How to extract and remove closed captions
In analog TV broadcasting, closed captions look like subtitles but they are actually embedded inside the video stream. There is no subtitle stream assigned to them.
They are mainly intended for hearing-impaired people and are displayed as white text with black-box background.
Extract closed captions to a SRT file
This may be helpful when a translation to another language is needed.
ffmpeg -f lavfi -i "movie=INPUT.mp4[out0+subcc]" -map s "OUTPUT.srt"
Remove closed captions in SEI
This is achieved using the filter_units video bitstream filter.
ffmpeg -i "INPUT.mp4" -c copy -map 0 -bsf:v filter_units=remove_types=6 "OUTPUT.mp4"
for AVC and remove_types=39 for HEVC. MPEG does not have SEI, so that will not work.
Type SEI can have other information there, like HDR10+ metadata, so more accurate code is needed, see #5283.