问录制视频上的iPhone水印。

EN

Error Domain=AVFoundationErrorDomain Code=-11841 "Operation Stopped" UserInfo={NSLocalizedFailureReason=The video could not be composed., NSLocalizedDescription=Operation Stopped, NSUnderlyingError=0x2830559b0 {Error Domain=NSOSStatusErrorDomain Code=-17390 "(null)"}}

    static func addSketchLayer(url: URL, sketchLayer: CALayer, block: @escaping (Result<URL, VideoExportError>) -> Void) {
        let composition = AVMutableComposition()
        let vidAsset = AVURLAsset(url: url)
        
        let videoTrack = vidAsset.tracks(withMediaType: AVMediaType.video)[0]
        let duration = vidAsset.duration
        let vid_timerange = CMTimeRangeMake(start: CMTime.zero, duration: duration)
        
        let videoRect = CGRect(origin: .zero, size: videoTrack.naturalSize)
        let transformedVideoRect = videoRect.applying(videoTrack.preferredTransform)
        let size = transformedVideoRect.size
                
        let compositionvideoTrack:AVMutableCompositionTrack = composition.addMutableTrack(withMediaType: AVMediaType.video, preferredTrackID: CMPersistentTrackID(kCMPersistentTrackID_Invalid))!
        
        try? compositionvideoTrack.insertTimeRange(vid_timerange, of: videoTrack, at: CMTime.zero)
        compositionvideoTrack.preferredTransform = videoTrack.preferredTransform
        
        let videolayer = CALayer()
        videolayer.frame = CGRect(x: 0, y: 0, width: size.width, height: size.height)
        videolayer.opacity = 1.0
        sketchLayer.contentsScale = 1
        
        let parentlayer = CALayer()
        parentlayer.frame = CGRect(x: 0, y: 0, width: size.width, height: size.height)
        sketchLayer.frame = CGRect(x: 0, y: 0, width: size.width, height: size.height)
        parentlayer.addSublayer(videolayer)
        parentlayer.addSublayer(sketchLayer)
        
        let layercomposition = AVMutableVideoComposition()
        layercomposition.frameDuration = CMTimeMake(value: 1, timescale: 30)
        layercomposition.renderScale = 1.0
        layercomposition.renderSize = CGSize(width: size.width, height: size.height)

        layercomposition.animationTool = AVVideoCompositionCoreAnimationTool(postProcessingAsVideoLayers: [videolayer], in: parentlayer)
        
        let instruction = AVMutableVideoCompositionInstruction()
        instruction.timeRange = CMTimeRangeMake(start: CMTime.zero, duration: composition.duration)
        let layerinstruction = AVMutableVideoCompositionLayerInstruction(assetTrack: compositionvideoTrack)
        layerinstruction.setTransform(compositionvideoTrack.preferredTransform, at: CMTime.zero)
        instruction.layerInstructions = [layerinstruction] as [AVVideoCompositionLayerInstruction]
        layercomposition.instructions = [instruction] as [AVVideoCompositionInstructionProtocol]
        
        let compositionAudioTrack:AVMutableCompositionTrack? = composition.addMutableTrack(withMediaType: AVMediaType.audio, preferredTrackID: CMPersistentTrackID(kCMPersistentTrackID_Invalid))
        let audioTracks = vidAsset.tracks(withMediaType: AVMediaType.audio)
        for audioTrack in audioTracks {
            try? compositionAudioTrack?.insertTimeRange(audioTrack.timeRange, of: audioTrack, at: CMTime.zero)
        }
        
        let movieDestinationUrl = URL(fileURLWithPath: NSTemporaryDirectory() + "/exported.mp4")
        try? FileManager().removeItem(at: movieDestinationUrl)
        
        let assetExport = AVAssetExportSession(asset: composition, presetName:AVAssetExportPresetHighestQuality)!
        assetExport.outputFileType = AVFileType.mp4
        assetExport.outputURL = movieDestinationUrl
        assetExport.videoComposition = layercomposition
        
        assetExport.exportAsynchronously(completionHandler: {
            switch assetExport.status {
            case AVAssetExportSessionStatus.failed:
                print(assetExport.error ?? "unknown error")
                block(.failure(.failed))
            case AVAssetExportSessionStatus.cancelled:
                print(assetExport.error ?? "unknown error")
                block(.failure(.canceled))
            default:
                block(.success(movieDestinationUrl))
            }
        })
    }

enum VideoExportError: Error {
    case failed
    case canceled
}