I wish to parse the bitstream of HEVC video with alpha (specific video format reference WWDC2019: https://developer.apple.com/videos/play/wwdc2019/506). Taking the 'puppets_with_alpha_hevc.mov' file from 'Using HEVC Video with Alpha' as an example, I would first extract the HEVC bitstream, then parse its fields. When it comes to the VPS field, as I reach the vps_extension, I find that the bitstream in 'puppets_with_alpha_hevc.mov' does not conform to the HEVC standard document, preventing further parsing. Besides the 'HEVC Video with Alpha Interoperability Profile.pdf', are there any more detailed documents describing the HEVC video with alpha format? Also, is there anyone who can encode or decode HEVC with alpha videos on systems other than macOS?

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() } } }