Audio Unit - Messing up recording - ios

Question

Sorry for a long introduction of the problem.
In my app I am using recording audio and set category to record
AVAudioSession *session = [AVAudioSession sharedInstance];
[session setCategory:AVAudioSessionCategoryRecord error:&err];
When an ad network shows interstitial ad, after that recording is all mute (there is no sound in recording). As this happens with users on live network only, I am not able to reproduce it at my end.
In the log I get ">>>> frameSizeChanged = 4096" from users which points to webkit code
https://github.com/WebKit/webkit/blob/master/Source/WebCore/platform/audio/ios/AudioDestinationIOS.cpp
This looks like some process is holding on to Audio Unit setup and not letting it go even after it is completed(freed / released).
Question: Is there a way to clean up audio unit setup by some other module? Just need to reset so that recording can work again in app after the ad is shown.
I have tried to capture "AVAudioSessionInterruptionNotification" but there is none. Any help is really appreciated

Answer 1

You need to handle your audio system getting interrupted. Many things can cause your audio to get interrupted:
- Receive a phone call while your app runs
- Other app running uses audio
- iOS needs to play a sound
- etc
Your app needs to detect this interruption as your app's audio session will be essentially muted. Once the interruption is done, you need to restart your session.
Set up your listener as the first step in your session setup
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(yourInterruptionListener:) name:AVAudioSessionInterruptionNotification object:nil];
In your interruption listener, handle the cases of getting interrupted and handle restarting your session
-(void) yourInterruptionListener:(NSNotification*) aNotification
{
NSLog(#"Interruption happened");
NSDictionary *interruptionDict = aNotification.userInfo;
NSNumber* interruptionTypeValue = [interruptionDict valueForKey:AVAudioSessionInterruptionTypeKey];
NSUInteger interruptionType = [interruptionTypeValue intValue];
if ( interruptionType == AVAudioSessionInterruptionTypeBegan)
{
// stop your audio session here
AVAudioSession *session = [AVAudioSession sharedInstance];
NSError *errorInAudio = nil;
[session setActive:NO error:&errorInAudio];
}
else if ( interruptionType == AVAudioSessionInterruptionTypeEnded )
{
// Your interruption ended, restart the session
// call or paste your session startup code here
}
else if ( interruptionType == AVAudioSessionInterruptionOptionShouldResume )
{
}
else
{
NSLog(#"Some other interruption");
}
}
If you need to simulate the behavior of your users, start your app then call your self from a different phone. It will definitely interrupt your audio.