fix(safari): video not starting because key are never considered usable for a track

[Florent-Bouisset]

We observed an issue with encrypted HLS playlist on Safari with the legacy EME API:
If the HLS playlist has multiple audio with the same encryption key, and the default lang of the playlist is NOT the lang of the OS, the video will stall.

This appears to be a race condition within Safari, that occurs when the licence is received at about the same time the audio tracks are added.

Safari will continuously fire events "webkitneedkey" for the init-data we just processed, the RxPlayer will not be re-creating a session for an already handled init-data.
Forcing to recreate a session even if the init-data is already handled fixed the issue.

video.addEventListener("webkitneedkey", onEncrypted);

function onEncrypted(event) {
   const video = event.target;

   // check if initData is already processed
   if(alreadyProcessed(initData)) {
      // don't re-create a session, there is already an active session
      // with this init-data
      return 
   }

   // create a session
   ...
   const session = video.webkitKeys.createSession("video/mp4", initData)

   // perform the licence request
   ...
}

[Florent-Bouisset]

Maybe related to issue #1326

[peaBerberian]

To propose an alternative solution for this one: Maybe we could add something to the payload when receiving the event, like a forceSessionCreation boolean attribute for example where a MediaKeySession would be re-created?

Also maybe when doing this we should close the previous MediaKeySession or at least close it. I'm afraid that we could be mixing things up if we had two alive MediaKeySession linked to the same key id + init data.

[peaBerberian]

We may want to better type onEncrypted instead?

[peaBerberian]

Is that still necessary if we update onEncrypted's type in IEmeApiImplementation like this?:

  onEncrypted: (
    target: IEventTargetLike,
    listener: (evt: ICustomMediaEncryptedEvent) => void,
    cancelSignal: CancellationSignal,
  ) => void;

[Florent-Bouisset]

Yes because createCompatibleEventListener returns a listener of type (event?: Event) => void
and will not satisfies type (evt: ICustomMediaEncryptedEvent) => void

[peaBerberian]

Event should be compatible to an ICustomMediaEncryptedEvent though as forceSessionRecreation is optional no?

[peaBerberian]

Yet maybe Event is not compatible with a MediaEncryptedEvent, in which case we might improve on the type?
Through createCompatibleEventListener event overloading?

[peaBerberian]

Also, does it work?

[peaBerberian]

Weird that eslint is not telling us about this weird function naming