Use ffmpeg to add text subtitles [closed]

Answer 1

You are trying to mux subtitles as a subtitle stream. It is easy but different syntax is used for MP4 (or M4V) and MKV. In both cases you must specify video and audio codec, or just copy stream if you just want to add subtitle.

MP4:

ffmpeg -i input.mp4 -f srt -i input.srt \
-map 0:0 -map 0:1 -map 1:0 -c:v copy -c:a copy \
-c:s mov_text output.mp4

MKV:

ffmpeg -i input.mp4 -f srt -i input.srt \
-map 0:0 -map 0:1 -map 1:0 -c:v copy -c:a copy \
-c:s srt  output.mkv