AVMutableComposition调整大小问题 [英] AVMutableComposition resizing issue

问题描述

我正在尝试使用AVMutableComposition将图像渲染为由前置摄像头捕获的视频.生成的视频(包括图像)的大小非常合适.

I'm trying to render an image into a video captured with the front camera using AVMutableComposition. The size of the resulting video (including the image) is perfectly fine.

但是，初始视频的大小将如下图所示:

However, the initial video will be resized as shown in this picture:

我正在使用 NextLevelSessionExporter ，这是我的代码段:

I'm using the NextLevelSessionExporter and this is my code snippet:

// * MARK - Creating composition
        /// Create AVMutableComposition object. This object will hold the AVMutableCompositionTrack instances.
        let mainMutableComposition = AVMutableComposition()

        /// Creating an empty video track
        let videoTrack = mainMutableComposition.addMutableTrack(withMediaType: AVMediaType.video, preferredTrackID: kCMPersistentTrackID_Invalid)
        let videoAssetTrack = videoAsset.tracks(withMediaType: AVMediaType.video)[0]

        do {
            //Adding the video track
            try videoTrack?.insertTimeRange(CMTimeRange(start: kCMTimeZero, duration: videoAsset.duration), of: videoAsset.tracks(withMediaType: AVMediaType.video).first!, at: kCMTimeZero)

        } catch {
            completion(false,  nil)
        }

        /// Adding audio if user wants to.
        if withAudio {
            do {
                //Adding the video track
                let audio = videoAsset.tracks(withMediaType: AVMediaType.audio).first
                if audio != nil {
                    let audioTrack = mainMutableComposition.addMutableTrack(withMediaType: AVMediaType.audio, preferredTrackID: kCMPersistentTrackID_Invalid)
                    try audioTrack?.insertTimeRange(CMTimeRange(start: kCMTimeZero, duration: videoAsset.duration), of: audio!, at: kCMTimeZero)

                }

            } catch {
                completion(false,  nil)
            }

        }

        // * MARK - Composition is ready ----------

        // Create AVMutableVideoCompositionInstruction
        let compositionInstructions = AVMutableVideoCompositionInstruction()
        compositionInstructions.timeRange = CMTimeRange(start: kCMTimeZero, duration: videoAsset.duration)

        // Create an AvmutableVideoCompositionLayerInstruction
        let videoLayerInstruction = AVMutableVideoCompositionLayerInstruction.init(assetTrack: videoTrack!)
        videoLayerInstruction.setTransform(videoAssetTrack.preferredTransform, at: kCMTimeZero)
        compositionInstructions.layerInstructions = [videoLayerInstruction]

        //Add instructions
        let videoComposition = AVMutableVideoComposition()

        let naturalSize : CGSize = videoAssetTrack.naturalSize

        ///Rendering image into video
        let renderWidth = naturalSize.width
        let renderHeight = naturalSize.height

        //Assigning instructions and rendering size
        videoComposition.renderSize = CGSize(width: renderWidth, height: renderHeight)
        videoComposition.instructions = [compositionInstructions]
        videoComposition.frameDuration = CMTime(value: 1, timescale: Int32((videoTrack?.nominalFrameRate)!))

        //Applying image to instruction
        self.applyVideoImage(to: videoComposition, withSize: naturalSize, image: image)

        // Getting the output path
        let documentsURL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first
        let outputPath = documentsURL?.appendingPathComponent("lastEditedVideo.mp4")
        if FileManager.default.fileExists(atPath: (outputPath?.path)!) {
            do {
                try FileManager.default.removeItem(atPath: (outputPath?.path)!)
            }
            catch {
                completion(false, nil)
            }
        }



        // Create exporter
        let exporter = NextLevelSessionExporter(withAsset: mainMutableComposition)
        exporter.outputURL = outputPath
        exporter.outputFileType = AVFileType.mp4
        exporter.videoComposition = videoComposition

        let compressionDict: [String: Any] = [
            AVVideoAverageBitRateKey: NSNumber(integerLiteral: 2300000),
            AVVideoProfileLevelKey: AVVideoProfileLevelH264BaselineAutoLevel as String
            ]

        exporter.videoOutputConfiguration = [
            AVVideoCodecKey: AVVideoCodecType.h264,
            AVVideoWidthKey: NSNumber(integerLiteral: Int(naturalSize.width)),
            AVVideoHeightKey: NSNumber(integerLiteral: Int(naturalSize.height)),
            AVVideoCompressionPropertiesKey: compressionDict
        ]

        exporter.audioOutputConfiguration = [
            AVFormatIDKey: kAudioFormatMPEG4AAC,
            AVEncoderBitRateKey: NSNumber(integerLiteral: 128000),
            AVNumberOfChannelsKey: NSNumber(integerLiteral: 2),
            AVSampleRateKey: NSNumber(value: Float(44100))
        ]

        completion(true, exporter)
    }

这是我的applyVideoImage()函数.

This is my applyVideoImage() function.

private func applyVideoImage(to composition: AVMutableVideoComposition, withSize size: CGSize, image: UIImage) { //Adds an image to a video composition

    //Creating image layer
    let overlayLayer = CALayer()
    let overlayImage: UIImage = image
    overlayLayer.contents = overlayImage.cgImage
    overlayLayer.frame = CGRect(x: 0, y: 0, width: size.width, height: size.height)
    overlayLayer.contentsGravity = kCAGravityResizeAspectFill
    overlayLayer.masksToBounds = true

    //Creating parent and video layer
    let parentLayer = CALayer()
    let videoLayer = CALayer()
    parentLayer.frame = CGRect(x: 0, y: 0, width: size.width, height: size.height)
    videoLayer.frame = CGRect(x: 0, y: 0, width: size.width, height: size.height)
    parentLayer.addSublayer(videoLayer)
    parentLayer.addSublayer(overlayLayer)

    //Adding those layers to video
    composition.animationTool = AVVideoCompositionCoreAnimationTool(postProcessingAsVideoLayer: videoLayer, in: parentLayer)
}

仅当我导出用前置摄像头捕获的镜像视频时，才会发生此错误.

EDIT 1: This bug only occurs when I'm exporting a mirrored video that has been captured with the front camera.

推荐答案

这确实很棘手:您需要检查视频轨道的preferredTransform以确定它是否是纵向视频.

This is really tricky: You need to check the preferredTransform of the video track to determine wether it is a portrait video or not.

    var videoAssetOrientation = UIImageOrientation.up
    var isVideoAssetPortrait = false
    var videoTransform = videoAssetTrack.preferredTransform
    if needsMirroring == true  {
        isVideoAssetPortrait = true
    }else if videoTransform.a == 0 && videoTransform.b == 1.0 && videoTransform.c == -1.0 && videoTransform.d == 0 {
        videoAssetOrientation = .right
        isVideoAssetPortrait = true
    }else if videoTransform.a == 0 && videoTransform.b == -1.0 && videoTransform.c == 1.0 && videoTransform.d == 0 {
        videoAssetOrientation = .left
        isVideoAssetPortrait = true
    }else if videoTransform.a == 1.0 && videoTransform.b == 0 && videoTransform.c == 0 && videoTransform.d == 1.0 {
        videoAssetOrientation = .up
    }else if videoTransform.a == -1.0 && videoTransform.b == 0 && videoTransform.c == 0 && videoTransform.d == -1.0 {
        videoAssetOrientation = .down
    }

    //Add instructions
    mainInstruction.layerInstructions = [videoLayerInstruction]
    let mainCompositionInst = AVMutableVideoComposition()
    let naturalSize : CGSize!
    if isVideoAssetPortrait {
        naturalSize = CGSize(width: videoAssetTrack.naturalSize.height, height: videoAssetTrack.naturalSize.width)
    } else {
        naturalSize = videoAssetTrack.naturalSize
    }

希望有帮助.

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