ffmpeg -i Outlander.S05E01.mkv -c:v libx264 -c:a aac -movflags +faststart outlander_s05e01.mp4

ffmpeg -i Outlander.S05E01.mkv -vf subtitles=Outlander.S05E01.mkv -c:a copy subs_hardcoded.mp4

ffmpeg -i Outlander.S05E01.mkv -c:v libx265 -crf 28 -c:a aac -b:a 96k smaller_outlander.mp4 Always test on a 30-second sample first ( -t 30 ). No need to re-encode everything twice.