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Tengo una aplicación que cuando se carga una vista, comienza a capturar video y audio, y al finalizar, la graba en la carpeta de documentos de la aplicación, junto con el Camera Roll del iPad en el que se está ejecutando. Me aseguré y agregué la entrada a la sesión tanto para audio como para video, pero cuando voy a ver el video guardado, no hay audio. ¿Alguien puede detectar algo en mi código que indique dónde está el problema?

UPDATE: nunca se muestran mensajes de error. Sin embargo, encontré un denominador común. El audio grabará, pero solo si la grabación es de 10 segundos o menos. Si llega a los 11 segundos, el audio no se graba.

NSLog muestra

Finalizado con error: (nulo)

-(void)viewWillAppear:(BOOL)animated {
    NSDate *today = [NSDate date];
    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
    [dateFormatter setDateFormat:@"MMM d hh:mm:ss a"];
    // display in 12HR/24HR (i.e. 11:25PM or 23:25) format according to User Settings
    NSString *currentTime = [dateFormatter stringFromDate:today];
    NSError* error4 = nil;
    AVAudioSession* audioSession = [AVAudioSession sharedInstance];
    [audioSession setCategory:AVAudioSessionCategoryAmbient error:&error4];
    OSStatus propertySetError = 0;
    UInt32 allowMixing = true;
    propertySetError |= AudioSessionSetProperty(kAudioSessionProperty_OtherMixableAudioShouldDuck, sizeof(allowMixing), &allowMixing);

    // Activate the audio session
    error4 = nil;
    if (![audioSession setActive:YES error:&error4]) {
        NSLog(@"AVAudioSession setActive:YES failed: %@", [error4 localizedDescription]);
    }
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectoryPath = [paths objectAtIndex:0];

    session = [[AVCaptureSession alloc] init];
    [session beginConfiguration];
    session.sessionPreset = AVCaptureSessionPresetMedium;
    self.navigationController.navigationBarHidden = YES;

    NSError *error = nil;

    AVCaptureDevice *audioCaptureDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeAudio];
    NSError *error2 = nil;
    AVCaptureDeviceInput *audioInput = [AVCaptureDeviceInput deviceInputWithDevice:audioCaptureDevice error:&error2];


    AVCaptureDevice *device;
    AVCaptureDevicePosition desiredPosition = AVCaptureDevicePositionBack;
    // find the front facing camera

    device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];


    // get the input device
    AVCaptureDeviceInput *deviceInput = [AVCaptureDeviceInput deviceInputWithDevice:device error:&error];




    AVCaptureMovieFileOutput *movieFileOutput = [[AVCaptureMovieFileOutput alloc] init];

    NSString *archives = [documentsDirectoryPath stringByAppendingPathComponent:@"archives"];
    NSString *editedfilename = [[@"ComeOnDown" lastPathComponent] stringByDeletingPathExtension];
    NSString *datestring = [[editedfilename stringByAppendingString:@" "] stringByAppendingString:currentTime];
    NSLog(@"%@", datestring);
    NSString *outputpathofmovie = [[archives stringByAppendingPathComponent:datestring] stringByAppendingString:@".mp4"];
    NSURL *outputURL = [[NSURL alloc] initFileURLWithPath:outputpathofmovie];
    [session addInput:audioInput];
    [session addInput:deviceInput];
    [session addOutput:movieFileOutput];
    [session commitConfiguration];
    [session startRunning];




    AVCaptureVideoPreviewLayer *previewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:session];
    previewLayer.backgroundColor = [[UIColor blackColor] CGColor];
    previewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;
    previewLayer.connection.videoOrientation = AVCaptureVideoOrientationLandscapeRight;

     CALayer *rootLayer = [vImagePreview layer];
    [rootLayer setMasksToBounds:YES];
    [previewLayer setFrame:[rootLayer bounds]];
    [rootLayer addSublayer:previewLayer];

    [movieFileOutput startRecordingToOutputFileURL:outputURL recordingDelegate:self];



    //session = nil;
    if (error) {
        UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:
                                  [NSString stringWithFormat:@"Failed with error %d", (int)[error code]]
                                                            message:[error localizedDescription]
                                                           delegate:nil
                                                  cancelButtonTitle:@"Dismiss"
                                                  otherButtonTitles:nil];
        [alertView show];

    }
    [super viewWillAppear:YES];

}

-(void)captureOutput:(AVCaptureFileOutput *)captureOutput didStartRecordingToOutputFileAtURL:(NSURL *)fileURL fromConnections:(NSArray *)connections {

}
-(void)video:(NSString *)videoPath didFinishSavingWithError:(NSError *)error contextInfo:(void *)contextInfo{
    NSLog(@"Finished with error: %@", error);
}
- (void)captureOutput:(AVCaptureFileOutput *)captureOutput didFinishRecordingToOutputFileAtURL:(NSURL *)outputFileURL fromConnections:(NSArray *)connections error:(NSError *)error {
    //finished
    NSLog(@"Finished");
    NSString *proud = [[NSString alloc] initWithString:[outputFileURL path]];
    UISaveVideoAtPathToSavedPhotosAlbum(proud, self, @selector(video:didFinishSavingWithError: contextInfo:), (__bridge void *)(proud));
}