Render srt subtitles to video?
With a recent version of ffmpeg (requires the subtitles to be in a separate file, due to current libavfilter limitations):

ffmpeg -i input.mp4 -filter:v subtitles=subtitle.srt -c:a copy -c:v libx264 -crf 22 -preset veryfast output.mp4


If your SRT subtitles are muxed into an MKV container, you can extract them like this:

ffmpeg -i input.mkv -map 0:s:0 subtitles.srt