Find the video orientation of an AVAsset. (Useful if you need to send the video to a remote server)

AVAsset+VideoOrientation.h

//
//  AVAsset+VideoOrientation.h
//
//  Created by Luca Bernardi on 19/09/12.
//  Copyright (c) 2012 Luca Bernardi. All rights reserved.
//
#import <AVFoundation/AVFoundation.h>

typedef enum {
  LBVideoOrientationUp,               //Device starts recording in Portrait
	LBVideoOrientationDown,             //Device starts recording in Portrait upside down
	LBVideoOrientationLeft,             //Device Landscape Left  (home button on the left side)
	LBVideoOrientationRight,            //Device Landscape Right (home button on the Right side)
    LBVideoOrientationNotFound = 99     //An Error occurred or AVAsset doesn't contains video track
} LBVideoOrientation;

@interface AVAsset (VideoOrientation)

/**
 Returns a LBVideoOrientation that is the orientation 
 of the iPhone / iPad whent starst recording
 
 @return A LBVideoOrientation that is the orientation of the video
 */
@property (nonatomic, readonly) LBVideoOrientation videoOrientation;

@end

AVAsset+VideoOrientation.mm

//
//  AVAsset+VideoOrientation.m
//
//  Created by Luca Bernardi on 19/09/12.
//  Copyright (c) 2012 Luca Bernardi. All rights reserved.
//

#import "AVAsset+VideoOrientation.h"


static inline CGFloat RadiansToDegrees(CGFloat radians) {
  return radians * 180 / M_PI;
};

@implementation AVAsset (VideoOrientation)
@dynamic videoOrientation;

- (LBVideoOrientation)videoOrientation
{
    NSArray *videoTracks = [self tracksWithMediaType:AVMediaTypeVideo];
    if ([videoTracks count] == 0) {
        return LBVideoOrientationNotFound;
    }
    
    AVAssetTrack* videoTrack    = [videoTracks objectAtIndex:0];
  CGAffineTransform txf       = [videoTrack preferredTransform];
    CGFloat videoAngleInDegree  = RadiansToDegrees(atan2(txf.b, txf.a));

	LBVideoOrientation orientation = 0;
	switch ((int)videoAngleInDegree) {
		case 0:
			orientation = LBVideoOrientationRight;
			break;
		case 90:
			orientation = LBVideoOrientationUp;
			break;
		case 180:
			orientation = LBVideoOrientationLeft;
			break;
		case -90:
			orientation	= LBVideoOrientationDown;
			break;
        default:
            orientation = LBVideoOrientationNotFound;
            break;
	}
	
	return orientation;
}

@end

There must be some bugs if the video is from screen recording.