Surface audio unit errors.

With this change, we catch audio unit start errors and pipe them to the
audio session. The audio session notifies its delegate, which can then
take appropriate action based on the error code.
The signal follows the same path as the playout glitch detection.

Bug: webrtc:13119
Change-Id: I8c9f9d2a1e3457447d0ce61ad197f7e1c6392837
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/230240
Commit-Queue: Peter Hanspers <peterhanspers@webrtc.org>
Reviewed-by: Henrik Andreassson <henrika@webrtc.org>
Reviewed-by: Xavier Lepaul‎ <xalep@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#34862}

sdk/objc/components/audio/RTCAudioSession+Private.h

@@ -73,6 +73,12 @@ NS_ASSUME_NONNULL_BEGIN
 /** Returns a configuration error with the given description. */
 - (NSError *)configurationErrorWithDescription:(NSString *)description;
 
+/** Notifies the reciever that a playout glitch was detected. */
+- (void)notifyDidDetectPlayoutGlitch:(int64_t)totalNumberOfGlitches;
+
+/** Notifies the reciever that there was an error when starting an audio unit. */
+- (void)notifyAudioUnitStartFailedWithError:(OSStatus)error;
+
 // Properties and methods for tests.
 - (void)notifyDidBeginInterruption;
 - (void)notifyDidEndInterruptionWithShouldResumeSession:(BOOL)shouldResumeSession;
@@ -83,7 +89,6 @@ NS_ASSUME_NONNULL_BEGIN
 - (void)notifyDidChangeCanPlayOrRecord:(BOOL)canPlayOrRecord;
 - (void)notifyDidStartPlayOrRecord;
 - (void)notifyDidStopPlayOrRecord;
-- (void)notifyDidDetectPlayoutGlitch:(int64_t)totalNumberOfGlitches;
 
 @end
 

sdk/objc/components/audio/RTCAudioSession.h

@@ -99,6 +99,9 @@ RTC_OBJC_EXPORT
     failedToSetActive:(BOOL)active
                 error:(NSError *)error;
 
+- (void)audioSession:(RTC_OBJC_TYPE(RTCAudioSession) *)audioSession
+    audioUnitStartFailedWithError:(NSError *)error;
+
 @end
 
 /** This is a protocol used to inform RTCAudioSession when the audio session

sdk/objc/components/audio/RTCAudioSession.mm

@@ -794,6 +794,18 @@ NSString * const kRTCAudioSessionOutputVolumeSelector = @"outputVolume";
   }
 }
 
+- (void)notifyAudioUnitStartFailedWithError:(OSStatus)error {
+  for (auto delegate : self.delegates) {
+    SEL sel = @selector(audioSession:audioUnitStartFailedWithError:);
+    if ([delegate respondsToSelector:sel]) {
+      [delegate audioSession:self
+          audioUnitStartFailedWithError:[NSError errorWithDomain:kRTCAudioSessionErrorDomain
+                                                            code:error
+                                                        userInfo:nil]];
+    }
+  }
+}
+
 - (void)notifyDidBeginInterruption {
   for (auto delegate : self.delegates) {
     SEL sel = @selector(audioSessionDidBeginInterruption:);

sdk/objc/native/src/audio/audio_device_ios.mm

@@ -235,8 +235,11 @@ int32_t AudioDeviceIOS::StartPlayout() {
     fine_audio_buffer_->ResetPlayout();
   }
   if (!recording_ && audio_unit_->GetState() == VoiceProcessingAudioUnit::kInitialized) {
-    if (!audio_unit_->Start()) {
-      RTCLogError(@"StartPlayout failed to start audio unit.");
+    OSStatus result = audio_unit_->Start();
+    if (result != noErr) {
+      RTC_OBJC_TYPE(RTCAudioSession)* session = [RTC_OBJC_TYPE(RTCAudioSession) sharedInstance];
+      [session notifyAudioUnitStartFailedWithError:result];
+      RTCLogError(@"StartPlayout failed to start audio unit, reason %d", result);
       return -1;
     }
     RTC_LOG(LS_INFO) << "Voice-Processing I/O audio unit is now started";
@@ -288,8 +291,11 @@ int32_t AudioDeviceIOS::StartRecording() {
     fine_audio_buffer_->ResetRecord();
   }
   if (!playing_ && audio_unit_->GetState() == VoiceProcessingAudioUnit::kInitialized) {
-    if (!audio_unit_->Start()) {
-      RTCLogError(@"StartRecording failed to start audio unit.");
+    OSStatus result = audio_unit_->Start();
+    if (result != noErr) {
+      RTC_OBJC_TYPE(RTCAudioSession)* session = [RTC_OBJC_TYPE(RTCAudioSession) sharedInstance];
+      [session notifyAudioUnitStartFailedWithError:result];
+      RTCLogError(@"StartRecording failed to start audio unit, reason %d", result);
       return -1;
     }
     RTC_LOG(LS_INFO) << "Voice-Processing I/O audio unit is now started";
@@ -620,9 +626,16 @@ void AudioDeviceIOS::HandleSampleRateChange(float sample_rate) {
   }
 
   // Restart the audio unit if it was already running.
-  if (restart_audio_unit && !audio_unit_->Start()) {
-    RTCLogError(@"Failed to start audio unit with sample rate: %f", session_sample_rate);
-    return;
+  if (restart_audio_unit) {
+    OSStatus result = audio_unit_->Start();
+    if (result != noErr) {
+      RTC_OBJC_TYPE(RTCAudioSession)* session = [RTC_OBJC_TYPE(RTCAudioSession) sharedInstance];
+      [session notifyAudioUnitStartFailedWithError:result];
+      RTCLogError(@"Failed to start audio unit with sample rate: %f, reason %d",
+                  session_sample_rate,
+                  result);
+      return;
+    }
   }
   RTCLog(@"Successfully handled sample rate change.");
 }
@@ -801,8 +814,10 @@ void AudioDeviceIOS::UpdateAudioUnit(bool can_play_or_record) {
     // Log session settings before trying to start audio streaming.
     RTC_OBJC_TYPE(RTCAudioSession)* session = [RTC_OBJC_TYPE(RTCAudioSession) sharedInstance];
     RTCLog(@"%@", session);
-    if (!audio_unit_->Start()) {
-      RTCLogError(@"Failed to start audio unit.");
+    OSStatus result = audio_unit_->Start();
+    if (result != noErr) {
+      [session notifyAudioUnitStartFailedWithError:result];
+      RTCLogError(@"Failed to start audio unit, reason %d", result);
       return;
     }
   }

sdk/objc/native/src/audio/voice_processing_audio_unit.h

@@ -78,7 +78,7 @@ class VoiceProcessingAudioUnit {
   bool Initialize(Float64 sample_rate);
 
   // Starts the underlying audio unit.
-  bool Start();
+  OSStatus Start();
 
   // Stops the underlying audio unit.
   bool Stop();

sdk/objc/native/src/audio/voice_processing_audio_unit.mm

@@ -332,19 +332,19 @@ bool VoiceProcessingAudioUnit::Initialize(Float64 sample_rate) {
   return true;
 }
 
-bool VoiceProcessingAudioUnit::Start() {
+OSStatus 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;
+    return result;
   } else {
     RTCLog(@"Started audio unit");
   }
   state_ = kStarted;
-  return true;
+  return noErr;
 }
 
 bool VoiceProcessingAudioUnit::Stop() {