Is bitmovin player supported baseUrl started with // in mpd file?

I try to show subtitle on a stream with protocol-related url on subtitle baseUrl field.

I have tried the below link on web, it works.
But on roku, No matter I used bitmovin player or native player, it only show available subtitle options, and subtitle didn’t show after selected it.

Do bitmovin player used same way to parse baseUrl?

absolute baseUrl:
protocol-related baseUrl:

This isn’t consistently supported across platforms. As the web is steadly moving to an HTTPS only world, and more and more platform features (like DRM) are only available on HTTPS sites, I’d recommend using HTTPS for your streams on all sites and apps.

Thank you for your reply.
It seems some platforms have not supported this feature,
so I resolve it by parsing mpd first, manually adding protocol(http,https) for each subtitle, and adding subtitles when setup the player.