Fix flickering/blinking IMSC Subtitles#4359

Merged

dsilhavy merged 5 commits intoDash-Industry-Forum:developmentfrom mattjuggins:font-flickering-fix

Jan 18, 2024

+54-18

Commits on Jan 11, 2024

Commits on Jan 12, 2024

Make sure to not effect CEA608 subs, and add comments for clarity
mattjuggins
committed

Commits on Jan 16, 2024

Address PR comments
mattjuggins
committed