index 0 beyond bounds for empty NSArray with asset.tracks(withMediaType:)

Question

I try to crop a video by taking a precise size of it, but I have an error with the asset.tracks(withMediaType: AVMediaType.video)[0] line that returns me a index 0 beyond bounds for empty. I precise that there is a video under that url...

iOS: [NSArray0 objectAtIndex:] index 0 beyond bounds for empty NSArray with asset.tracks(withMediaType: AVMediaType.video)[0]

    // input file
            let composition = AVMutableComposition()
            composition.addMutableTrack(withMediaType: .video, preferredTrackID: kCMPersistentTrackID_Invalid)

            // input clip
            let asset = AVAsset(url: URL(fileURLWithPath: video))

            let videoTrack: AVAssetTrack = asset.tracks(withMediaType: AVMediaType.video)[0]  
//=> problem is here

            // crop clip to screen ratio
            let orientation: UIInterfaceOrientation = self.orientation(forTrack: asset)

            // make render size square
            let videoComposition = AVMutableVideoComposition.init()
            let height: CGFloat = 960
            let width: CGFloat = 960

            videoComposition.renderSize = CGSize(width: CGFloat(width), height: CGFloat(height))
            videoComposition.frameDuration = CMTimeMake(1, 30)

            let instruction = AVMutableVideoCompositionInstruction()
            instruction.timeRange = CMTimeRangeMake(kCMTimeZero, CMTimeMakeWithSeconds(60, 30))

            // rotate and position video
            let transformer = AVMutableVideoCompositionLayerInstruction(assetTrack: videoTrack)

            var txWidth: CGFloat = (videoTrack.naturalSize.width - width) / 2
            let txHeight: CGFloat = (videoTrack.naturalSize.height - height) / 2

            if orientation == .portrait || orientation == .landscapeRight {
                // invert translation
                txWidth *= -1
            }

            // t1: rotate and position video since it may have been cropped to screen ratio
            let t1: CGAffineTransform = videoTrack.preferredTransform.translatedBy(x: txWidth, y: -txHeight)

            transformer.setTransform(t1, at: kCMTimeZero)


            instruction.layerInstructions = [transformer]
            videoComposition.instructions = [instruction] as [AVVideoCompositionInstructionProtocol]

            // export
            let exporter = AVAssetExportSession(asset: asset, presetName: AVAssetExportPresetHighestQuality)
            exporter?.videoComposition = videoComposition
            exporter?.outputURL = URL(fileURLWithPath: video)
            exporter?.outputFileType = .mov

            exporter?.exportAsynchronously(completionHandler: {
                print("Exporting done!")
            })

Any ideas?

Answer 1

When dealing with video processing you need to make sure that all imported files are of an acceptable extension such as doing this

let acceptableVideoExtensions = ["mov", "mp4", "m4v"]

if acceptableVideoExtensions.contains(videoURL.pathExtension) {

   // Process the video
}
else {

    //Alert the user
}