Flip video horizontally if so it does not have mirror effect

Question

In my custom camera, when I film a video with the front facing camera, it does the mirror effect like the original iPhone camera. I don't want that. I would like to flip the video horizontally, and implement that in this function down below. I have a boolean variable called filmedWithFront that is true when a video is filmed with the front facing camera.

var filmedWithFront = false

func cropVideo(_ outputFileURL:URL){
    let videoAsset: AVAsset = AVAsset(url: outputFileURL) as AVAsset

    let clipVideoTrack = videoAsset.tracks(withMediaType: AVMediaType.video).first! as AVAssetTrack

    let composition = AVMutableComposition()
    composition.addMutableTrack(withMediaType: AVMediaType.video, preferredTrackID: CMPersistentTrackID())

    let videoComposition = AVMutableVideoComposition()

    videoComposition.renderSize = CGSize(width: 720, height: 1280)

    videoComposition.frameDuration = CMTimeMake(1, 30)

    let instruction = AVMutableVideoCompositionInstruction()

    instruction.timeRange = CMTimeRangeMake(kCMTimeZero, CMTimeMakeWithSeconds(180, 30))

    // rotate to portrait
    let transformer:AVMutableVideoCompositionLayerInstruction = AVMutableVideoCompositionLayerInstruction(assetTrack: clipVideoTrack)
    let t1 = CGAffineTransform(translationX: 720, y: 0);
    let t2 = t1.rotated(by: CGFloat(CGFloat.pi/2));

    transformer.setTransform(t2, at: kCMTimeZero)
    instruction.layerInstructions = [transformer]
    videoComposition.instructions = [instruction]


    if filmedWithFront == true {
        // This is where I want to add the code to flip video horizontally
    }


    let removedPath = outputFileURL.path
    let documentsPath = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0] as NSString
    let cropUniqueId = NSUUID().uuidString
    let outputPath = "\(documentsPath)/\(cropUniqueId).mov"

    arrayOfStringPaths.append(outputPath)
    stringOfArrayPaths = outputPath
    let relativePath = "\(cropUniqueId).mov"
    let relativeURL = URL(fileURLWithPath: relativePath)
    saveData(arrayPath: relativePath)
    let outputUrl = URL(fileURLWithPath: outputPath, relativeTo: relativeURL)
    let exporter = AVAssetExportSession(asset: videoAsset, presetName: AVAssetExportPreset1280x720)!

    exporter.videoComposition = videoComposition
    exporter.outputURL = outputUrl
    exporter.outputFileType = AVFileType.mov
    exporter.shouldOptimizeForNetworkUse = true

    exporter.exportAsynchronously(completionHandler: { () -> Void in
        DispatchQueue.main.async(execute: {
            self.handleExportCompletion(exporter, removedPath)
        })
    })
}

Answer 1

Here's a snippet of the transform I did to finally fix mirrored video output from front camera... videoInputWriter is AVAssetWriterInput. Hope this helps.

if (cameraPosition == .front) {
    var transform: CGAffineTransform = CGAffineTransform(scaleX: -1.0, y: 1.0)
    transform = transform.rotated(by: CGFloat(Double.pi/2))
    self.videoInputWriter.transform = transform
}