MP4 to GIF with FFMpeg

 $ ffmpeg -i INPUT.mp4 -f gif OUTPUT.gif

Additional options

 -ss 60.0 : skip 60 seconds
 -t 5 : for 5 seconds
 -r 12 : framerate 12fps
 -y : replace existing file

Example

 $ ffmpeg -i INPUT.mp4 -y -f gif -r 24 -ss 63.0 -t 2.5 OUTPUT.gif

Add subtitle to an MP4/MOV with FFMPEG