Hi @edward.lee,
thanks for reaching out! The “loss” of the label is a known behaviour. We already track this internally and can update you here once we release a fix.
As a workaround, in the mean time, I would suggest you to try using a SubtitleLabeler, which is part of the LabelingConfig in the SourceConfig. (SourceConfig.labelingConfig.subtitleLabeler)
The SubtitleLabeler allows you to relabel all the subtitles of your Source.
In general the provided SubtitleTrack should be considered as a configuration. We try to apply the properties as possible, but there are other factors that might influence the resulting SubtitleTrack.
You are right, there is no further way to change the other properties directly.
I will take your findings to the ticket, so that we can have closer look.
Could you provide me some more information on your setup please. Are there already subtitle included in the base stream (SourceConfig.url) and what type of stream is it.
Ideally, you could share the stream URLs with us here or via support@bitmovin.com