I usually prefer having the subtitle file separated from the video file, but when I make a talk, I use revealjs, and I wanted to burn the subtitle directly on the video file.

Here is the command I used to do it:

ffmpeg -i .\input-video.mp4 -vf subtitles="subtitle-file.srt:force_style='MarginV=40,Fontsize=18'" output-with-sub.mp4

• -i : input video file
• -vf : video filter
• subtitles : filter to add subtitles
• subtitle-file.srt : the subtitle file
• force_style : style of the subtitle

Write the subtitle file

To write the subtitle, I did use Subtitle edit, that did help me to synchronize the subtitle with the video.

External subtitle on the web ?

I did not searched if video could be played in a browser with an external subtitle file, but as a matter of fact, it's perfectly possible to do it with the [<track>] element using a .vtt file…

I will try that now 😉