Adding text subtitles to video track (in Swift) fails with error code -11841

Question

I have been struggling with adding text subtitles to videos for a while. I have added some links that I referred in detail, but they are not helping.

In below code, I a

Answer 1

When I tried this the subtitle did not appear. I fixed it by swapping the order of the sublayers.

i.e

parentLayer.addSublayer(videoLayer)

parentLayer.addSubLayer(backgroundLayer)