Overlaying text on video is very slow any faster alternatives - ios

Question

let asset = AVURLAsset(url: videoURL)
let composition = AVMutableComposition()
guard
let compositionTrack = composition.addMutableTrack(
withMediaType: .video, preferredTrackID: kCMPersistentTrackID_Invalid),
let assetTrack = asset.tracks(withMediaType: .video).first
else {
print("Something is wrong with the asset.")
onComplete(nil)
return
}
do {
let timeRange = CMTimeRange(start: .zero, duration: asset.duration)
try compositionTrack.insertTimeRange(timeRange, of: assetTrack, at: .zero)
if let audioAssetTrack = asset.tracks(withMediaType: .audio).first,
let compositionAudioTrack = composition.addMutableTrack(
withMediaType: .audio,
preferredTrackID: kCMPersistentTrackID_Invalid) {
try compositionAudioTrack.insertTimeRange(
timeRange,
of: audioAssetTrack,
at: .zero)
}
} catch {
//print(error)
onComplete(nil)
return
}
compositionTrack.preferredTransform = assetTrack.preferredTransform
let videoInfo = orientation(from: assetTrack.preferredTransform)
let videoSize: CGSize
if videoInfo.isPortrait {
videoSize = CGSize(
width: assetTrack.naturalSize.height,
height: assetTrack.naturalSize.width)
} else {
videoSize = assetTrack.naturalSize
}
let videoLayer = CALayer()
videoLayer.frame = CGRect(origin: .zero, size: videoSize)
let textLayer = CATextLayer()
textLayer.string = mainTextview.text
textLayer.shouldRasterize = true
textLayer.rasterizationScale = UIScreen.main.scale
//textLayer.backgroundColor = UIColor.black.cgColor
switch textAlignment {
case .center:
textLayer.alignmentMode = .center
case .justified:
textLayer.alignmentMode = .justified
case .left:
textLayer.alignmentMode = .left
case .right:
textLayer.alignmentMode = .right
default:
textLayer.alignmentMode = .center
}
textLayer.isWrapped = true
textLayer.foregroundColor = mainTextview.textColor?.cgColor
textLayer.fontSize = 70
switch textWeight {
case .bold:
textLayer.font = UIFont.systemFont(ofSize: 0, weight: .bold)
case .light:
textLayer.font = UIFont.systemFont(ofSize: 0, weight: .light)
case .regular:
textLayer.font = UIFont.systemFont(ofSize: 0, weight: .regular)
case .medium:
textLayer.font = UIFont.systemFont(ofSize: 0, weight: .medium)
}
switch textviewPosition {
case .Center:
textLayer.frame = CGRect(x: 0, y: videoSize.height * 0.30, width: videoSize.width, height: 500)
case .Top:
textLayer.frame = CGRect(x: 0, y: videoSize.height * 0.60, width: videoSize.width, height: 500)
case .Bottom:
textLayer.frame = CGRect(x: 10, y: 0, width: videoSize.width, height: 500)
}
textLayer.displayIfNeeded()
let outputLayer = CALayer()
outputLayer.frame = CGRect(origin: .zero, size: videoSize)
outputLayer.addSublayer(videoLayer)
outputLayer.addSublayer(textLayer)
let videoComposition = AVMutableVideoComposition()
videoComposition.renderSize = videoSize
videoComposition.frameDuration = CMTime(value: 1, timescale: 30)
videoComposition.animationTool = AVVideoCompositionCoreAnimationTool(
postProcessingAsVideoLayer: videoLayer,
in: outputLayer)
let instruction = AVMutableVideoCompositionInstruction()
instruction.timeRange = CMTimeRange(
start: .zero,
duration: composition.duration)
videoComposition.instructions = [instruction]
let layerInstruction = compositionLayerInstruction(
for: compositionTrack,
assetTrack: assetTrack)
instruction.layerInstructions = [layerInstruction]
guard let export = AVAssetExportSession(
asset: composition,
presetName: AVAssetExportPresetHighestQuality)
else {
//print("Cannot create export session.")
onComplete(nil)
return
}
let videoName = UUID().uuidString
let exportURL = URL(fileURLWithPath: NSTemporaryDirectory())
.appendingPathComponent(videoName)
.appendingPathExtension(".mp4")
export.videoComposition = videoComposition
export.outputFileType = .mp4
export.outputURL = exportURL
export.exportAsynchronously {
DispatchQueue.main.async {
switch export.status {
case .completed:
onComplete(exportURL)
default:
onComplete(nil)
break
}
}
}
}
This is the function I use to overlay the text on video (videoURL), I pass in the url for the video which is saved in the document directory and use a text view already created for the user to retrieve the text, weight, font and alignment for the overlay thanks. Majority of time this process takes 15 seconds which is a long time for users to wait.

Answer 1

Exporting video is labor-intensive and takes significant time, and there's nothing you can do about that.
However, the process is asynchronous so there is no need to make the user "wait". Also, the exporter vends a Progress object, so you can easily show progress as a psychological trick (it is amazing how time flies when you're watching a progress indicator).

Answer 2

Thanks for your response under where I initiated the AVAssetExportSession I added a timer:
self.exportTimer = Timer.scheduledTimer(timeInterval: 0.1, target: self, selector: #selector(displayData), userInfo: nil, repeats: true)
Now I can correctly update the display using this method:
#objc private func displayData() {
self.progressBar.progress = exportSession.progress;
if self.progressBar.progress > .99) {
self.exportTimer.invalidate()
}
}
I also added Invalidate() to the export.status switch statement for when there is an error.