swift - 索引0超出了具有asset.tracks(withMediaType :)的空NSArray的范围

我试图通过精确的大小来裁剪视频，但asset.tracks（with mediatype:AVMediaType.video）[0]行出错，该行返回的索引0超出了空的界限。我确定在那个网址下面有一段视频。。。
iOS:[NSArray0 objectAtIndex:]索引0超出了带有asset.tracks的空NSArray的界限（带mediatype: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?

最佳答案

在处理视频处理时，需要确保所有导入的文件都具有可接受的扩展名，例如执行以下操作

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

if acceptableVideoExtensions.contains(videoURL.pathExtension) {

   // Process the video
}
else {

    //Alert the user
}

关于swift - 索引0超出了具有asset.tracks(withMediaType :)的空NSArray的范围，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/53931387/