AVAsset Saving video in iOS with image overlay ruins video - ios

Question

I'm trying to merge an image overlay and a video into a new video file. This is the code I am using:
- (void)mergeVideoUrl:(NSURL *)videoURL andOverlayImage:(UIImage *)overlayImage
{
NSLog(#"%s", __PRETTY_FUNCTION__);
// Create an AVURLAsset
AVURLAsset* videoAsset = [[AVURLAsset alloc]initWithURL:videoURL options:nil];
AVMutableComposition* mixComposition = [AVMutableComposition composition];
AVMutableCompositionTrack *compositionVideoTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
AVAssetTrack *clipVideoTrack = [[videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];
[compositionVideoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, videoAsset.duration)
ofTrack:clipVideoTrack
atTime:kCMTimeZero
error:nil];
[compositionVideoTrack setPreferredTransform:[[[videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] preferredTransform]];
CGSize videoSize = [clipVideoTrack naturalSize];
// Get our image layer
CALayer *aLayer = [CALayer layer];
aLayer.contents = (id)overlayImage.CGImage;
aLayer.frame = CGRectMake(0, 0, videoSize.width, videoSize.height);
aLayer.opacity = 1.0;
// Sort the layer order
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];
[parentLayer addSublayer:aLayer];
// Create the composition and add the instructions to insert the layer
AVMutableVideoComposition* videoComp = [AVMutableVideoComposition videoComposition];
videoComp.renderSize = videoSize;
videoComp.frameDuration = CMTimeMake(1, 30);
videoComp.animationTool = [AVVideoCompositionCoreAnimationTool videoCompositionCoreAnimationToolWithPostProcessingAsVideoLayer:videoLayer inLayer:parentLayer];
// Instruction
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];
// Export
AVAssetExportSession *assetExport = [[AVAssetExportSession alloc] initWithAsset:mixComposition presetName:AVAssetExportPresetHighestQuality];
assetExport.videoComposition = videoComp;
NSString* videoName = #"mynewwatermarkedvideo.mov";
NSString *exportPath = [NSTemporaryDirectory() stringByAppendingPathComponent: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)
{
//FINALIZATION CODE HERE
NSLog(#"DONE: %#", exportUrl);
}];
}
The problem is that it screws up the video. Any idea why?
I have a feeling the video frame size might have something to do with it or the aspect ratio as if I set a size of (2000,2000), it seems to work ok but with a lot of black edges.
EDIT-----
It seems that if I set CGSize videoSize to a ratio of 2/3 e.g.320x480 or 1280x1920 then it works, however the resulting video has a black bar down the right hand side. Why would [clipVideoTrack naturalSize] report a size of 1080x1920 but it screws up unless I use 1280x1920? I think it might be a transform/crop issue?
EDIT2-----
Changing the AVAssetExportSession presetName between AVAssetExportPresetLowQuality, AVAssetExportPresetMediumQuality & AVAssetExportPresetHighestQuality results in different sized videos. So I think that is overriding the output video frame size somehow.

Answer 1

CGSize videoSize = [clipVideoTrack naturalSize];
This gives you the dimensions of the recording, but you need to look at the track's prefferedTransform to find the orientation of the recording. You might well find that the video width is actually the naturalSize 'height' depending on how the device was held during recording.
I see you set it on the composition, but you need to check it in order to assign the correct frames to your CALayers