Script is a modified version of https://github.com/KonradIT/gopro-linux:

function convert(){
    for i in *.MP4;
      do name=`echo $i | cut -d'.' -f1`;
      echo $name;
      ffmpeg -i $i -strict -2 -vcodec libx264 -crf 20 -s 1280x720 $name.mp4
    done
}