iOS Rotating Video Using AVMutableVideoCompositionLayerInstruction - objective-c

Question

At the moment, whenever I export a video it appears to be rotated 90 degrees to the right, but I am not sure why. My current code is:
AVURLAsset *videoAsset = [[AVURLAsset alloc] initWithURL:self.video options:nil];
AVMutableComposition *mixComposition = [AVMutableComposition composition];
AVMutableCompositionTrack *compositionVideoTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
AVAssetTrack *clipVideoTrack = [[videoAsset tracksWithMediaType:AVMediaTypeVideo] lastObject];
[compositionVideoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, videoAsset.duration)
ofTrack:clipVideoTrack
atTime:kCMTimeZero
error:nil];
[compositionVideoTrack setPreferredTransform:[[[videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] preferredTransform]];
CGSize videoSize = [clipVideoTrack naturalSize];
CALayer *parentLayer = [CALayer layer];
CALayer *videoLayer = [CALayer layer];
videoLayer.frame = CGRectMake(0, 0, videoSize.width, videoSize.height);
parentLayer.frame = CGRectMake(0, 0, videoSize.width, videoSize.height);
[parentLayer addSublayer:videoLayer];
AVMutableVideoComposition* videoComp = [AVMutableVideoComposition videoComposition];
videoComp.renderSize = [clipVideoTrack naturalSize];
videoComp.frameDuration = CMTimeMake(1, 30);
videoComp.animationTool = [AVVideoCompositionCoreAnimationTool videoCompositionCoreAnimationToolWithPostProcessingAsVideoLayer:videoLayer inLayer:parentLayer];
AVMutableVideoCompositionInstruction *instruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
instruction.timeRange = CMTimeRangeMake(kCMTimeZero, mixComposition.duration);
AVAssetTrack *videoTrack = [[mixComposition tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];
AVMutableVideoCompositionLayerInstruction *layerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:videoTrack];
instruction.layerInstructions = [NSArray arrayWithObject:layerInstruction];
videoComp.instructions = [NSArray arrayWithObject:instruction];
AVAssetExportSession *assetExport = [[AVAssetExportSession alloc] initWithAsset:mixComposition presetName:AVAssetExportPresetMediumQuality];
assetExport.videoComposition = videoComp;
NSString *videoName = #"output.mov";
NSString *exportPath = [NSTemporaryDirectory() stringByAppendingString:videoName];
NSURL *exportURL = [NSURL fileURLWithPath:exportPath];
if ([[NSFileManager defaultManager] fileExistsAtPath:exportPath])
[[NSFileManager defaultManager] removeItemAtPath:exportPath error:nil];
assetExport.outputFileType = AVFileTypeQuickTimeMovie;
assetExport.outputURL = exportURL;
assetExport.shouldOptimizeForNetworkUse = YES;
[assetExport exportAsynchronouslyWithCompletionHandler:^(void){
dispatch_async(dispatch_get_main_queue(), ^{
[self exportDidFinish:assetExport];
});
}];
I tried using the following code to transform it, and even though it technically does rotate the video, it shrinks the video into a square, and I dont know how to enlarge it to fit the entire screen:
CGAffineTransform rotation = CGAffineTransformMakeRotation(M_PI / 2);
CGAffineTransform translateToCenter = CGAffineTransformMakeTranslation(1000, 1000);
CGAffineTransform mixedTransform = CGAffineTransformConcat(rotation, translateToCenter);
[layerInstruction setTransform:mixedTransform atTime:kCMTimeZero];
Any advice?