Delivering-Intuitive-Media-Playback-with-AVKit.md

Delivering Intuitive Media Playback with AVKit

📅 2020.6.4 (THU)

🗂 WWDC2019 | Session : 503 | Category : AVKit

🔗 https://developer.apple.com/videos/play/wwdc2019/503/

🔖 AVKit is a high-level framework for building media user interfaces, complete with playback controls, chapter navigation, Picture-in-Picture, audio routing, support for subtitles and closed captioning, Siri and Now Playing integration, and support for keyboard, Touch Bar, and remote control. Learn best practices in how to integrate these technologies into your own apps on iOS, tvOS, and iPad apps on Mac.

AVKit in the Stack

Media Playback with AVPlayerViewController on iOS and tvOS

import AVKit

// 1) Create an AVPlayer
let player = AVPlayer(url: "http://my.example/video.m3u8")

// 2) Create an AVPlayerViewController
let playerViewController = AVPlayerViewController()
playerViewController.player = player

// 3) Show it
present(playerViewController, animated: true)

Media playback with AVKit

When you use AVKit, you own the media playback objects. You are in control of creating and managing them.

And video rendering is build in on top of same core technology that powers AVPlayerLayer.

AVPlayerViewController on iOS

🆕 Full screen callbacks

• Extends AVPlayerViewControllerDelegate

• Notifies delegate when beginning or ending full screen presentation

  @available(iOS 12.0, *)
  
  func playerViewController(_ playerViewController: AVPlayerViewController, 
  				willBeginFullScreenPresentationWithAnimationCoordinator coordinator: 
  				UIViewControllerTransitionCoordinator)
  
  func playerViewController(_ playerViewController: AVPlayerViewController, 
  				willEndFullScreenPresentationWithAnimationCoordinator coordinator: 
  				UIViewControllerTransitionCoordinator)

Implementing AVPlayerControllerDelegate's full screen callbacks

fund playerViewController(_ playerViewController: AVPlayerViewController, 
				willBeginFullScreenPresentationWithAnimationCoordinator coordinator: 
				UIViewControllerTransitionCoordinator) {
	coordinator.animate(alongsideTransition: { (context) in
		// Add coordinated animations
	)} { (context) in
		if context.isCancelled {
			// Still embedded inline
		} else {
			// Presented full screen
			// Take strong reference to playerViewControllelr if needed
		}
}

alongsideTransition calback

→ This is where you find out whether a transition succeeded or whether the user cancelled. This is the source of truth for learning about entering full screen from an inline presentation.

🆕 Full Screen Callbacks

Retargeting dismissal animaion

• Keep embedded playerViewController alive when full screen

  • Deallocating will stop full screen playback
  • Okay to be offscreen or removed from superview / parent

• Use delegate to restore playerViewController or retarget animation

  func playerViewController(_ playerViewController: AVPlayerViewController, 
  				willEndFullScreenPresentationWithAnimationCoordinator coordinator: 
  				UIViewControllerTransitionCoordinator) {
  	// If scrolled away, update playerViewController's layout here
  }

• Track full screen presentation state with AVPlayerViewControllerDelegate

  • Do not rely on viewWillAppear(_:) and friends

• Works for both embedded and full screen presentations

🆕 AVPlayerViewController in iPad Apps on the Mac

You get the same UI that you expect from Apple's playback UIs with all the functionality that AVPlayerController delivers for iPad apps.

But you also get some platform specific features for Mac. (touch bar support, keyboard support, picture-in-picture support)

→ How many new lines of code? 0!

• Exact same API an os iOS
• Picture-in-picture support
  • Includes AVPictureInPictureController (also for AppKit)
  • And AVPlayerView, for AppKit-based apps
• Touch Bar, keyboard, and Now Playing support
• Audio and AirPlay routing
• Available in macOS 10.15

🆕 External Metadata

🆕 Improved Support For Custom Controls

• Interactive dismissals
• Landscape support for portrait-only apps
• Keyboard and Touch Bar support
• Now Playing management
• Automatic video zoom

🆕 Custom Playback Controls

• Set showsPlaybackControls to false
• Present modally
• Add controls to contentOverlayView
• For the best user experience, you should:
  • Override UIViewController methods for status bar, home inidicator
  • Pass unhandled touches through your view
  • Let AVKit handle double-tap for video zoom

Best practices

Showing Full Screen

• Covers UIWindowScene coordinate space
• Use cases:
  • Splash screen
  • Full screen playback

Splash Screen

UIViewController containment API

• Add as child:

  parent.addChild(playerViewController)
  parent.view.addSubView(playerViewControler.view) // Or other UIView insertion API
  //Enable auto layout and set up constraints
  playerViewController.didMove(toParent: parent)

• Remove from parent:

  playerViewController.willMove(toParent: nil)
  playerViewControoler.view.removeFromSuperview()
  playerViewController.removeFromParent()

Configure AVPlayerViewController

• Disable playback controls:

  playerViewController.showsPlyabackControls = false

• Make video fill entire screen:

  playerViewController.videoGravity = .resizeAspectFill

• Set background color (if needed):

  playerViewController.view.backgroundColor = .clear

AVFoundation best practices

• Disable AVPlayer.allowsExternalPlayback
• Configure AVAudioSession for secondary media playback
  • Use .ambient category
• Observe AVAudioSession.silenceSecondaryAudioHintNotification
  • Honor AVAudioSession.secondaryAudioShouldBeSilencedHint

Full Screen Playback

AVPlayerViewController best practices

• Present modally (not as childViewController of other ViewController)

• Use the default modalPresentationStyle

• Do not set AVPlayerViewController.videoGravity

• Use AVPlayerViewController to track full screen presentation state

  • Do not rely on viewWillAppear(:_) and friends

• Set up AVPlayerItem before buffering

  • Set AVPlayer.rate for setting item

• Observe AVPlayer.status and AVPlayerItem.status

  • Don't begin playback until status is .readyToPlay
  • Check error property when status is .failed
    • Rebuild AVFoundation objects if .mediaServicesWereReset

• Enable AVPlayer.usesExternalPlaybackWhileExternalScreenIsActive

• Configure AVAudioSession for .playback

Embedding AVPlayerViewController InLine

Showing poster images

• Use .contentOverlayView
  • Okay to use before setting player or player item
• Observe .isReadyForDisplay
  • Returns true when first frame is ready

let token = pvc.observe(\.isReadyForDisplay, options: [.initil]) {
								[weak self] observed, _ in
	if observed.isReadyForDisplay {
		// Hide any poster frame or placeholder
	}
}

Picture-in-picture

Continue playing when entering background. If you must pause, wail until in background

Restoring from picture-in-picture using AVPlayerViewControllerDelegate

func playerViewController(
		_ playerViewController: AVPlayerViewController,
		restoreUserInterfaceForPictureInPictureStopWithCompletionHandler
		completionHandler: @escaping (Bool) -> Void) {
	presentingViewController.present(playerViewController, animated: true) {
		// Must invoke completionHandler
		completionHandler(true)
	}
}

---

What AVPlayerViewController Provides on tvOS

🆕Custom interactive overlays

Set the customOverlayViewController property of the playerViewController

let customInteractiveVideoOverlay = UIViewController(nibName: "CustomInteractiveVideoOverlay", bundle: nil)
newPlayerViewController.customOverayViewController = customInteractiveVideoOverlay

🆕 Live broadcast channel-flipping

• For live streams
• Swipe horizontally for next / previous channels
• Channel interstitial screen describes a channel with it loads

🆕 Parental content restriction enforcement

Best Practices on tvOS

• Controls revealed by swipe-up? Use a custom overlay instead
• Use the delegate dismissal notifications rather than a UITapGestureRecognizer
• Avoid toggling showPlaybackControls during presentation
• Provide media content ratings
• Test with parental content restrictions enabled