It depends on what sort of input file you're working with. In my case I had Final Cut Pro MOV Master files with a Scenarist (.scc) style eia-608 track. While ffmpeg can extract embeded closed captions from mpeg2 transport stream files, it can't deal with the eia-608 data on a separate track.
ccextractor should work out the box, but MOV revolves around Apple products and sometimes moves with complete disregard to third parties... as such you should normalize MOV files before dealing with them... a simple ffmpeg -i my.mov -c copy -map 0 out.mov should do the trick. Then CCExtractor's built in MP4Box build should be able to pass it the eia-track and decode it into something useable... like vtt.
Source: https://trac.ffmpeg.org/ticket/7694
