Comment by drdexebtjl

I don't undestand how movie containers work, but I ran this on a 70 GB movie file to test:

    ffmpeg -i input.mkv -map 0:s:0 /tmp/subtitles.srt

The movie is 2 hours long, and the expected time to complete is 21 minutes. It seems like it's reading the entire file. This is on an average SATA SSD that is also being read/written to by the torrent client in the background.