Avfoundation AVAssetExportSession通过EXC_BAD_指令

我正在做一个从图像到视频的幻灯片项目

我对我的项目有几个过渡影响。 我使用的是AVFoundation库，但在iOS 14上转换不起作用。 当我异步调用exportAsynchronously（completionHandler:{}时，它抛出错误（

线程26:EXC\u BAD\u指令（code=EXC\u I386\u INVOP，subcode=0x0）

）。 我无法理解代码的问题。是iOS14版本问题还是其他问题

下面是我正在使用的代码

let layercomposition = AVMutableVideoComposition()
        layercomposition.frameDuration = CMTimeMake(value: 1, timescale: 30)
        layercomposition.renderSize = size
        layercomposition.animationTool = AVVideoCompositionCoreAnimationTool(postProcessingAsVideoLayer: videolayer, in: parentlayer)
        let instruction = AVMutableVideoCompositionInstruction()
        instruction.timeRange = CMTimeRangeMake(start: CMTime.zero, duration: composition.duration)
        let videotrack = composition.tracks(withMediaType: AVMediaType.video)[0] as AVAssetTrack
        let layerinstruction = AVMutableVideoCompositionLayerInstruction(assetTrack: videotrack)
        instruction.layerInstructions = [layerinstruction]
        layercomposition.instructions = [instruction]
        
        var today: String = String()
        today = getCurrentTimeAsString()
        
        
        
        videoURLFromSelectedPhotos = NSURL(fileURLWithPath: NSHomeDirectory() + "/Documents/PhotoSlide/PicSlide_\(today).mp4")
        removeFileAtURLIfExists(url: videoURLFromSelectedPhotos)
        
        guard let assetExport = AVAssetExportSession(asset: composition, presetName:AVAssetExportPresetHighestQuality) else {return}
        assetExport.videoComposition = layercomposition
        assetExport.outputFileType = AVFileType.mp4
        assetExport.outputURL = videoURLFromSelectedPhotos as URL
        
        
        
     
        // MARK:  exportAsynchronously crash on iso 14
        
        assetExport.exportAsynchronously(completionHandler: {})