I have a ProRes 4444 format video with an alpha channel.
The circle in the middle of the video is completely opaque, while the rest is fully transparent. Everything looks normal in iMovie, as I can see the background through the surrounding parts.
However, when I play it using AVPlayer, the parts that are supposed to be fully transparent appear somewhat opaque, as shown in the image below:
I used the official project provided by Apple named 'using_hevc_video_with_alpha', but I only replaced the HEVC with alpha format file with a ProRes 4444 format video file. Below is the main code.
import Cocoa
import SpriteKit
import AVFoundation
class ViewController: NSViewController {
@IBOutlet var skView: SKView!
var videoPlayer: AVPlayer!
override func viewDidLoad() {
super.viewDidLoad()
if let view = self.skView {
// Load the SKScene from 'backgroundScene.sks'
guard let scene = SKScene(fileNamed: "backgroundScene") else {
print ("Could not create a background scene")
return
}
// Set the scale mode to scale to fit the window
scene.scaleMode = .aspectFill
// Present the scene
view.presentScene(scene)
// Add the video node
guard let alphaMovieURL = Bundle.main.url(forResource: "xuewang", withExtension: "mov") else {
print("Failed to overlay alpha movie on the background")
return
}
videoPlayer = AVPlayer(url: alphaMovieURL)
let video = SKVideoNode(avPlayer: videoPlayer)
video.size = CGSize(width: view.frame.width, height: view.frame.height)
print( "Video size is %f x %f", video.size.width, video.size.height)
scene.addChild(video)
// Play video
videoPlayer.play()
}
}
}