[Feature Request] Add initial audio codec support

[KunXi-Fox]

Context

Currently rx-player use the first audio codec as default audio codec:

rx-player/src/core/stream/period/period_stream.ts

Lines 472 to 485 in 7b24c52

	function getFirstDeclaredMimeType(adaptation: IAdaptation): string {
	const representations = adaptation.representations.filter(
	(r) => r.isPlayable() !== false,
	);
	if (representations.length === 0) {
	const noRepErr = new MediaError(
	"NO_PLAYABLE_REPRESENTATION",
	"No Representation in the chosen " + adaptation.type + " Adaptation can be played",
	{ tracks: [toTaggedTrack(adaptation)] },
	);
	throw noRepErr;
	}
	return representations[0].getMimeTypeString();
	}

If I want to use another audio codec based on user preferences, I need to manually call setAudioTrack method. This is works at most of cases except the device that not support seamless audio codec switch, which means every audio codec changes will lead to a reload.

Solution

Provide a initialAudioCodec option and change getFirstDeclaredMimeType method to based on initialAudioCodec, if no initialAudioCodec specified, then fallback to first available audio codec.

[peaBerberian]

Hi @KunXi-Fox,

Normally you can set the audio track based on codecs before the RxPlayer has made any choice (and thus not have a reload) by reacting to the newAvailablePeriods event. For example:

player.addEventListener("newAvailablePeriods", (periods) => {
  for (const period of periods) {
    const audioTracks = player.getAvailableAudioTracks(period.id);
    
    // use external logic to select the wanted audio track based on the codec
    const chosenAudioTrack = chooseAudioTrack(audioTracks);

    if (chosenAudioTrack) {
      player.setAudioTrack({
        periodId: period.id,
        trackId: chosenAudioTrack.id,
      });
    }
  }
});

https://developers.canal-plus.com/rx-player/doc/api/Track_Selection/setAudioTrack.html#setting-the-audio-track-as-soon-as-possible
https://developers.canal-plus.com/rx-player/doc/api/Player_Events.html#newavailableperiods

At what point do you update the audio track? If it's e.g. at the "LOADED" state it may be late because the RxPlayer already has loaded audio data (from the previous track).

[KunXi-Fox]

Yeah, just as you said, I set the initial audio codec at LOADED state. I'll try set it when first newAvailablePeriods event fired and see if it solve the problem.