AVFoundation Chapter Helpers HBM 4/30/12

pg_241_BNRAVViewController.m

- (void)willAnimateRotationToInterfaceOrientation:(UIInterfaceOrientation)toIO
                                         duration:(NSTimeInterval)duration
{
    CGFloat angle = 0;
    switch (toIO) {
        case UIInterfaceOrientationPortrait:
            angle = 0;
            break;
        case UIInterfaceOrientationPortraitUpsideDown:
            angle = M_PI;
            break;
        case UIInterfaceOrientationLandscapeLeft:
            angle = M_PI_2;
            break;
        case UIInterfaceOrientationLandscapeRight:
            angle = -M_PI_2;
            break;
        default:
            break;
    }
    [previewLayer setAffineTransform:CGAffineTransformMakeRotation(angle)];
}

-(void)didRotateFromInterfaceOrientation:(UIInterfaceOrientation)fromIO
{
    CALayer *rootLayer = [previewView layer];
    [previewLayer setFrame:[rootLayer bounds]];
}

pg_243_BNRAVViewController.m

- (CGAffineTransform)assetWriterVideoInTransform:(UIInterfaceOrientation)io
{
    CGFloat angle = 0;
    switch (io) {
        case UIInterfaceOrientationPortrait:
            angle = M_PI_2;
            break;
        case UIInterfaceOrientationPortraitUpsideDown:
            angle = -M_PI_2;
            break;
        case UIInterfaceOrientationLandscapeLeft:
            angle = M_PI;
            break;
        case UIInterfaceOrientationLandscapeRight:
            angle = 0;
            break;
        default:
            break;
    }
    return CGAffineTransformMakeRotation(angle);
}

- (BOOL) setupAssetWriterVideoInput:(CMFormatDescriptionRef)currentFormatDescription 
{
    float bitsPerPixel;
    CMVideoDimensions dimensions = 
        CMVideoFormatDescriptionGetDimensions(currentFormatDescription);
    int numPixels = dimensions.width * dimensions.height;
    int bitsPerSecond;
    
    // Assume that lower-than-SD resolutions are intended for streaming,
    // and use a lower bitrate
    if (numPixels < (640 * 480))
        bitsPerPixel = 4.05; // quality produced by AVCaptureSessionPresetMedium or Low.
    else
        bitsPerPixel = 11.4; // quality produced by AVCaptureSessionPresetHigh.
    
    bitsPerSecond = numPixels * bitsPerPixel;
    
    NSDictionary *videoCompressionSettings =
        [NSDictionary dictionaryWithObjectsAndKeys:
              AVVideoCodecH264, AVVideoCodecKey,
              [NSNumber numberWithInteger:dimensions.width], AVVideoWidthKey,
              [NSNumber numberWithInteger:dimensions.height], AVVideoHeightKey,
              [NSDictionary dictionaryWithObjectsAndKeys:
                  [NSNumber numberWithInteger:bitsPerSecond],
                      AVVideoAverageBitRateKey,
                  [NSNumber numberWithInteger:30],
                      AVVideoMaxKeyFrameIntervalKey,
               nil], AVVideoCompressionPropertiesKey,
              nil];
      if ([assetWriter canApplyOutputSettings:videoCompressionSettings 
                                 forMediaType:AVMediaTypeVideo]) {
          assetWriterVideoIn = [[AVAssetWriterInput alloc]
                      initWithMediaType:AVMediaTypeVideo
                      outputSettings:videoCompressionSettings];
        assetWriterVideoIn.expectsMediaDataInRealTime = YES;
        assetWriterVideoIn.transform = 
            [self assetWriterVideoInTransform:[self interfaceOrientation]];
        if ([assetWriter canAddInput:assetWriterVideoIn])
            [assetWriter addInput:assetWriterVideoIn];
        else {
            NSLog(@"Couldn't add asset writer video input.");
            return NO;
        }
    }
    else {
        NSLog(@"Couldn't apply video output settings.");
        return NO;
    }
    
    return YES;
}

pg_245_BNRAVViewController.m

- (void)removeMovieFile
{
    // remove the file if it already exists
    NSFileManager *fileManager = [NSFileManager defaultManager];
    NSString *filePath = [movieURL path];
    if ([fileManager fileExistsAtPath:filePath]) {
        NSError *error;
        BOOL success = [fileManager removeItemAtPath:filePath error:&error];
        if (!success)
            NSLog(@"(removeMovieFile) error %@: %@", error.localizedDescription, 
                error.localizedFailureReason);
    }
}