I created a mp4 file from video, audio and `.srt` file.

> 
> ffmpeg -i video.mp4 -i audio.m4a -i sub.srt -map 0:0 -metadata:s:v:0:0 language=eng -map 1:0 -metadata:s:a:0:0 language=eng -map 2:0 -metadata:s:s:0:0 language=eng -c copy -scodec mov\_text out.mp4
> 
> 
> 

It works fine, but subtitle is not shown by default. Is there way to show the subtitle by default?