1.
ffmpeg -i 0.mp4 -vf subtitles=0.srt 1.mp4
https://jingyan.baidu.com/article/c45ad29c73cef2051653e244.html
ffmpeg -i subtitle.srt subtitle.ass ffmpeg -i input.mp4 -vf ass=subtitle.ass output.mp4
http://blog.neten.de/posts/2013/10/06/use-ffmpeg-to-burn-subtitles-into-the-video/