Determine size/aspect ratio of video for SKVideoNode in SceneKit

How can I get the video size of a video from AVPlayer to set the geometry size of my node?

For example, I have an SCNPlane with a width and height

let planeGeo = SCNPlane(width: 5, height: 5)

So now I instantiate my video player

let videoURL = NSURL(string: someURL)
let player = AVPlayer(URL: videoURL!)

and my SKVideoNode

let spriteKitScene = SKScene(size: CGSize(width: 1920, height: 1080))
spriteKitScene.scaleMode = .AspectFit

videoSpriteKitNode = SKVideoNode(AVPlayer: player)
videoSpriteKitNode.anchorPoint = CGPointMake(0,0)
videoSpriteKitNode.size.width = spriteKitScene.size.width
videoSpriteKitNode.size.height = spriteKitScene.size.height

spriteKitScene.addChild(videoSpriteKitNode)

planeGeo!.firstMaterial.diffuse.contents = spriteKitScene
videoSpriteKitNode.play()

So now I want to have the video size to resize my plane to a correct aspect ratio. I already fiddled around with AVLPlayerLayer but this gives me always 0

let avLayer = AVPlayerLayer(player: player)
print(avLayer.videoRect.width) //0
print(avLayer.videoRect.height) //0

Also I tried that here but it doesn't work as well

let avLayer = AVPlayerLayer(player: player)
let layer = avLayer.sublayers![0]
let transformedBounds = CGRectApplyAffineTransform(layer.bounds, CATransform3DGetAffineTransform(layer.sublayerTransform))
print(transformedBounds.width) //0
print(transformedBounds.height) //0

Ok I figured it out, KVO is the way to go. Add in viewDidLoad:

player.currentItem?.addObserver(self, forKeyPath: "presentationSize", options: .New, context: nil)

in deinit:

player.currentItem?.removeObserver(self, forKeyPath: "presentationSize")

and then add:

override func observeValueForKeyPath(keyPath: String?, ofObject object: AnyObject?, change: [String : AnyObject]?, context: UnsafeMutablePointer<Void>) {
    
    if keyPath == "presentationSize" {
        if let item = object as? AVPlayerItem {
            let size = item.presentationSize
            let width = size.width
            let height = size.height

            //Set size of geometry here
        }
    }
}

Typical code for 2022 syntax:

var py: AVPlayer?
private var pyContext = 0
...

guard let url = URL(string: "https:// .. /test.m4v") else { return }
py = AVPlayer(url: url)
someNode.geometry?.firstMaterial?.diffuse.contents = py

py?.currentItem?.addObserver(self,
   forKeyPath: "presentationSize",
   context: &pyContext)    
...

override func observeValue(forKeyPath keyPath: String?,
                           of object: Any?,
                           change: [NSKeyValueChangeKey : Any]?,
                           context: UnsafeMutableRawPointer?) {

    if context == &py1Context && keyPath == "presentationSize" {
        print("Found it ...")

        guard let item = object as AVPlayerItem else { return }

        let ps = item.presentationSize
        let aspect: Float = Float(ps.width) / Float(ps.height)
        someNode.geometry?.firstMaterial?
           .diffuse.contentsTransform =
           SCNMatrix4MakeScale( .. , .. , 1)
    }
}

Addendum. Calculating the correct scaling is tricky

Unfortunately any time you work with video, if the exact size of the streaming content is not always the same, then shaping the video is a huge pain. Of course you have many considerations like whether letterboxed, etc etc. In some simple cases the calculation looks like this:

// 1. You nave finally received the info on the video from the HLS stream:

let ps = item.presentationSize
let spect: Float = Float(ps.width) / Float(ps.height)

// 2. Over in your 3D code, you need to know the current facts on the mesh:

let planeW = ... width of your mesh
let planeH = ... height of your mesh
let planeAspect = planeW / planeH

It's possible you are using Apple's simple provided flat square mesh, such as

var simplePlane = SCNPlane()
simplePlane.width = 2.783
simplePlane.height = 1.8723

One way or another you need the w/h of your mesh. And then,

// 3. In many (not all) cases, the solution is:

let final = vidAspect / planeAspect
print("we'll try this: \(final)")
yourNode.geometry?
  .firstMaterial?.diffuse
  .contentsTransform = SCNMatrix4MakeScale(1.0, final, 1.0)