Add a watermark image to a video - ios

Question

I'm new to AVFoundation, and i'm trying to add a image to a video. however i keep getting an error : failed Optional(Error Domain=AVFoundationErrorDomain Code=-11823 "Cannot Save" UserInfo={NSLocalizedDescription=Cannot Save, NSLocalizedRecoverySuggestion=Try saving again.})
. What am i doing wrong. Here is my code:
func createVideo() {
let documentsPath = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true)[0] as NSString
let fileURL = NSURL(fileURLWithPath: "\(documentsPath)/\(self.randomVideoFileName).mov")
let composition = AVMutableComposition()
let vidAsset = AVURLAsset(URL: fileURL, options: nil)
// get video track
let vtrack = vidAsset.tracksWithMediaType(AVMediaTypeVideo)
let videoTrack:AVAssetTrack = vtrack[0]
let vid_timerange = CMTimeRangeMake(kCMTimeZero, vidAsset.duration)
do {
let compositionvideoTrack:AVMutableCompositionTrack = composition.addMutableTrackWithMediaType(AVMediaTypeVideo, preferredTrackID: CMPersistentTrackID())
try compositionvideoTrack.insertTimeRange(vid_timerange, ofTrack: videoTrack, atTime: kCMTimeZero)
compositionvideoTrack.preferredTransform = videoTrack.preferredTransform
} catch {
print(error)
}
//Get the video
let fullSizeImage = videoTrack
let newOverLayHeight = fullSizeImage.naturalSize.width / self.containerView!.frame.width * self.containerView!.frame.height
UIGraphicsBeginImageContext(CGSizeMake(fullSizeImage.naturalSize.width, newOverLayHeight));
self.containerView!.drawViewHierarchyInRect(CGRectMake(0, 0, fullSizeImage.naturalSize.width, newOverLayHeight), afterScreenUpdates: true)
let overlayImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
let imglogo = UIImage(named: "image.png")
let imglayer = CALayer()
imglayer.contents = imglogo?.CGImage
imglayer.frame = CGRectMake(0,fullSizeImage.naturalSize.height - newOverLayHeight, overlayImage.size.width, overlayImage.size.height)
let videolayer = CALayer()
videolayer.frame = CGRectMake(0, 0, fullSizeImage.naturalSize.width, fullSizeImage.naturalSize.height)
let parentlayer = CALayer()
parentlayer.frame = CGRectMake(0, 0, fullSizeImage.naturalSize.width, fullSizeImage.naturalSize.height)
parentlayer.addSublayer(imglayer)
let layercomposition = AVMutableVideoComposition()
layercomposition.frameDuration = CMTimeMake(1, 30)
layercomposition.renderSize = fullSizeImage.naturalSize
layercomposition.animationTool = AVVideoCompositionCoreAnimationTool(postProcessingAsVideoLayer: videolayer, inLayer: parentlayer)
let instruction = AVMutableVideoCompositionInstruction()
instruction.timeRange = CMTimeRangeMake(kCMTimeZero, composition.duration)
let videotrack = composition.tracksWithMediaType(AVMediaTypeVideo)[0] as AVAssetTrack
let layerinstruction = AVMutableVideoCompositionLayerInstruction(assetTrack: videotrack)
instruction.layerInstructions = NSArray(object: layerinstruction) as! [AVVideoCompositionLayerInstruction]
layercomposition.instructions = NSArray(object: instruction) as! [AVVideoCompositionInstructionProtocol]
// create new file to receive data
let docsDir: AnyObject = documentsPath
let movieFilePath = docsDir.stringByAppendingPathComponent("result.mov")
let movieDestinationUrl = NSURL(fileURLWithPath: movieFilePath)
// use AVAssetExportSession to export video
let assetExport = AVAssetExportSession(asset: composition, presetName:AVAssetExportPresetHighestQuality)
assetExport!.outputFileType = AVFileTypeQuickTimeMovie
assetExport!.outputURL = movieDestinationUrl
assetExport!.exportAsynchronouslyWithCompletionHandler({
switch assetExport!.status{
case AVAssetExportSessionStatus.Failed:
print("failed \(assetExport!.error)")
case AVAssetExportSessionStatus.Cancelled:
print("cancelled \(assetExport!.error)")
default:
print("Movie complete")
// save to photoalbum
NSOperationQueue.mainQueue().addOperationWithBlock({ () -> Void in
UISaveVideoAtPathToSavedPhotosAlbum(movieDestinationUrl.absoluteString, self, "image:didFinishSavingWithError:contextInfo:", nil)
})
}
})
}

Answer 1

As Matt commented, you've forgotten to delete the output file (AVFoundation refuses to overwrite files for some reason). So do that:
let movieDestinationUrl = NSURL(fileURLWithPath: movieFilePath)
_ = try? NSFileManager().removeItemAtURL(movieDestinationUrl)
That fixes the error, but you won't yet see your watermark because you're not setting the AVAssetExportSession's videoComposition:
assetExport?.videoComposition = layercomposition // important!
assetExport!.exportAsynchronouslyWithCompletionHandler({...})

Answer 2

Hi i have done this in ObjectivC following is my code...
AVMutableVideoComposition* videoComp = [AVMutableVideoComposition videoComposition] ;
CGSize videoSize = CGSizeApplyAffineTransform(a_compositionVideoTrack.naturalSize, a_compositionVideoTrack.preferredTransform);
CATextLayer *titleLayer = [CATextLayer layer];
titleLayer.string = #"lippieapp.com";
titleLayer.font = (__bridge CFTypeRef)(#"Helvetica-Bold");
titleLayer.fontSize = 32.0;
//titleLayer.alignmentMode = kCAAlignmentCenter;
titleLayer.frame = CGRectMake(30, 0, 250, 60); //You may need to adjust this for proper display
CALayer *parentLayer = [CALayer layer];
CALayer *videoLayer = [CALayer layer];
parentLayer.frame = CGRectMake(0, 0, videoSize.width, videoSize.height);
videoLayer.frame = CGRectMake(0, 0, videoSize.width, videoSize.height);
[parentLayer addSublayer:videoLayer];