确定SKVideoNode在SceneKit中的视频大小/宽宽比

Question

如何从AVPlayer获得视频的视频大小来设置节点的几何大小？

例如，我有一个具有宽度和高度的SCNPlane

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

所以现在我实例化了我的视频播放器

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

还有我的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()

所以现在我想要视频大小来调整我的飞机的尺寸到一个正确的高宽比。我已经摆弄过AVLPlayerLayer了，但这总是给我0

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

我在这里也试过了，但效果不太好

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

Answer 1

好吧，我想出来了，KVO是你的出路。添加viewDidLoad：

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

在迪伊尼特：

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

然后添加：

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
        }
    }
}

2022语法的典型代码：

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)
    }
}

增编。计算正确的缩放是很困难的

不幸的是，任何时候处理视频时，如果流媒体内容的确切大小并不总是相同的话，那么视频的形成就会带来巨大的痛苦。当然，您有很多需要考虑的事项，如字母框等，，在一些简单的情况下，，计算如下：

// 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

您可能正在使用Apple提供的简单的平面方形网格，例如

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

无论如何，你都需要你的网格的w/h。然后,

// 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)

Answer 2

正如您注意到的，SKVideoNode size属性是在视频实际出现之后异步加载的，这可能需要一秒钟时间。如果有人需要同步解决方案，他们可能会尝试这样做。实例化一个AVURLAsset，您就可以访问具有naturalSize属性的视频轨道(AVAssetTrack)：

let videoURL = NSURL(string: someURL)!
let asset = AVURLAsset(url: videoURL)

let videoSize: CGSize
if let size = asset.tracks(withMediaType: .video).first?.naturalSize {
    videoSize = size
} else {
    // Handle error (shouldn't happen normally if the asset is
    // an actual video.)
    videoSize = .zero
}

let player = AVPlayer(item: AVPlayerItem(asset: asset))
// Alternatively:
// let player = AVPlayer(URL: videoURL!)

videoSpriteKitNode = SKVideoNode(AVPlayer: player)
// continue node setup...

Answer 3

如果您以前在使用videoNode.size编码时设置了skScene.size和skScene.size之间的相等，则可以使用SceneKit获得以积分表示的视频节点大小。有关详细信息，请阅读此帖子。

import SceneKit
import SpriteKit

let model = scene.rootNode.childNode(withName: "someNode", recursively: true)
    
let skScene = model?.geometry?.firstMaterial?.diffuse.contents as? SKScene
    
let skVideoNode = skScene?.children[0] as? SKVideoNode
    
guard let size = skVideoNode?.scene?.size,
      let position = skVideoNode?.position,
      let frame = skVideoNode?.frame
else { return }
    
print(String(format: "%.1f, %.1f", size.width, size.height))
print(position)
print(frame)
print(skVideoNode?.speed as Any)
print(skVideoNode?.description as Any)