Fragmented WebVTT and Sidecar WebVTT are displayed double in Chrome/Firefox, broken on Edge

[unifiedstreaming]

Environment

• [x] The MPD passes the DASH-IF Conformance Tool on http://dashif.org/conformance.html
• [x] The stream has correct Access-Control-Allow-Origin headers (CORS)
• [x] There are no network errors such as 404s in the browser console when trying to play the stream
• [x] The issue observed is not mentioned on https://github.com/Dash-Industry-Forum/dash.js/wiki/FAQ
• [x] The issue occurs in the latest reference client on http://reference.dashif.org/dash.js/ and not just on my page
• Link to playable MPD file: http://demo.unified-streaming.com/video/tears-of-steel/tears-of-steel-wvtt.ism/.mpd
• Dash.js version: 2.8.0
• Browser name/version: Edge, Chrome 64bit 67.0.3396.99, Firefox 64bit 60.0.2
• OS name/version: Windows 10 10.0.17134.112

Steps to reproduce

1. Please provide clear steps to reproduce your problem

Load http://reference.dashif.org/dash.js/v2.8.0/samples/dash-if-reference-player/index.html?mpd=http://demo.unified-streaming.com/video/tears-of-steel/tears-of-steel-wvtt.ism/.mpd

2. If the bug is intermittent, give a rough frequency if possible

Bug happens every time

Observed behaviour

Chrome and Firefox display same behavior. "de" subtitles chosen by default, which are displayed double. Selecting a different language shows the subtitle correctly.

For Edge, shows first subtitles then shows no subtitles past 0:25.

It seems that the player loads both sidecar wvtt files as well as the fragmented wvtt and breaks initialization.

Related issue: https://github.com/Dash-Industry-Forum/dash.js/issues/2529 still apparent in 2.8.0

[unifiedstreaming]

Hi @nicosang, the subtitles bugfix #2691 seems to have resolved the issue. Text no longer appears double for Chrome and Firefox, and Edge now plays back the subtitles correctly. Thanks for the fix!