iphone - Using AVCaptureSession and AVAudioPlayer together

Question

I am able to record video and output the movie to a file correctly. However, I have a problem with video recording (no video ouput) when trying to use AVAudioPlayer to play some audio. Does it mean that I cannot use AVCaptureSession and AVAudioPlayer at the same time? Here is my code to create the capture session and to play the audio. The video capture is started first, then during the capturing, I want to play some audio. Thanks so much for any help.

Code to create the capture session to record video (with audio) - output to a .mov file:

- (void)addVideoInput
    AVCaptureDevice *audioDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeAudio];
    //... also some code for setting up videoDevice/frontCamera
    NSError *error;
    AVCaptureDeviceInput *videoIn = [AVCaptureDeviceInput 
    deviceInputWithDevice:frontCamera error:&error];
    AVCaptureDeviceInput *audioIn = [AVCaptureDeviceInput 
    deviceInputWithDevice:audioDevice error:&error];
    if (!error) {
         if ([captureSession canAddInput:audioIn])
              [captureSession addInput:audioIn];
         else
              NSLog(@"Couldn't add audio input.");  
         if ([captureSession canAddInput:videoIn])
              [captureSession addInput:videoIn];
         else
              NSLog(@"Couldn't add video input.");
}
- (void)addVideoOutput
{
     AVCaptureMovieFileOutput *m_captureFileOutput = [[AVCaptureMovieFileOutput alloc] init];
     [captureSession addOutput:m_captureFileOutput];

     [captureSession startRunning];

     NSString *docDir = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
     NSMutableString *filePath = [NSMutableString stringWithString:@"Movie.mov"];
     NSString* fileRoot = [docDir stringByAppendingPathComponent:filePath];
     NSURL *fileURL = [NSURL fileURLWithPath:fileRoot];

     AVCaptureConnection *videoConnection = NULL;

     for ( AVCaptureConnection *connection in [m_captureFileOutput connections] ) 
     {
         for ( AVCaptureInputPort *port in [connection inputPorts] ) 
         {
             if ( [[port mediaType] isEqual:AVMediaTypeVideo] ) 
             {
                 videoConnection = connection;

             }
         }
     }

     [videoConnection setVideoOrientation:AVCaptureVideoOrientationLandscapeRight]; 


     [m_captureFileOutput startRecordingToOutputFileURL:fileURL recordingDelegate:self];
     [m_captureFileOutput release];
}

Code to play the audio, this function is call during the video capture session. If I don't call this function, the video is recorded and I am able to save to the .mov file. However, if I call this function, there's no output .mov file.

- (void)playAudio
{
     NSString *soundFilePath = [[NSBundle mainBundle] pathForResource:@"AudioFile" ofType:@"mp3"];
     NSURL *fileURL = [[NSURL alloc] initFileURLWithPath:soundFilePath];
     AVAudioPlayer *newPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:fileURL error:nil];
     [fileURL release];
     self.audioPlayer = newPlayer;
     [newPlayer release];
     [audioPlayer setDelegate:self];
     [audioPlayer prepareToPlay];
     [audioPlayer play];
}

Answer 1

I fixed the problem by setting up the audio session. I called the following function before creating the audio player object to play the audio. That way, I was able to record video (with audio) and play audio at the same time.

- (void)setupAudioSession {

        static BOOL audioSessionSetup = NO;
        if (audioSessionSetup) {
                return;   
        }
        [[AVAudioSession sharedInstance] setCategory: AVAudioSessionCategoryPlayback error: nil];
        UInt32 doSetProperty = 1;

        AudioSessionSetProperty (kAudioSessionProperty_OverrideCategoryMixWithOthers, sizeof(doSetProperty), &doSetProperty);

        [[AVAudioSession sharedInstance] setActive: YES error: nil];

         audioSessionSetup = YES;

}


- (void)playAudio
{
         [self setupAudioSession];
         NSString *soundFilePath = [[NSBundle mainBundle] pathForResource:@"AudioFile" ofType:@"mp3"];
         NSURL *fileURL = [[NSURL alloc] initFileURLWithPath:soundFilePath];
         AVAudioPlayer *newPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:fileURL error:nil];
         [fileURL release];
         self.audioPlayer = newPlayer;
         [newPlayer release];
         [audioPlayer setDelegate:self];
         [audioPlayer prepareToPlay];
         [audioPlayer play];
    }