Provide isAudioEnabled flag to control audio unit.

webrtc/modules/audio_device/ios/voice_processing_audio_unit.mm

 /*
  *  Copyright 2016 The WebRTC Project Authors. All rights reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 157 matching lines @@
   state_ = kUninitialized;
   return true;
 }
 
 VoiceProcessingAudioUnit::State VoiceProcessingAudioUnit::GetState() const {
   return state_;
 }
 
 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);
   UInt32 size = sizeof(format);
 #if !defined(NDEBUG)
   LogStreamDescription(format);
 #endif
 
   // Set the format on the output scope of the input element/bus.
   result =
@@ skipping 32 matching lines @@
     ++failed_initalize_attempts;
     if (failed_initalize_attempts == kMaxNumberOfAudioUnitInitializeAttempts) {
       // Max number of initialization attempts exceeded, hence abort.
       RTCLogError(@"Too many initialization attempts.");
       return false;
     }
     RTCLog(@"Pause 100ms and try audio unit initialization again...");
     [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;
 }
 
 bool VoiceProcessingAudioUnit::Start() {
   RTC_DCHECK_GE(state_, kUninitialized);
   RTCLog(@"Starting audio unit.");
 
   OSStatus 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;
 }
 
 bool VoiceProcessingAudioUnit::Stop() {
   RTC_DCHECK_GE(state_, kUninitialized);
   RTCLog(@"Stopping audio unit.");
 
   OSStatus result = AudioOutputUnitStop(vpio_unit_);
   if (result != noErr) {
     RTCLogError(@"Failed to stop audio unit. Error=%ld", (long)result);
     return false;
+  } else {
+    RTCLog(@"Stopped audio unit");
   }
+
   state_ = kInitialized;
   return true;
 }
 
 bool VoiceProcessingAudioUnit::Uninitialize() {
   RTC_DCHECK_GE(state_, kUninitialized);
   RTCLog(@"Unintializing audio unit.");
 
   OSStatus result = AudioUnitUninitialize(vpio_unit_);
   if (result != noErr) {
     RTCLogError(@"Failed to uninitialize audio unit. Error=%ld", (long)result);
     return false;
+  } else {
+    RTCLog(@"Uninitialized audio unit.");
   }
+
+  state_ = kUninitialized;
   return true;
 }
 
 OSStatus VoiceProcessingAudioUnit::Render(AudioUnitRenderActionFlags* flags,
                                           const AudioTimeStamp* time_stamp,
                                           UInt32 output_bus_number,
                                           UInt32 num_frames,
                                           AudioBufferList* io_data) {
   RTC_DCHECK(vpio_unit_) << "Init() not called.";
 
@@ skipping 89 matching lines @@
     OSStatus result = AudioComponentInstanceDispose(vpio_unit_);
     if (result != noErr) {
       RTCLogError(@"AudioComponentInstanceDispose failed. Error=%ld.",
                   (long)result);
     }
     vpio_unit_ = nullptr;
   }
 }
 
 }  // namespace webrtc