Function av_subtitle_to_subtitle_frame 

pub unsafe fn av_subtitle_to_subtitle_frame(
    av_subtitle: *const AVSubtitle,
    time_base: Timebase,
) -> Result<SubtitleFrame<SubtitleFrameExtra, FfmpegBuffer>, ConvertError>

[av_subtitle_to_subtitle_frame_as] on the view lane.

Safety

As the crate-private worker: a live source for the duration of the call, and — on this lane — no handle capable of mutating its buffers may outlive the returned carriers.