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.