On Ubuntu 20.10, just:
ffmpeg -i input.mp4 -vf "subtitles=subtitle.srt" output.mp4
To change font size: 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.
Written in C#.
This worked well on 3.2.2 Ubuntu 20.10. Recommended.
First import video with:
aegisub-3.2 ourbigbook-parent.mkv
They don't have an aegisub executable without the version number. Amazing.
If you already have a subtitle file that you want to edit, then just pass it on as well:
aegisub-3.2 ourbigbook-parent.mkv ourbigbook-parent.ass
Ctrl + P: play and pause video.
Ctrl + 3: set current substitle start time.
Ctrl + 4: set current substitle end time.
Enter: finish editing the current entry and start a new one.
Good shortcuts and user experience.
No waveform viewer: github.com/otsaloma/gaupol/issues/49 so unusable.
Not to be confused with Subtitle Edit.
As of 0.54.0 this feels featureful, but extremely buggy or lacking UI obvious enhancements that would be simple to implement, and offer huge value:
It is hard to understand how that project reached this weird featureful but crappy state. Feels like they just gave push permission to a bunch of random people.