Audio will make AVCaptureSession terminate

Question

I wrote a app to record video from iPhone. It work fine but have one big problem. When AVCaptureSession start running and user try to play audio from thier library(iPod). This action will make AVCaptureSession terminate. Have any idea can prevent user try to play audio or solve this problem?

---

this is my code:

videoDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];           
audioDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeAudio];

AVCaptureDeviceInput *videoDeviceInput = [[AVCaptureDeviceInput alloc] initWithDevice:videoDevice error:nil];
AVCaptureDeviceInput *audioDeviceInput = [[AVCaptureDeviceInput alloc] initWithDevice:audioDevice error:nil];

movieFileOutput = [[AVCaptureMovieFileOutput alloc] init];

captureSession = [[AVCaptureSession alloc] init];

[captureSession beginConfiguration];
[captureSession setSessionPreset:AVCaptureSessionPresetHigh];
[captureSession addInput:videoDeviceInput];
[captureSession addInput:audioDeviceInput];
[captureSession addOutput:movieFileOutput];
[captureSession commitConfiguration];

[captureSession startRunning];

Answer 1

This worked for me:

- (void)setupAudio {
    [[AVAudioSession sharedInstance] setCategory: AVAudioSessionCategoryPlayback error: nil];
    UInt32 doSetProperty = 1;
    AudioSessionSetProperty (kAudioSessionProperty_OverrideCategoryMixWithOthers, sizeof(doSetProperty), &doSetProperty);
    [[AVAudioSession sharedInstance] setActive: YES error: nil];

}

Answer 2

You need to use the NSNotificationCenter. Use the code below (I also included some other useful methods), and write a method for AVCaptureSessionWasInterruptedNotification that will handle the capture interruption, by any means. I hope that helps.

NSNotificationCenter *notify = [NSNotificationCenter defaultCenter];
[notify addObserver: self selector: @selector(onVideoError:) name: AVCaptureSessionRuntimeErrorNotification object: captureSession];
[notify addObserver: self selector: @selector(onVideoInterrupted:) name: AVCaptureSessionWasInterruptedNotification object: captureSession];
[notify addObserver: self selector: @selector(onVideoEnded:) name: AVCaptureSessionInterruptionEndedNotification object: captureSession];
[notify addObserver: self selector: @selector(onVideoDidStopRunning:) name: AVCaptureSessionDidStopRunningNotification object: captureSession];
[notify addObserver: self selector: @selector(onVideoStart:) name: AVCaptureSessionDidStartRunningNotification object: captureSession];

Answer 3

Try messing with the audio session!

Here's a quick guess about what you could do, but I haven't tried this with the iPod specifically:

OSStatus status = noErr;
status |= AudioSessionInitialize(CFRunLoopGetMain(), kCFRunLoopCommonModes, PVAudioSessionInterruptionListener, NULL);

    status |= AudioSessionSetProperty(kAudioSessionProperty_AudioCategory, sizeof(UInt32), &(UInt32){kAudioSessionCategory_PlayAndRecord});

    status |= AudioSessionSetProperty(kAudioSessionProperty_OverrideCategoryMixWithOthers,
                                      sizeof(UInt32),
                                      &(UInt32){true});

    status |= AudioSessionSetProperty(kAudioSessionProperty_OtherMixableAudioShouldDuck,
                                      sizeof(UInt32),
                                      &(UInt32){false});

status |= AudioSessionSetActive(YES);

if (status != noErr) {
    NSLog(@"ERROR: There was an error in setting the audio session");
}

I've also had some luck with the ambient sound audio category (even though it gives an error, it seems to allow playing audio while recording video):

    status |= AudioSessionSetProperty(kAudioSessionProperty_AudioCategory, sizeof(UInt32), &(UInt32){kAudioSessionCategory_AmbientSound});