ManagedMediaSource Support

[robwalch]

This PR will...

1. Use ManagedMediaSource (MMS) when available rather than MediaSource for MSE based playback
   • Adds preferManagedMediaSource config option which defaults to true. Set to false to use standard MediaSource when available even if MMS is present.
2. Start and stop loading of media segments with MMS "startstreaming" and "endstreaming" events
   • Adds new new player API methods pauseBuffering() and resumeBuffering()
     (unlike startLoad() and stopLoad(), these methods do not interrupt Playlist loading)
3. Cap max quality based on MMS quality:
   1. low = ABR selection limited to 1280x720p max
   2. medium = 1920x1080p max
   3. (other) = no limit
4. Use HTMLSourceElements for MediaSource blob URL and set media.disableRemotePlayback to true to allow ManagedMediaSource to open (users can add additional source elements and allow remote playback as needed).
   • Setting preferManagedMediaSource to false prevents this behavior

Why is this Pull Request needed?

Using ManagedMediaSource when available allows the User Agent to manage buffer levels and limit quality based on information not available to the page.

Are there any points in the code the reviewer needs to double check?

ManagedMediaSource explainer: w3c/media-source#320

[RealAlphabet]

Is the API already available on Webkit ?

[jyavenard]

it is available on Safari 17 and iPadOS 17 beta

[robwalch]

We could also test for WebKitPlaybackTargetAvailabilityEvent here before bothering to use source elements.

[JuanMorenoS]

Hi! TY so much for sharing this PR.
I'm testing that on iOS 17 (xcode emulator) and is not working.
I commented this line in order to force HLS.JS (maybe that logic is missing in the PR)

If you need help to finish this PR please let me know!

[robwalch]

Hi @JuanMorenoS,

ManagedMediaSource needs to be enabled via Settings > Safari > Advanced > Feature Flags > Managed Media Source API.

There is a known issue in iOS 17 beta 5 preventing the isTypeSupported check from passing. The library can not operate without passing isTypeSupported checks. Until there is a fix, you can test in Safari Technology Preview, or try iPad.

[adityapatadia]

More details available in this nice video: https://developer.apple.com/videos/play/wwdc2023/10122/

[JuanMorenoS]

Hi @robwalch ,

I was wondering if you've heard any updates about the issue in iOS 17? It's been released, but I'm still having trouble playing content with HLS.JS. Any help would be appreciated

[jyavenard]

It will be available in iOS 17.1 beta 2

[matamatanot]

🎉

https://webkit.org/blog/14735/webkit-features-in-safari-17-1/