Record Audio/Video with AVCaptureSession and Playback Audio simultaneously?

Question

I'm trying to create an iOS app which can record audio and video while simultaneously outputting audio to the speakers.

To do the recording and preview, I'm using AVCaptureSession, an AVCaptureConnection each for both video and audio, and an AVAssetWriterInput each for both video and audio. I basically achieved this by following the RosyWriter example code.

Prior to setting up recording in this fashion, I was using AVAudioPlayer to play audio.

Now, if I am in the middle of capturing (not even recording, just capturing for preview), and attempt to use AVAudioPlayer, my captureOutput callbacks on my AVCaptureAudioDataOutputSampleBufferDelegate class stop getting called.

Is there a workaround for this?

Is there another, lower level service I should use to be playing audio that won't stop my capture?

mc.

Answer 1

You first set the AVAudioSession and its category. For example in viewDidLoad method,

AVAudioSession *session = [AVAudioSession sharedInstance];
[session setCategory:AVAudioSessionCategoryPlayAndRecord  withOptions:AVAudioSessionCategoryOptionMixWithOthers|AVAudioSessionCategoryOptionDefaultToSpeaker error:nil];

Therefore you can play BGM

    self.player = [[AVAudioPlayer alloc] initWithContentsOfURL:music_url error:nil];
    [self.player setDelegate:self];
    [self.player play];

and record the movie

    self.captureSession = [[AVCaptureSession alloc] init];
    /* ... addInput AVCaptureDeviceInput AVMediaTypeVideo & AVMediaTypeAudio */
    /* ... addOutput */
    [self.captureSession startRunning];
    AVCaptureMovieFileOutput *m_captureFileOutput =[self.captureSession.outputs objectAtIndex:0];
    [m_captureFileOutput startRecordingToOutputFileURL:saveMovieURL recordingDelegate:self];