How a Button Highlight Marker Affects the Subtitle Stream
If a subtitle already exists between the two markers that specify the start and end of a
button over video subtitle, its duration changes to match the time between the two
markers. This is true of all subtitle streams. If you have traditional subtitles on one or more
of the other subtitle streams, adding button highlight markers will also affect them. For
this reason, you must use care when deciding when and how long to have the buttons
over video subtitle appear, so as not to affect existing subtitles.
You can have several subtitle streams in the same track configured for buttons over video.
For example, you may be using text for the buttons and want to have different streams
for each language. It’s important to keep in mind that all button active areas, connections,
navigation settings, and color mapping settings are applied to all subtitle streams. The
only element that can be different between the streams is the text or overlay you use.