,
@@ -332,6 +369,32 @@ OSStatus VoiceProcessingAudioUnit::NotifyDeliverRecordedData(
                                           num_frames, io_data);
 }
 
+void VoiceProcessingAudioUnit::NotifySampleRateChange(
+    AudioUnit audio_unit,
+    AudioUnitPropertyID property_id,
+    AudioUnitScope scope,
+    AudioUnitElement element) {
+  RTC_DCHECK_EQ(audio_unit, vpio_unit_);
+  RTC_DCHECK_EQ(property_id, kAudioUnitProperty_SampleRate);
+  // We only care about the output.

[henrika_webrtc, 2016/05/04 12:33:07]

Have you really been able to trigger callback on other scope/bus?

[tkchin_webrtc, 2016/05/05 23:23:28]

Nope. But just in case.

[henrika_webrtc, 2016/05/06 11:22:17]

Acknowledged.

+  if (scope != kAudioUnitScope_Output || element != kOutputBus) {
+    return;
+  }
+  Float64 sample_rate = 0;
+  UInt32 sample_rate_size = sizeof(Float64);
+  OSStatus status = AudioUnitGetProperty(audio_unit,
+                                         kAudioUnitProperty_SampleRate,
+                                         kAudioUnitScope_Output,
+                                         kOutputBus,
+                                         &sample_rate,
+                                         &sample_rate_size);
+  if (status != noErr) {
+    RTCLogError(@"Failed to get sample rate. Error=%ld.", (long)status);
+    return;
+  }
+  observer_->OnSampleRateChange(sample_rate);
+}
+
 AudioStreamBasicDescription VoiceProcessingAudioUnit::GetFormat(
     Float64 sample_rate) const {
   // Set the application formats for input and output: