How can I convert a MKV to MP4 using FFmpeg and hardsub the subtitles? - YouTube
video - How do I remux selected audio tracks and subtitles using ffmpeg? - Super User
I used Subler to convert h264 video from mkv to mp4 so it can Direct Play via browser. It does its job beside the subtitles. As you can see, they are huge.
ffmpeg watermakr+hardsub - VideoHelp Forum
Nikse.dk
How to Convert mkv to mp4 Using FFmpeg? – Its Linux FOSS
GitHub - Arpit007/Subtitle: Small Tool to add subtitles to .mkv and .mp4 files using ffmpeg
ffmpeg converting from mkv to mp4 without re-encoding - Stack Overflow