Function subtitle_forces_burn_in 

pub fn subtitle_forces_burn_in(codec: &str) -> bool

Whether asking the server to serve this subtitle codec forces it to burn the subtitle into the picture.

Burn-in is not a subtitle cost — it is a video cost. It rules out remuxing the video stream, so a source we would otherwise have passed through untouched gets fully re-encoded frame by frame.

TRACES: UR-020 | DR-176 | UT-168