How to get correct Orientation for videos from PhotoLibrary iOS

Question

I am trying to implement Instagram video cropping feature. For that i need to get correct orientation of the video with which i will layout my MPMoviePlayerController view in correct aspect ratio and user will then be able to pan the video and shown square video will be cropped on action.

I am having problem with getting correct orientation of the video. I am using following code

AVURLAsset *asset = [AVURLAsset URLAssetWithURL:fileUrl options:nil];
NSArray *tracks = [asset tracksWithMediaType:AVMediaTypeVideo];
AVAssetTrack *track = [tracks objectAtIndex:0];
UIInterfaceOrientation orientation =[self orientationForTrack:track];

// method to get orientation
- (UIInterfaceOrientation)orientationForTrack:(AVAssetTrack *)videoTrack
{
    CGSize size = [videoTrack naturalSize];
    CGAffineTransform txf = [videoTrack preferredTransform];

    if (size.width == txf.tx && size.height == txf.ty)
        return UIInterfaceOrientationLandscapeRight;
    else if (txf.tx == 0 && txf.ty == 0)
        return UIInterfaceOrientationLandscapeLeft;
    else if (txf.tx == 0 && txf.ty == size.width)
        return UIInterfaceOrientationPortraitUpsideDown;
    else
        return UIInterfaceOrientationUnknown;
}

Problem which i am having is that some times the videos which are actually in portrait, above piece of code is classifying it as landscape and vice versa. I only need to know two states of video's orientation (Landscape or Portrait). I want exact same orientation value which MPMoviePlayerController is interpreting. My application only supports Portrait orientation. Any help would be highly appreciated.

PS: Above code is working fine for videos which are captured from iphone camera, videos which are downloaded or shared through the whatsapp are causing the problem.

Answer 1

Only way which solved this issue for me is to capture thumbnail image from the video using method:

- (void)requestThumbnailImagesAtTimes:(NSArray *)playbackTimes timeOption:(MPMovieTimeOption)option

and then adding check on the thumbnail image like :

if (singleFrameImage.size.height > singleFrameImage.size.width) {
    // potrait video
} else {
    // landscape video
}

This solution is tested on videos captured from iPhone camera and also on a set (8-10) of videos randomly downloaded from internet.

Answer 2

AVAssetTrack has property preferredTransform. You can use that for finding actual orientation of video.

     AVAssetTrack *videoAssetTrack = [[videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];
UIImageOrientation videoAssetOrientation_  = UIImageOrientationUp;
CGFloat videoAngle  = RadiansToDegrees(atan2(videoAssetOrientation_.b, videoAssetOrientation_.a));


int  orientation = 0;
switch ((int)videoAngle) {
    case 0:
        orientation = UIImageOrientationRight;
        break;
    case 90:
        orientation = UIImageOrientationUp;
        break;
    case 180:
        orientation = UIImageOrientationLeft;
        break;
    case -90:
        orientation = UIImageOrientationDown;
        break;
    default:
        //Not found
        break;
}