dash stream not support uri started with // in baseUri field

I tried to show subtitle on dash stream, and it did showed there is available subtitle, but even after I turned caption on and selected track, subtitle still didn't show. 

After testing with dash.js library on web, it seems roku doesn't support url started with // in baseUrl field.

Is there any way to show subtitle with url like this?

Below is the stream I test:

Absolute url: http://testmpd.ddnsgeek.com:8080/out.mpd

Protocol-related url: http://testmpd.ddnsgeek.com:8080/out_protocol_relative.mpd