* https://superuser.com/questions/869248/hardcoding-subs-with-ffmpeg
* https://askubuntu.com/questions/485100/how-may-i-burn-srt-subtitles-to-video-with-avconv

On <Ubuntu> 20.10, just:
``
ffmpeg -i input.mp4 -vf "subtitles=subtitle.srt" output.mp4
``

To change font size: https://stackoverflow.com/questions/21363334/how-to-add-font-size-in-subtitles-in-ffmpeg-video-filter
``
ffmpeg -i input.mp4 -vf "subtitles=subtitle.srt:force_style='Fontsize=64'" output.mp4
``
The default appears to be 24, so just multiply that by whatever seems like a reasonable factor.

Note howver that <.ass subtitle files> can contain style information, which ffmpeg respects. <Aegisub> can produce and preview such styles, making .ass one of the best options.


How to hardcode subtitle into a video with FFmpeg?