ios - 从具有不同过渡动画的 UIImage 数组制作视频

Question

我正在关注 this code从 UIImage 数组 创建Video。从一幅图像过渡到另一幅图像时，这里没有动画。我想添加一些像这样的照片过渡效果:

1. TransitionFlipFromTop
2. TransitionFlipFromBottom
3. TransitionFlipFromLeft
4. TransitionFlipFromRight
5. TransitionCurlUp
6. TransitionCurlDown
7. TransitionCrossDissolve
8. 淡入
9. 淡出

这些动画可以通过 UIView.transition() 和 UIView.animate() 完成。

但是如何在从 UIImage 数组制作视频时应用这些过渡动画呢？我已经搜索了很多，但没有找到任何东西。

我也试过 HJImagesToVideo但它只提供 Crossfade transition 。

Answer 1

我被困在同一个问题中有一段时间了。由于这是一个很大的答案，它可能会让您感到厌烦，但我希望它能对您有所帮助。这是我在 Swift 3 中的回答。

理论:

首先，您必须使用图像阵列制作视频。关于这个问题有很多解决方案。稍微搜索一下，希望你能找到一个。如果没有，请参阅下面的代码。其次，您可能知道可以在视频上添加 CALayer。如果没有，搜索一下如何在视频上添加 CALayer。第三，您必须知道如何为 CALayer 设置动画。 Core Animation 将为您完成这项工作。关于这一点，有大量示例代码可供使用。搜索它。现在你有了一个 CALayer 并且你知道如何为它制作动画。 最后，您必须在视频中添加这个动画 CALayer。

代码:

1.使用您的图像数组制作视频

let outputSize = CGSize(width: 1920, height: 1280)
    let imagesPerSecond: TimeInterval = 3 //each image will be stay for 3 secs
    var selectedPhotosArray = [UIImage]()
    var imageArrayToVideoURL = NSURL()
    let audioIsEnabled: Bool = false //if your video has no sound
    var asset: AVAsset!

func buildVideoFromImageArray() {
        for image in 0..<5 {
            selectedPhotosArray.append(UIImage(named: "\(image + 1).JPG")!) //name of the images: 1.JPG, 2.JPG, 3.JPG, 4.JPG, 5.JPG
        }

        imageArrayToVideoURL = NSURL(fileURLWithPath: NSHomeDirectory() + "/Documents/video1.MP4")
        removeFileAtURLIfExists(url: imageArrayToVideoURL)
        guard let videoWriter = try? AVAssetWriter(outputURL: imageArrayToVideoURL as URL, fileType: AVFileTypeMPEG4) else {
            fatalError("AVAssetWriter error")
        }
        let outputSettings = [AVVideoCodecKey : AVVideoCodecH264, AVVideoWidthKey : NSNumber(value: Float(outputSize.width)), AVVideoHeightKey : NSNumber(value: Float(outputSize.height))] as [String : Any]
        guard videoWriter.canApply(outputSettings: outputSettings, forMediaType: AVMediaTypeVideo) else {
            fatalError("Negative : Can't apply the Output settings...")
        }
        let videoWriterInput = AVAssetWriterInput(mediaType: AVMediaTypeVideo, outputSettings: outputSettings)
        let sourcePixelBufferAttributesDictionary = [kCVPixelBufferPixelFormatTypeKey as String : NSNumber(value: kCVPixelFormatType_32ARGB), kCVPixelBufferWidthKey as String: NSNumber(value: Float(outputSize.width)), kCVPixelBufferHeightKey as String: NSNumber(value: Float(outputSize.height))]
        let pixelBufferAdaptor = AVAssetWriterInputPixelBufferAdaptor(assetWriterInput: videoWriterInput, sourcePixelBufferAttributes: sourcePixelBufferAttributesDictionary)
        if videoWriter.canAdd(videoWriterInput) {
            videoWriter.add(videoWriterInput)
        }
        if videoWriter.startWriting() {
            let zeroTime = CMTimeMake(Int64(imagesPerSecond),Int32(1))
            videoWriter.startSession(atSourceTime: zeroTime)

            assert(pixelBufferAdaptor.pixelBufferPool != nil)
            let media_queue = DispatchQueue(label: "mediaInputQueue")
            videoWriterInput.requestMediaDataWhenReady(on: media_queue, using: { () -> Void in
                let fps: Int32 = 1
                let framePerSecond: Int64 = Int64(self.imagesPerSecond)
                let frameDuration = CMTimeMake(Int64(self.imagesPerSecond), fps)
                var frameCount: Int64 = 0
                var appendSucceeded = true
                while (!self.selectedPhotosArray.isEmpty) {
                    if (videoWriterInput.isReadyForMoreMediaData) {
                        let nextPhoto = self.selectedPhotosArray.remove(at: 0)
                        let lastFrameTime = CMTimeMake(frameCount * framePerSecond, fps)
                        let presentationTime = frameCount == 0 ? lastFrameTime : CMTimeAdd(lastFrameTime, frameDuration)
                        var pixelBuffer: CVPixelBuffer? = nil
                        let status: CVReturn = CVPixelBufferPoolCreatePixelBuffer(kCFAllocatorDefault, pixelBufferAdaptor.pixelBufferPool!, &pixelBuffer)
                        if let pixelBuffer = pixelBuffer, status == 0 {
                            let managedPixelBuffer = pixelBuffer
                            CVPixelBufferLockBaseAddress(managedPixelBuffer, CVPixelBufferLockFlags(rawValue: CVOptionFlags(0)))
                            let data = CVPixelBufferGetBaseAddress(managedPixelBuffer)
                            let rgbColorSpace = CGColorSpaceCreateDeviceRGB()
                            let context = CGContext(data: data, width: Int(self.outputSize.width), height: Int(self.outputSize.height), bitsPerComponent: 8, bytesPerRow: CVPixelBufferGetBytesPerRow(managedPixelBuffer), space: rgbColorSpace, bitmapInfo: CGImageAlphaInfo.premultipliedFirst.rawValue)
                            context!.clear(CGRect(x: 0, y: 0, width: CGFloat(self.outputSize.width), height: CGFloat(self.outputSize.height)))
                            let horizontalRatio = CGFloat(self.outputSize.width) / nextPhoto.size.width
                            let verticalRatio = CGFloat(self.outputSize.height) / nextPhoto.size.height
                            //let aspectRatio = max(horizontalRatio, verticalRatio) // ScaleAspectFill
                            let aspectRatio = min(horizontalRatio, verticalRatio) // ScaleAspectFit
                            let newSize: CGSize = CGSize(width: nextPhoto.size.width * aspectRatio, height: nextPhoto.size.height * aspectRatio)
                            let x = newSize.width < self.outputSize.width ? (self.outputSize.width - newSize.width) / 2 : 0
                            let y = newSize.height < self.outputSize.height ? (self.outputSize.height - newSize.height) / 2 : 0
                            context?.draw(nextPhoto.cgImage!, in: CGRect(x: x, y: y, width: newSize.width, height: newSize.height))
                            CVPixelBufferUnlockBaseAddress(managedPixelBuffer, CVPixelBufferLockFlags(rawValue: CVOptionFlags(0)))
                            appendSucceeded = pixelBufferAdaptor.append(pixelBuffer, withPresentationTime: presentationTime)
                        } else {
                            print("Failed to allocate pixel buffer")
                            appendSucceeded = false
                        }
                    }
                    if !appendSucceeded {
                        break
                    }
                    frameCount += 1
                }
                videoWriterInput.markAsFinished()
                videoWriter.finishWriting { () -> Void in
                    print("-----video1 url = \(self.imageArrayToVideoURL)")

                    self.asset = AVAsset(url: self.imageArrayToVideoURL as URL)
                    self.exportVideoWithAnimation()
                }
            })
        }
    }

    func removeFileAtURLIfExists(url: NSURL) {
        if let filePath = url.path {
            let fileManager = FileManager.default
            if fileManager.fileExists(atPath: filePath) {
                do{
                    try fileManager.removeItem(atPath: filePath)
                } catch let error as NSError {
                    print("Couldn't remove existing destination file: \(error)")
                }
            }
        }
    }

2.为创建的视频添加动画(请仔细阅读所有评论部分。我认为阅读这些部分会弄清楚一些问题。)

func exportVideoWithAnimation() {
        let composition = AVMutableComposition()

        let track =  asset?.tracks(withMediaType: AVMediaTypeVideo)
        let videoTrack:AVAssetTrack = track![0] as AVAssetTrack
        let timerange = CMTimeRangeMake(kCMTimeZero, (asset?.duration)!)

        let compositionVideoTrack:AVMutableCompositionTrack = composition.addMutableTrack(withMediaType: AVMediaTypeVideo, preferredTrackID: CMPersistentTrackID())

        do {
            try compositionVideoTrack.insertTimeRange(timerange, of: videoTrack, at: kCMTimeZero)
            compositionVideoTrack.preferredTransform = videoTrack.preferredTransform
        } catch {
            print(error)
        }

        //if your video has sound, you don’t need to check this
        if audioIsEnabled {
            let compositionAudioTrack:AVMutableCompositionTrack = composition.addMutableTrack(withMediaType: AVMediaTypeAudio, preferredTrackID: CMPersistentTrackID())

            for audioTrack in (asset?.tracks(withMediaType: AVMediaTypeAudio))! {
                do {
                    try compositionAudioTrack.insertTimeRange(audioTrack.timeRange, of: audioTrack, at: kCMTimeZero)
                } catch {
                    print(error)
                }
            }
        }

        let size = videoTrack.naturalSize

        let videolayer = CALayer()
        videolayer.frame = CGRect(x: 0, y: 0, width: size.width, height: size.height)

        let parentlayer = CALayer()
        parentlayer.frame = CGRect(x: 0, y: 0, width: size.width, height: size.height)
        parentlayer.addSublayer(videolayer)

        ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
        //this is the animation part
        var time = [0.00001, 3, 6, 9, 12] //I used this time array to determine the start time of a frame animation. Each frame will stay for 3 secs, thats why their difference is 3
        var imgarray = [UIImage]()

        for image in 0..<5 {
            imgarray.append(UIImage(named: "\(image + 1).JPG")!)

            let nextPhoto = imgarray[image]

            let horizontalRatio = CGFloat(self.outputSize.width) / nextPhoto.size.width
            let verticalRatio = CGFloat(self.outputSize.height) / nextPhoto.size.height
            let aspectRatio = min(horizontalRatio, verticalRatio)
            let newSize: CGSize = CGSize(width: nextPhoto.size.width * aspectRatio, height: nextPhoto.size.height * aspectRatio)
            let x = newSize.width < self.outputSize.width ? (self.outputSize.width - newSize.width) / 2 : 0
            let y = newSize.height < self.outputSize.height ? (self.outputSize.height - newSize.height) / 2 : 0

            ///I showed 10 animations here. You can uncomment any of this and export a video to see the result.

            ///#1. left->right///
            let blackLayer = CALayer()
            blackLayer.frame = CGRect(x: -videoTrack.naturalSize.width, y: 0, width: videoTrack.naturalSize.width, height: videoTrack.naturalSize.height)
            blackLayer.backgroundColor = UIColor.black.cgColor

            let imageLayer = CALayer()
            imageLayer.frame = CGRect(x: x, y: y, width: newSize.width, height: newSize.height)
            imageLayer.contents = imgarray[image].cgImage
            blackLayer.addSublayer(imageLayer)

            let animation = CABasicAnimation()
            animation.keyPath = "position.x"
            animation.fromValue = -videoTrack.naturalSize.width
            animation.toValue = 2 * (videoTrack.naturalSize.width)
            animation.duration = 3
            animation.beginTime = CFTimeInterval(time[image])
            animation.fillMode = kCAFillModeForwards
            animation.isRemovedOnCompletion = false
            blackLayer.add(animation, forKey: "basic")

            ///#2. right->left///
//            let blackLayer = CALayer()
//            blackLayer.frame = CGRect(x: 2 * videoTrack.naturalSize.width, y: 0, width: videoTrack.naturalSize.width, height: videoTrack.naturalSize.height)
//            blackLayer.backgroundColor = UIColor.black.cgColor
//            
//            let imageLayer = CALayer()
//            imageLayer.frame = CGRect(x: x, y: y, width: newSize.width, height: newSize.height)
//            imageLayer.contents = imgarray[image].cgImage
//            blackLayer.addSublayer(imageLayer)
//            
//            let animation = CABasicAnimation()
//            animation.keyPath = "position.x"
//            animation.fromValue = 2 * (videoTrack.naturalSize.width)
//            animation.toValue = -videoTrack.naturalSize.width
//            animation.duration = 3
//            animation.beginTime = CFTimeInterval(time[image])
//            animation.fillMode = kCAFillModeForwards
//            animation.isRemovedOnCompletion = false
//            blackLayer.add(animation, forKey: "basic")

            ///#3. top->bottom///
//            let blackLayer = CALayer()
//            blackLayer.frame = CGRect(x: 0, y: 2 * videoTrack.naturalSize.height, width: videoTrack.naturalSize.width, height: videoTrack.naturalSize.height)
//            blackLayer.backgroundColor = UIColor.black.cgColor
//            
//            let imageLayer = CALayer()
//            imageLayer.frame = CGRect(x: x, y: y, width: newSize.width, height: newSize.height)
//            imageLayer.contents = imgarray[image].cgImage
//            blackLayer.addSublayer(imageLayer)
//            
//            let animation = CABasicAnimation()
//            animation.keyPath = "position.y"
//            animation.fromValue = 2 * videoTrack.naturalSize.height
//            animation.toValue = -videoTrack.naturalSize.height
//            animation.duration = 3
//            animation.beginTime = CFTimeInterval(time[image])
//            animation.fillMode = kCAFillModeForwards
//            animation.isRemovedOnCompletion = false
//            blackLayer.add(animation, forKey: "basic")

            ///#4. bottom->top///
//            let blackLayer = CALayer()
//            blackLayer.frame = CGRect(x: 0, y: -videoTrack.naturalSize.height, width: videoTrack.naturalSize.width, height: videoTrack.naturalSize.height)
//            blackLayer.backgroundColor = UIColor.black.cgColor
//            
//            let imageLayer = CALayer()
//            imageLayer.frame = CGRect(x: x, y: y, width: newSize.width, height: newSize.height)
//            imageLayer.contents = imgarray[image].cgImage
//            blackLayer.addSublayer(imageLayer)
//            
//            let animation = CABasicAnimation()
//            animation.keyPath = "position.y"
//            animation.fromValue = -videoTrack.naturalSize.height
//            animation.toValue = 2 * videoTrack.naturalSize.height
//            animation.duration = 3
//            animation.beginTime = CFTimeInterval(time[image])
//            animation.fillMode = kCAFillModeForwards
//            animation.isRemovedOnCompletion = false
//            blackLayer.add(animation, forKey: "basic")

            ///#5. opacity(1->0)(left->right)///
//            let blackLayer = CALayer()
//            blackLayer.frame = CGRect(x: -videoTrack.naturalSize.width, y: 0, width: videoTrack.naturalSize.width, height: videoTrack.naturalSize.height)
//            blackLayer.backgroundColor = UIColor.black.cgColor
//            
//            let imageLayer = CALayer()
//            imageLayer.frame = CGRect(x: x, y: y, width: newSize.width, height: newSize.height)
//            imageLayer.contents = imgarray[image].cgImage
//            blackLayer.addSublayer(imageLayer)
//            
//            let animation = CABasicAnimation()
//            animation.keyPath = "position.x"
//            animation.fromValue = -videoTrack.naturalSize.width
//            animation.toValue = 2 * (videoTrack.naturalSize.width)
//            animation.duration = 3
//            animation.beginTime = CFTimeInterval(time[image])
//            animation.fillMode = kCAFillModeForwards
//            animation.isRemovedOnCompletion = false
//            blackLayer.add(animation, forKey: "basic")
//            
//            let fadeOutAnimation = CABasicAnimation(keyPath: "opacity")
//            fadeOutAnimation.fromValue = 1
//            fadeOutAnimation.toValue = 0
//            fadeOutAnimation.duration = 3
//            fadeOutAnimation.beginTime = CFTimeInterval(time[image])
//            fadeOutAnimation.isRemovedOnCompletion = false
//            blackLayer.add(fadeOutAnimation, forKey: "opacity")

            ///#6. opacity(1->0)(right->left)///
//            let blackLayer = CALayer()
//            blackLayer.frame = CGRect(x: 2 * videoTrack.naturalSize.width, y: 0, width: videoTrack.naturalSize.width, height: videoTrack.naturalSize.height)
//            blackLayer.backgroundColor = UIColor.black.cgColor
//            
//            let imageLayer = CALayer()
//            imageLayer.frame = CGRect(x: x, y: y, width: newSize.width, height: newSize.height)
//            imageLayer.contents = imgarray[image].cgImage
//            blackLayer.addSublayer(imageLayer)
//            
//            let animation = CABasicAnimation()
//            animation.keyPath = "position.x"
//            animation.fromValue = 2 * videoTrack.naturalSize.width
//            animation.toValue = -videoTrack.naturalSize.width
//            animation.duration = 3
//            animation.beginTime = CFTimeInterval(time[image])
//            animation.fillMode = kCAFillModeForwards
//            animation.isRemovedOnCompletion = false
//            blackLayer.add(animation, forKey: "basic")
//            
//            let fadeOutAnimation = CABasicAnimation(keyPath: "opacity")
//            fadeOutAnimation.fromValue = 1
//            fadeOutAnimation.toValue = 0
//            fadeOutAnimation.duration = 3
//            fadeOutAnimation.beginTime = CFTimeInterval(time[image])
//            fadeOutAnimation.isRemovedOnCompletion = false
//            blackLayer.add(fadeOutAnimation, forKey: "opacity")

            ///#7. opacity(1->0)(top->bottom)///
//            let blackLayer = CALayer()
//            blackLayer.frame = CGRect(x: 0, y: 2 * videoTrack.naturalSize.height, width: videoTrack.naturalSize.width, height: videoTrack.naturalSize.height)
//            blackLayer.backgroundColor = UIColor.black.cgColor
//            
//            let imageLayer = CALayer()
//            imageLayer.frame = CGRect(x: x, y: y, width: newSize.width, height: newSize.height)
//            imageLayer.contents = imgarray[image].cgImage
//            blackLayer.addSublayer(imageLayer)
//            
//            let animation = CABasicAnimation()
//            animation.keyPath = "position.y"
//            animation.fromValue = 2 * videoTrack.naturalSize.height
//            animation.toValue = -videoTrack.naturalSize.height
//            animation.duration = 3
//            animation.beginTime = CFTimeInterval(time[image])
//            animation.fillMode = kCAFillModeForwards
//            animation.isRemovedOnCompletion = false
//            blackLayer.add(animation, forKey: "basic")
//            
//            let fadeOutAnimation = CABasicAnimation(keyPath: "opacity")
//            fadeOutAnimation.fromValue = 1
//            fadeOutAnimation.toValue = 0
//            fadeOutAnimation.duration = 3
//            fadeOutAnimation.beginTime = CFTimeInterval(time[image])
//            fadeOutAnimation.isRemovedOnCompletion = false
//            blackLayer.add(fadeOutAnimation, forKey: "opacity")

            ///#8. opacity(1->0)(bottom->top)///
//            let blackLayer = CALayer()
//            blackLayer.frame = CGRect(x: 0, y: -videoTrack.naturalSize.height, width: videoTrack.naturalSize.width, height: videoTrack.naturalSize.height)
//            blackLayer.backgroundColor = UIColor.black.cgColor
//            
//            let imageLayer = CALayer()
//            imageLayer.frame = CGRect(x: x, y: y, width: newSize.width, height: newSize.height)
//            imageLayer.contents = imgarray[image].cgImage
//            blackLayer.addSublayer(imageLayer)
//            
//            let animation = CABasicAnimation()
//            animation.keyPath = "position.y"
//            animation.fromValue = -videoTrack.naturalSize.height
//            animation.toValue = 2 * videoTrack.naturalSize.height
//            animation.duration = 3
//            animation.beginTime = CFTimeInterval(time[image])
//            animation.fillMode = kCAFillModeForwards
//            animation.isRemovedOnCompletion = false
//            blackLayer.add(animation, forKey: "basic")
//            
//            let fadeOutAnimation = CABasicAnimation(keyPath: "opacity")
//            fadeOutAnimation.fromValue = 1
//            fadeOutAnimation.toValue = 0
//            fadeOutAnimation.duration = 3
//            fadeOutAnimation.beginTime = CFTimeInterval(time[image])
//            fadeOutAnimation.isRemovedOnCompletion = false
//            blackLayer.add(fadeOutAnimation, forKey: "opacity")

            ///#9. scale(small->big->small)///
//            let blackLayer = CALayer()
//            blackLayer.frame = CGRect(x: 0, y: 0, width: videoTrack.naturalSize.width, height: videoTrack.naturalSize.height)
//            blackLayer.backgroundColor = UIColor.black.cgColor
//            blackLayer.opacity = 0
//            
//            let imageLayer = CALayer()
//            imageLayer.frame = CGRect(x: x, y: y, width: newSize.width, height: newSize.height)
//            imageLayer.contents = imgarray[image].cgImage
//            blackLayer.addSublayer(imageLayer)
//            
//            let scaleAnimation = CAKeyframeAnimation(keyPath: "transform.scale")
//            scaleAnimation.values = [0, 1.0, 0]
//            scaleAnimation.beginTime = CFTimeInterval(time[image])
//            scaleAnimation.duration = 3
//            scaleAnimation.isRemovedOnCompletion = false
//            blackLayer.add(scaleAnimation, forKey: "transform.scale")
//            
//            let fadeInOutAnimation = CABasicAnimation(keyPath: "opacity")
//            fadeInOutAnimation.fromValue = 1
//            fadeInOutAnimation.toValue = 1
//            fadeInOutAnimation.duration = 3
//            fadeInOutAnimation.beginTime = CFTimeInterval(time[image])
//            fadeInOutAnimation.isRemovedOnCompletion = false
//            blackLayer.add(fadeInOutAnimation, forKey: "opacity")

            ///#10. scale(big->small->big)///
//            let blackLayer = CALayer()
//            blackLayer.frame = CGRect(x: 0, y: 0, width: videoTrack.naturalSize.width, height: videoTrack.naturalSize.height)
//            blackLayer.backgroundColor = UIColor.black.cgColor
//            blackLayer.opacity = 0
//            
//            let imageLayer = CALayer()
//            imageLayer.frame = CGRect(x: x, y: y, width: newSize.width, height: newSize.height)
//            imageLayer.contents = imgarray[image].cgImage
//            blackLayer.addSublayer(imageLayer)
//            
//            let scaleAnimation = CAKeyframeAnimation(keyPath: "transform.scale")
//            scaleAnimation.values = [1, 0, 1]
//            scaleAnimation.beginTime = CFTimeInterval(time[image])
//            scaleAnimation.duration = 3
//            scaleAnimation.isRemovedOnCompletion = false
//            blackLayer.add(scaleAnimation, forKey: "transform.scale")
//            
//            let fadeOutAnimation = CABasicAnimation(keyPath: "opacity")
//            fadeOutAnimation.fromValue = 1
//            fadeOutAnimation.toValue = 1
//            fadeOutAnimation.duration = 3
//            fadeOutAnimation.beginTime = CFTimeInterval(time[image])
//            fadeOutAnimation.isRemovedOnCompletion = false
//            blackLayer.add(fadeOutAnimation, forKey: "opacity")

            parentlayer.addSublayer(blackLayer)
        }
        ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

        let layercomposition = AVMutableVideoComposition()
        layercomposition.frameDuration = CMTimeMake(1, 30)
        layercomposition.renderSize = size
        layercomposition.animationTool = AVVideoCompositionCoreAnimationTool(postProcessingAsVideoLayer: videolayer, in: parentlayer)
        let instruction = AVMutableVideoCompositionInstruction()
        instruction.timeRange = CMTimeRangeMake(kCMTimeZero, composition.duration)
        let videotrack = composition.tracks(withMediaType: AVMediaTypeVideo)[0] as AVAssetTrack
        let layerinstruction = AVMutableVideoCompositionLayerInstruction(assetTrack: videotrack)
        instruction.layerInstructions = [layerinstruction]
        layercomposition.instructions = [instruction]

        let animatedVideoURL = NSURL(fileURLWithPath: NSHomeDirectory() + "/Documents/video2.mp4")
        removeFileAtURLIfExists(url: animatedVideoURL)

        guard let assetExport = AVAssetExportSession(asset: composition, presetName:AVAssetExportPresetHighestQuality) else {return}
        assetExport.videoComposition = layercomposition
        assetExport.outputFileType = AVFileTypeMPEG4
        assetExport.outputURL = animatedVideoURL as URL
        assetExport.exportAsynchronously(completionHandler: {
            switch assetExport.status{
            case  AVAssetExportSessionStatus.failed:
                print("failed \(String(describing: assetExport.error))")
            case AVAssetExportSessionStatus.cancelled:
                print("cancelled \(String(describing: assetExport.error))")
            default:
                print("Exported")
            }
        })
    }

不要忘记导入 AVFoundation