AVAssetExportSession 不适用于设备，但适用于模拟器（AVFoundationErrorDomain 代码 = -11800，未知错误代码 -12780）

Question

编辑：为了让任何有兴趣检查这个问题的人更容易，我在 这个 github 存储库中添加了一个演示项目 。

问题

我见过几个有相同错误的问题，但在那里找到的解决方案都没有帮助我。 想我会试试我的运气。

我正在尝试按原样导出视频，主要是为了了解 AVFoundation 和 AVAssetExportSession。 我的导出在模拟器上运行良好，但在我尝试过的任何 iOS 设备（即 iPhone X 和运行 iOS 12 的 iPhone XR）上都不起作用。 我主要按照此链接上的 Ray Wenderleich 教程执行视频导出： https ://www.raywenderlich.com/2734-avfoundation-tutorial-adding-overlays-and-animations-to-videos

将不胜感激有关该主题的任何帮助。 我的代码如下：

检索我添加到名为 Demo.mp4 的 App Bundle 的视频的 URL：

@objc func export() {
    let urlString = Bundle.main.path(forResource: "Demo", ofType: ".mp4")!
    let url = URL(fileURLWithPath: urlString)
    ExportManager.shared.exportWithAVFoundation(url:url) { (outputUrl, errorString) in
        if let outputUrl = outputUrl {
            self.playVideo(url: outputUrl)
        } else if let errorString = errorString {
            print("ERROR: \(errorString)")
        }
    }
}

我在 ExportManager 中的导出功能如下（抱歉很长）

func exportWithAVFoundation(url: URL, completion: @escaping (_ outputUrl: URL?, _ errorString: String?) -> ()) {
    let asset = AVAsset(url: url)
    print("URL IS \(url)")
    guard let avAssetTrack = asset.tracks(withMediaType: .video).first else {
        completion(nil, "Couldn't Create Asset Track")
        return
    }

    let mutableComposition = AVMutableComposition()
    guard let videoTrack = mutableComposition.addMutableTrack(withMediaType: .video, preferredTrackID: kCMPersistentTrackID_Invalid) else { return }
    try? videoTrack.insertTimeRange(CMTimeRange(start: .zero, duration: asset.duration), of: avAssetTrack, at: .zero)
    videoTrack.preferredTransform = avAssetTrack.preferredTransform

    if let audioAssetTrack = asset.tracks(withMediaType: .audio).first {
        let audioTrack = mutableComposition.addMutableTrack(withMediaType: .audio, preferredTrackID: kCMPersistentTrackID_Invalid)
        try? audioTrack?.insertTimeRange(CMTimeRange(start: .zero, duration: asset.duration), of: audioAssetTrack, at: .zero)
    }

    let mainInstruction = AVMutableVideoCompositionInstruction()
    mainInstruction.timeRange = CMTimeRange(start: .zero, duration: asset.duration)

    let videoLayerInstruction = AVMutableVideoCompositionLayerInstruction(assetTrack: videoTrack)

    // Fix video orientation
    var videoAssetOrientation = UIImage.Orientation.up
    var isVideoAssetPortrait = false
    let videoTransform = avAssetTrack.preferredTransform

    switch (videoTransform.a, videoTransform.b, videoTransform.c, videoTransform.c) {
    case (0, 1.0, -1.0, 0):
        videoAssetOrientation = .right
        isVideoAssetPortrait = true
    case(0, -1.0, 1.0, 0):
        videoAssetOrientation = .left
        isVideoAssetPortrait = true
    case(1.0, 0, 0, 1.0):
        videoAssetOrientation = .up
    case(-1.0, 0, 0, -1.0):
        videoAssetOrientation = .down
    default:
        break
    }

    var naturalSize = avAssetTrack.naturalSize
    switch (videoAssetOrientation, isVideoAssetPortrait) {
    case (.right, true):
        naturalSize = CGSize(width: avAssetTrack.naturalSize.height, height: avAssetTrack.naturalSize.width)
    case (.left, true):
        naturalSize = CGSize(width: avAssetTrack.naturalSize.height, height: avAssetTrack.naturalSize.width)
    case (.leftMirrored, true):
        naturalSize = CGSize(width: avAssetTrack.naturalSize.height, height: avAssetTrack.naturalSize.width)
    case (.rightMirrored, true):
        naturalSize = CGSize(width: avAssetTrack.naturalSize.height, height: avAssetTrack.naturalSize.width)
    default:
        break
    }

    videoLayerInstruction.setTransform(avAssetTrack.preferredTransform, at: .zero)
    videoLayerInstruction.setOpacity(0, at: asset.duration)

    mainInstruction.layerInstructions = [videoLayerInstruction]

    let mainCompositionInstruction = AVMutableVideoComposition()

    mainCompositionInstruction.renderSize = naturalSize
    mainCompositionInstruction.instructions = [mainInstruction]
    mainCompositionInstruction.frameDuration = CMTimeMake(value: 1, timescale: 30);

    let documentsDirectoryURL = createPath()

    guard let exporter = AVAssetExportSession(asset: mutableComposition, presetName: AVAssetExportPresetHighestQuality) else {
        print("Couldnt create AVAssetExportSession")

        completion(nil, "Couldn't Create AVAssetExportSession")
        return
    }

    exporter.outputURL = documentsDirectoryURL
    exporter.outputFileType = .mov
    exporter.shouldOptimizeForNetworkUse = true
    exporter.videoComposition = mainCompositionInstruction

    exporter.exportAsynchronously {
        if let error = exporter.error {
            print(error)
            completion(nil, error.localizedDescription)
            return
        }

        completion(exporter.outputURL, nil)
        print("Finished Exporting")
    }
}

我尝试做的一些事情是将 AudioTrack 添加到作品中（我之前没有添加）。 没有帮助它在实际设备上工作，但至少我导出的视频现在有音频。

我还尝试将预设质量更改为直通而不是最高质量，因为我从其他线程中读到这可能会有所帮助，但无济于事。

编辑：

添加了 createPath 函数：

func createPath() -> URL {
    let paths = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)
    let documentDirectory = paths.first!
    let myPathDocs = documentDirectory.appending("FinalVideo.mov")
    let url = URL(fileURLWithPath: myPathDocs)

    if FileManager.default.fileExists(atPath: myPathDocs) {
        try? FileManager.default.removeItem(atPath: myPathDocs)
    }

    return url
}

注意：createPath() 只是在目录中创建一个有效的路径来保存导出的视频。如果在导出之前该路径中存在文件，它将被删除。

Answer 1

问题是您将字符串附加到另一个字符串，导致文件路径错误，例如file:///var/mobile/Containers/Data/Application/<stripped>/DocumentsFinalVideo.mov

您应该使用appendingPathComponent()代替：

func createPath() -> URL {
    let paths = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)
    let documentDirectory = URL(fileURLWithPath: paths.first!)
    let url = documentDirectory.appendingPathComponent("FinalVideo.mov")

    if FileManager.default.fileExists(atPath: url.path) {
        try? FileManager.default.removeItem(at: url)
    }

    return url
}

Answer 2

您必须使用默认方法：appendingPathComponent()