We've recently gone live with a feature that enables users to watch live content where subtitles were working as expected. However, once live several devices have transitioned to a firmware version of 9.2.0 which has caused subtitles to stop working for several streams.
We use dash feeds for live streaming, with the subtitle meta being embedded into the stream's manifest. Within the manifest we have a selection of two subtitle formats, the first being WebVTT and the later being TTML. On versions pre 9.2 WebVTT was always favoured, and this has been understood to work for all live streams, as well as VOD playback. However, with the update to 9.2, it would seem that TTML is being favoured instead.
We can confirm that the subtitles are being fetched successfully via Charles, and in code via the `availableSubtitleTracks` and `currentSubtitleTracks`. We've also tried setting the `subtitleTrack` via collecting the track name from the `availableSubtitleTracks` meta, but this didn't work either.
We do not have the option of deprecating TTML so that Roku would (we assume) return to favour WebVTT as there are other devices dependant on this.
So we were wondering if anybody has ran into a similar issue, perhaps with past firmware updates and what processes you took to resolve this?
Can you also try the "TrackName property is set to "webvtt/track" where track specifies the index of the caption track to render".
Also do you have a list of subtitles to select from in the manifest? I had issues with the list of subtitles in 9.1(subtitles wont load automatically, only on DASH VOD), had to limit the subtitles to one!
this is what I did for external subtitles to work, (if not reading from the manifest):
Thanks for getting back to us on this. Something about setting the trackName jogged our memory a bit, so what we did was review the availableTracks that were being registered behind the scenes, and collect the WebVTT trackName from here, and then pass this into the video content node to enforce this.