我一天中的大部分时间都在围绕 StackOverflow 进行深入研究，虽然有很多关于该主题的精彩帖子，但我还没有找到解决我的问题的方法。 p>

我正在使用 AVAssetWriter 编写视频文件，没有问题。我的视频文件，如果我保存到我的相机胶卷，可以正确播放并按预期方向播放。以下是我的设置方式；

init(fileUrl:URL!, height:Int, width:Int) {

    // Setup the filter writer instance
    fileWriter = try? AVAssetWriter(outputURL: fileUrl, fileType: AVFileType.mov)

    // Setup the video settings
    let videoOutputSettings: Dictionary<String, AnyObject> = [
        AVVideoCodecKey : AVVideoCodecType.hevc as AnyObject,
        AVVideoWidthKey : width as AnyObject,
        AVVideoHeightKey : height as AnyObject
    ]

    // Setup the attributes dictionary
    let sourcePixelBufferAttributesDictionary = [
        String(kCVPixelBufferPixelFormatTypeKey) : Int(kCVPixelFormatType_32BGRA),
        String(kCVPixelBufferWidthKey) : Int(width),
        String(kCVPixelBufferHeightKey) : Int(height),
        String(kCVPixelFormatOpenGLESCompatibility) : kCFBooleanTrue
        ] as [String : Any]

    // Setup the video input
    videoInput = AVAssetWriterInput(mediaType: AVMediaType.video, outputSettings: videoOutputSettings)

    // Data should be expected in real time
    videoInput.expectsMediaDataInRealTime = true

    // Perform transform
    videoInput.transform = CGAffineTransform(rotationAngle: CGFloat(CGFloat.pi / 2.0))

    // Setup pixel buffer intput
    assetWriterPixelBufferInput = AVAssetWriterInputPixelBufferAdaptor(assetWriterInput: videoInput,
                                                                       sourcePixelBufferAttributes: sourcePixelBufferAttributesDictionary)

    // Add the input
    fileWriter.add(videoInput)
}

然后我想使用 AVMutableComposition 来保存应用了图像叠加层的视频，它可以正常工作，除了视频方向不正确；

func postProcessVideo(toFPS: Double, sourceVideo: URL, destination: URL, filterImage: UIImage?, completionHandler: @escaping (_ response: Bool) -> ()) {

    // Log
    print("Received call to begin post-processing video at:", sourceVideo)

    // Instantiate the AVMutableComposion
    let composition = AVMutableComposition()

    // Setup the video asset
    let vidAsset = AVURLAsset(url: sourceVideo, options: [:])

    // Get video track
    let vtrack = vidAsset.tracks(withMediaType: AVMediaType.video)

    // Setup the first video track as asset track
    let videoTrack: AVAssetTrack = vtrack[0]

    // Setup the video timerange
    let vid_timerange = CMTimeRangeMake(kCMTimeZero, vidAsset.duration)

    // Setup the composition video track
    let compositionvideoTrack:AVMutableCompositionTrack = composition.addMutableTrack(withMediaType: AVMediaType.video, preferredTrackID: CMPersistentTrackID())!

    // Insert expected time range
    do {
        try compositionvideoTrack.insertTimeRange(vid_timerange, of: videoTrack, at: kCMTimeZero)
    } catch {

    }

    // Setup the preferred transform
    compositionvideoTrack.preferredTransform = videoTrack.preferredTransform

    // Update time scale
    let finalTimeScale: Int64 = vidAsset.duration.value * 3

    // Adjust video track duration
    compositionvideoTrack.scaleTimeRange(CMTimeRangeMake(kCMTimeZero, vidAsset.duration), toDuration: CMTimeMake(finalTimeScale, vidAsset.duration.timescale))

    // Setup effect size
    let size = videoTrack.naturalSize

    // Setup the image
    let imglogo = UIImage(named: "gif1.png")
    let imglayer = CALayer()
    imglayer.contents = imglogo?.cgImage
    imglayer.frame = CGRect(x: 0, y: 0, width: size.width, height: size.height)
    imglayer.opacity = 0.0

    // Setup the video layer
    let videolayer = CALayer()

    // Setup the video layer frame
    videolayer.frame = CGRect(x: 0, y: 0, width: size.width, height: size.height)

    // Setup the parent layer
    let parentlayer = CALayer()

    // Setup the parent layer frame
    parentlayer.frame = CGRect(x: 0, y: 0, width: size.width, height: size.height)

    // Add video layer
    parentlayer.addSublayer(videolayer)

    // Add filter layer
    parentlayer.addSublayer(imglayer)

    // Setup the layer composition
    let layercomposition = AVMutableVideoComposition()

    // Setup the desired frame rate
    layercomposition.frameDuration = CMTimeMake(1, Int32(toFPS))

    // Setup the render size
    layercomposition.renderSize = size

    // Setup the animation tool
    layercomposition.animationTool = AVVideoCompositionCoreAnimationTool(postProcessingAsVideoLayer: videolayer, in: parentlayer)

    // Setup instruction for filter overlay
    let instruction = AVMutableVideoCompositionInstruction()

    // Setup the desired time range
    instruction.timeRange = CMTimeRangeMake(kCMTimeZero, composition.duration)

    // Setup video track
    let videotrack = composition.tracks(withMediaType: AVMediaType.video)[0]

    // Setup layer instruction
    let layerinstruction = AVMutableVideoCompositionLayerInstruction(assetTrack: videotrack)

    // Setup layer instructions
    instruction.layerInstructions = [layerinstruction]

    // Setup layer composition instructions
    layercomposition.instructions = [instruction]

    // Instantiate the asset export
    let assetExport = AVAssetExportSession(asset: composition, presetName:AVAssetExportPresetHighestQuality)

    // Setup the video composition
    assetExport?.videoComposition = layercomposition

    // Setup the output file type
    assetExport?.outputFileType = AVFileType.mov

    // Setup the destination
    assetExport?.outputURL = destination

    // Export video
    assetExport?.exportAsynchronously(completionHandler: {
        switch assetExport?.status{
        case .failed?:
            print("failed \(assetExport!.error)")
        case .cancelled?:
            print("cancelled \(assetExport!.error)")
        default:
            print("Movie complete")
            completionHandler(true)
        }
    })
}

很抱歉太长了，但是是否有任何突出的因素可以帮助解释导出过程中的方向变化？

谢谢!

最佳答案

我遇到了关于方向的问题，我是这样解决的:

AVMutableCompositionTrack *a_compositionVideoTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
[a_compositionVideoTrack setPreferredTransform:CGAffineTransformRotate(CGAffineTransformMakeScale(-1, 1), M_PI)];

通过旋转和缩放它。它是在 objective-C 中，但你可以很容易地转换它。你只需要改变这个:

// Setup the preferred transform
compositionvideoTrack.preferredTransform = videoTrack.preferredTransform

而不是 preferredTransform 手动给出转换。

关于ios - AVMutableComposition 没有正确定位视频，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/47745814/