使用 AVAssetExportSession 全屏导出视频

Posted 2023-03-12

【中文标题】使用 AVAssetExportSession 全屏导出视频

【英文标题】：Exporting Video in full screen with AVAssetExportSession

【发布时间】：2017-05-09 15:07:16

【问题描述】：

我正在尝试为视频制作一些动画（录制后），然后将其导出。 但在任何动画之前，我遇到了方向变成横向的问题（没有导出它是纵向），但没有解决，但现在我无法让它全屏显示。在 iphone 6,7 加上它的全屏在 ipad 中如何不是。

这是我的方法：

func export(_ url : URL) 
    let composition = AVMutableComposition()
    let asset = AVURLAsset(url: url, options: nil)

    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)
     catch 
        print(error)
    

    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 = self.view.bounds.size

    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)

    let layercomposition = AVMutableVideoComposition()
    layercomposition.frameDuration = CMTimeMake(1, 30)
    layercomposition.renderSize = self.view.bounds.size
    layercomposition.animationTool = AVVideoCompositionCoreAnimationTool(postProcessingAsVideoLayer: videolayer, in: parentlayer)

    let instruction = AVMutableVideoCompositionInstruction()

    instruction.timeRange = CMTimeRangeMake(kCMTimeZero, asset.duration)

    let videotrack = composition.tracks(withMediaType: AVMediaTypeVideo)[0] as AVAssetTrack
    let layerinstruction = AVMutableVideoCompositionLayerInstruction(assetTrack: videotrack)


    let ratio = size.height / videoTrack.naturalSize.width

    composition.naturalSize = videoTrack.naturalSize

    layerinstruction.setTransform(videoTrack.preferredTransform.scaledBy(x: 0.645 , y: ratio).translatedBy(x: self.view.bounds.height, y: 0), at: kCMTimeZero)

    instruction.layerInstructions = [layerinstruction]
    layercomposition.instructions = [instruction]

    let filePath = self.fileName()
    let movieUrl = URL(fileURLWithPath: filePath)

    guard let assetExport = AVAssetExportSession(asset: composition, presetName:AVAssetExportPresetHighestQuality) else return
    assetExport.videoComposition = layercomposition
    assetExport.outputFileType = AVFileTypeMPEG4
    assetExport.outputURL = movieUrl
    assetExport.exportAsynchronously(completionHandler: 
        switch assetExport.status 
        case .completed:
            print("success")
            let player = AVPlayer(url: movieUrl)
            let playerViewController = AVPlayerViewController()
            playerViewController.player = player
            self.present(playerViewController, animated: true) 
                playerViewController.player!.play()
            
            break
        case .cancelled:
            print("cancelled")
            break
        case .exporting:
            print("exporting")
            break
        case .failed:
            print("failed: \(String(describing: assetExport.error))")
            break
        case .unknown:
            print("unknown")
            break
        case .waiting:
            print("waiting")
            break
        
    )

【问题讨论】：

你试过AVAssetExportPreset以外的其他预设吗？

我认为这与您的layercomposition.renderSize 有关，您将其设置为当前视图，因此如果您在手机上运行此操作，iPad 上的输出视频会更小。你可以将renderSize设置为原始视频的大小吗？这可能会奏效。

也许这个比率是通过高度/宽度计算的：让 ratio = size.height / videoTrack.naturalSize.width

@Bluewings 是的，我的问题在于规模的计算

【参考方案1】：

解决我的问题的是更改比例因子和翻译量。这是下面的代码：

    let size = self.view.bounds.size
    let trackTransform = videoTrack.preferredTransform
    let xScale = size.height / videoTrack.naturalSize.width
    let yScale = size.width / videoTrack.naturalSize.height


    let exportTransform = videoTrack.preferredTransform.translatedBy(x: trackTransform.ty * -1 , y: 0).scaledBy(x: xScale , y: yScale)

【讨论】：

你在哪里插入 exportTransform ？