ALAssersLibrary category for getting the video's orientation.

ALAssetsLibrary+VideoOrientation.h

@interface ALAssetsLibrary (VideoOrientation)

+ (UIInterfaceOrientation)orientationForTrack:(AVAsset *)asset;

@end

ALAssetsLibrary+VideoOrientation.m

#import "ALAssetsLibrary+VideoOrientation.h"

@implementation ALAssetsLibrary (VideoOrientation)

+ (UIInterfaceOrientation)orientationForTrack:(AVAsset *)asset
{
    NSArray *videoAssets = [asset tracksWithMediaType:AVMediaTypeVideo];
    
    if (!videoAssets.count)
    {
        NSLog(@"No video assets found.");
        return UIInterfaceOrientationPortrait;
    }
    
    // Get the video track.
    AVAssetTrack *videoTrack = [videoAssets objectAtIndex:0];
    
    CGSize size = [videoTrack naturalSize];
    CGAffineTransform preferredTransform = [videoTrack preferredTransform];
    
    // Return interface orientation based on
    // the preferred transform and size of the video.
    if (size.width == preferredTransform.tx &&
        size.height == preferredTransform.ty)
    {
        return UIInterfaceOrientationLandscapeRight;
    }
    else if (preferredTransform.tx == 0 &&
             preferredTransform.ty == 0)
    {
        return UIInterfaceOrientationLandscapeLeft;
    }
    else if (preferredTransform.tx == 0 &&
             preferredTransform.ty == size.width)
    {
        return UIInterfaceOrientationPortraitUpsideDown;
    }
    else
    {
        return UIInterfaceOrientationPortrait;
    }
}

@end