No, it’s not supported currently in the core playlist as I understand it.
The following are just some rough ideas:
Within the WPPlaylistView.playCurrentSrc() method, in the wp-playlist.js file, we have:
this.mejs.setSrc( this.playerNode.attr( 'src' ) );
This is currently only for a single source.
I checked the definition of srcSet() in MediaElment.js and found:
// This can be a url string
// or an array [{src:'file.mp4',type:'video/mp4'},{src:'file.webm',type:'video/webm'}]
setSrc: function (url) {
So it looks like there is a multiple file-type support in the MediaElment.js library.
Test ideas
If we had e.g. mp3 and ogg attributes, then the array might look like:
this.mejs.setSrc(
[
{ src:this.playerNode.attr( 'mp3' ), type:'audio/mp3'},
{ src:this.playerNode.attr( 'ogg' ), type:'audio/ogg'}
]
);
To test this we could have an ogg version for each mp3 media file in the playlist. Then we could add this array element:
src:this.playerNode.attr( 'src' ).replace( '.mp3', '.ogg' ), type:'audio/ogg'}
into the source array.
I’m not sure if one can override only the WPPlaylistView.playCurrentSrc() method or extend the WPPlaylistView Backbone view.
For testing one could e.g. dequeue the core wp-playlist.js file and enqueue a modified version instead.
Another approach might be to look for a way to adjust the player through the MediaElementPlayer object or with some other javascript workarounds.
Hope you can investigate this further 😉