VideoComposition not honoring instructions

Question

Since updating to iOS 13 my video composition I use to fade a video in and out is broken. This is my code which worked correctly up until installing iOS 13.

Now when I export the video there is sound and just a black screen.

let urlAsset = AVURLAsset(url: inputURL, options: nil)      
guard let exportSession = AVAssetExportSession(asset: urlAsset, presetName: AVAssetExportPresetHighestQuality) else { handler(nil)
     return
}
exportSession.outputURL = outputURL
exportSession.outputFileType = AVFileType.m4v
exportSession.shouldOptimizeForNetworkUse = true

let composition = AVMutableVideoComposition(propertiesOf: urlAsset)

let clipVideoTrack = urlAsset.tracks(withMediaType: AVMediaType.video)[0]

let timeDuration = CMTimeMake(value: 1, timescale: 1)

let layer = AVMutableVideoCompositionLayerInstruction(assetTrack: clipVideoTrack)

// MARK: Fade in effect
layer.setOpacityRamp(fromStartOpacity: 0.0, toEndOpacity: 1.0, timeRange: CMTimeRange(start: CMTime.zero, duration: timeDuration))

// MARK: Fade out effect
let startTime = CMTimeSubtract(urlAsset.duration, CMTimeMake(value: 1, timescale: 1))

layer.setOpacityRamp(
       fromStartOpacity: 1.0,
       toEndOpacity: 0.0,
       timeRange: CMTimeRangeMake(start: startTime, duration: timeDuration)
)

let instruction = AVMutableVideoCompositionInstruction()
instruction.layerInstructions = [layer]
instruction.timeRange = CMTimeRange(start: CMTime.zero, duration: urlAsset.duration)


composition.instructions = [instruction]

exportSession.videoComposition = composition

exportSession.exportAsynchronously { () -> Void in
       handler(exportSession)
       print("composition has completed")
}

Answer 1

Apple said there was a bug affecting some instructions for compositions. This was fixed in iOS 13.1. I updated and ran the function and the fade in and out worked as it was before iOS 13 update.