我正在尝试使用AVVideoComposition 在视频顶部添加一些文本并保存视频。 这是我使用的代码:

我 创建一个AVMutableComposition 和AVVideoComposition

var mutableComp =          AVMutableComposition()
var mutableVidComp =       AVMutableVideoComposition()
var compositionSize :      CGSize?

func configureAsset(){

    let options =               [AVURLAssetPreferPreciseDurationAndTimingKey : "true"]
    let videoAsset =             AVURLAsset(url: Bundle.main.url(forResource: "Car", withExtension: "mp4")! , options : options)
    let videoAssetSourceTrack =  videoAsset.tracks(withMediaType: AVMediaTypeVideo).first! as AVAssetTrack

    compositionSize = videoAssetSourceTrack.naturalSize

    let mutableVidTrack =       mutableComp.addMutableTrack(withMediaType: AVMediaTypeVideo, preferredTrackID: kCMPersistentTrackID_Invalid)
    let trackRange =            CMTimeRangeMake(kCMTimeZero, videoAsset.duration)

    do {
        try mutableVidTrack.insertTimeRange( trackRange, of: videoAssetSourceTrack, at: kCMTimeZero)

        mutableVidTrack.preferredTransform = videoAssetSourceTrack.preferredTransform

    }catch { print(error) }

    snapshot =       mutableComp
    mutableVidComp = AVMutableVideoComposition(propertiesOf: videoAsset)
 }

II 设置图层

  func applyVideoEffectsToComposition()   {

    // 1 - Set up the text layer
    let subTitle1Text =            CATextLayer()
    subTitle1Text.font =           "Helvetica-Bold" as CFTypeRef
    subTitle1Text.frame =           CGRect(x: self.view.frame.midX - 60 , y: self.view.frame.midY - 50, width: 120, height: 100)
    subTitle1Text.string =         "Bench"
    subTitle1Text.foregroundColor = UIColor.black.cgColor
    subTitle1Text.alignmentMode =   kCAAlignmentCenter

    // 2 - The usual overlay
    let overlayLayer = CALayer()
    overlayLayer.addSublayer(subTitle1Text)
    overlayLayer.frame = CGRect(x: 0, y: 0, width: compositionSize!.width, height: compositionSize!.height)
    overlayLayer.masksToBounds = true


    // 3 - set up the parent layer
    let parentLayer =   CALayer()
    let videoLayer =    CALayer()
    parentLayer.frame = CGRect(x: 0, y: 0, width: compositionSize!.width, height: compositionSize!.height)
    videoLayer.frame =  CGRect(x: 0, y: 0, width: compositionSize!.width, height: compositionSize!.height)

    parentLayer.addSublayer(videoLayer)
    parentLayer.addSublayer(overlayLayer)

    mutableVidComp.animationTool = AVVideoCompositionCoreAnimationTool(postProcessingAsVideoLayer: videoLayer, in: parentLayer)

 }

III .使用 AVMutbaleVideoComposition

func saveAsset (){

    func deleteFile(_ filePath:URL) {

        guard FileManager.default.fileExists(atPath: filePath.path) else { return }

        do {
            try    FileManager.default.removeItem(atPath: filePath.path) }
        catch {fatalError("Unable to delete file: \(error) : \(#function).")} }


    let documentsDirectory = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0] as URL
    let filePath =           documentsDirectory.appendingPathComponent("rendered-audio.mp4")
    deleteFile(filePath)

    if let exportSession = AVAssetExportSession(asset: mutableComp , presetName: AVAssetExportPresetHighestQuality){

        exportSession.videoComposition = mutableVidComp

        //  exportSession.canPerformMultiplePassesOverSourceMediaData = true
        exportSession.outputURL =                   filePath
        exportSession.shouldOptimizeForNetworkUse = true
        exportSession.timeRange =                   CMTimeRangeMake(kCMTimeZero, mutableComp.duration)
        exportSession.outputFileType =              AVFileTypeQuickTimeMovie



        exportSession.exportAsynchronously {
            print("finished: \(filePath) :  \(exportSession.status.rawValue) ")

            if exportSession.status.rawValue == 4 {

                print("Export failed -> Reason: \(exportSession.error!.localizedDescription))")
                print(exportSession.error!)

            }

        }

    }

}

然后我在 viewDidLoad 方法中运行所有三个方法以进行快速测试。问题是当我运行应用程序时，导出的结果是没有标题的原始视频。

我在这里错过了什么？

更新

我注意到添加一个 subTitle1Text.backgroundColor 属性 代码的 II 部分使与 subTitle1Text.frame 对应的彩色 CGRect 在导出时出现在视频顶部。

(See Image)

当此代码被修改为使用 AVSynchronizedLayer 进行播放时，可以在视频的顶部看到所需的层，上面有文本。 所以也许这是 AVFoundation 本身的错误。

我想我只能选择使用 customVideoCompositorClass。问题在于渲染视频需要花费大量时间。这是一个使用 AVVideoCompositing 的示例

最佳答案

这是我在项目中使用的完整工作代码。它将在底部 (0,0) 显示 CATextLayer。在导出 session 完成后，它将替换播放器项目中的新路径。我使用了 Objective C 代码中的一个模型来获取方向。请在设备中进行测试。 AVPLayer 将无法在模拟器中正确显示文本层。

let composition = AVMutableComposition.init()

    let videoComposition = AVMutableVideoComposition()
    videoComposition.frameDuration = CMTimeMake(1, 30)
    videoComposition.renderScale  = 1.0

    let compositionCommentaryTrack: AVMutableCompositionTrack? = composition.addMutableTrack(withMediaType: AVMediaTypeAudio, preferredTrackID: kCMPersistentTrackID_Invalid)


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


    let clipVideoTrack:AVAssetTrack = self.currentAsset.tracks(withMediaType: AVMediaTypeVideo)[0]

    let audioTrack: AVAssetTrack? = self.currentAsset.tracks(withMediaType: AVMediaTypeAudio)[0]

    try? compositionCommentaryTrack?.insertTimeRange(CMTimeRangeMake(kCMTimeZero, self.currentAsset.duration), of: audioTrack!, at: kCMTimeZero)

    try? compositionVideoTrack?.insertTimeRange(CMTimeRangeMake(kCMTimeZero, self.currentAsset.duration), of: clipVideoTrack, at: kCMTimeZero)

    let orientation = VideoModel.videoOrientation(self.currentAsset)
    var isPortrait = false

    switch orientation {
    case .landscapeRight:
        isPortrait = false
    case .landscapeLeft:
        isPortrait = false
    case .portrait:
        isPortrait = true
    case .portraitUpsideDown:
        isPortrait = true
    }

    var naturalSize = clipVideoTrack.naturalSize

    if isPortrait
    {
        naturalSize = CGSize.init(width: naturalSize.height, height: naturalSize.width)
    }

    videoComposition.renderSize = naturalSize

    let scale = CGFloat(1.0)

    var transform = CGAffineTransform.init(scaleX: CGFloat(scale), y: CGFloat(scale))

    switch orientation {
    case .landscapeRight: break
    // isPortrait = false
    case .landscapeLeft:
        transform = transform.translatedBy(x: naturalSize.width, y: naturalSize.height)
        transform = transform.rotated(by: .pi)
    case .portrait:
        transform = transform.translatedBy(x: naturalSize.width, y: 0)
        transform = transform.rotated(by: CGFloat(M_PI_2))
    case .portraitUpsideDown:break
    }

    let frontLayerInstruction = AVMutableVideoCompositionLayerInstruction(assetTrack: compositionVideoTrack!)
    frontLayerInstruction.setTransform(transform, at: kCMTimeZero)

    let MainInstruction = AVMutableVideoCompositionInstruction()
    MainInstruction.timeRange = CMTimeRangeMake(kCMTimeZero, composition.duration)
    MainInstruction.layerInstructions = [frontLayerInstruction]
    videoComposition.instructions = [MainInstruction]

    let parentLayer = CALayer.init()
    parentLayer.frame = CGRect.init(x: 0, y: 0, width: naturalSize.width, height: naturalSize.height)

    let videoLayer = CALayer.init()
    videoLayer.frame = parentLayer.frame


    let layer = CATextLayer()
    layer.string = "HELLO ALL"
    layer.foregroundColor = UIColor.white.cgColor
    layer.backgroundColor = UIColor.orange.cgColor
    layer.fontSize = 32
    layer.frame = CGRect.init(x: 0, y: 0, width: 300, height: 100)

    var rct = layer.frame;

    let widthScale = self.playerView.frame.size.width/naturalSize.width

    rct.size.width /= widthScale
    rct.size.height /= widthScale
    rct.origin.x /= widthScale
    rct.origin.y /= widthScale



    parentLayer.addSublayer(videoLayer)
    parentLayer.addSublayer(layer)

    videoComposition.animationTool = AVVideoCompositionCoreAnimationTool.init(postProcessingAsVideoLayer: videoLayer, in: parentLayer)

    let documentsPath = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0]
    let videoPath = documentsPath+"/cropEditVideo.mov"

    let fileManager = FileManager.default

    if fileManager.fileExists(atPath: videoPath)
    {
        try! fileManager.removeItem(atPath: videoPath)
    }

    print("video path \(videoPath)")

    var exportSession = AVAssetExportSession.init(asset: composition, presetName: AVAssetExportPresetHighestQuality)
    exportSession?.videoComposition = videoComposition
    exportSession?.outputFileType = AVFileTypeQuickTimeMovie
    exportSession?.outputURL = URL.init(fileURLWithPath: videoPath)
    exportSession?.videoComposition = videoComposition
    var exportProgress: Float = 0
    let queue = DispatchQueue(label: "Export Progress Queue")
    queue.async(execute: {() -> Void in
        while exportSession != nil {
            //                int prevProgress = exportProgress;
            exportProgress = (exportSession?.progress)!
            print("current progress == \(exportProgress)")
            sleep(1)
        }
    })

    exportSession?.exportAsynchronously(completionHandler: {


        if exportSession?.status == AVAssetExportSessionStatus.failed
        {
            print("Failed \(exportSession?.error)")
        }else if exportSession?.status == AVAssetExportSessionStatus.completed
        {
            exportSession = nil

            let asset = AVAsset.init(url: URL.init(fileURLWithPath: videoPath))
            DispatchQueue.main.async {
                let item = AVPlayerItem.init(asset: asset)


                self.player.replaceCurrentItem(with: item)

                let assetDuration = CMTimeGetSeconds(composition.duration)
                self.progressSlider.maximumValue = Float(assetDuration)

                self.syncLayer.removeFromSuperlayer()
                self.lblIntro.isHidden = true

                self.player.play()
                //                    let url =  URL.init(fileURLWithPath: videoPath)
                //                    let activityVC = UIActivityViewController(activityItems: [url], applicationActivities: [])
                //                    self.present(activityVC, animated: true, completion: nil)
            }

        }
    })

下面是我的VideoModel类的代码

-(AVCaptureVideoOrientation)videoOrientation:(AVAsset *)asset
{
    AVCaptureVideoOrientation result = 0;
    NSArray *tracks = [asset tracksWithMediaType:AVMediaTypeVideo];
    if([tracks    count] > 0) {
        AVAssetTrack *videoTrack = [tracks objectAtIndex:0];
        CGAffineTransform t = videoTrack.preferredTransform;
        // Portrait
        if(t.a == 0 && t.b == 1.0 && t.c == -1.0 && t.d == 0)
        {
            result = AVCaptureVideoOrientationPortrait;
        }
        // PortraitUpsideDown
        if(t.a == 0 && t.b == -1.0 && t.c == 1.0 && t.d == 0)  {

            result = AVCaptureVideoOrientationPortraitUpsideDown;
        }
        // LandscapeRight
        if(t.a == 1.0 && t.b == 0 && t.c == 0 && t.d == 1.0)
        {
            result = AVCaptureVideoOrientationLandscapeRight;
        }
        // LandscapeLeft
        if(t.a == -1.0 && t.b == 0 && t.c == 0 && t.d == -1.0)
        {
            result = AVCaptureVideoOrientationLandscapeLeft;
        }
    }
    return result;
}

如果您在这方面需要更多帮助，请告诉我。

关于ios - swift 3 : How to export video with text using AVVideoComposition，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/45198189/