I tried a flag animation. The .blend file is here: https://www.dropbox.com/s/i4q6yuidn3qy77u/ssf.blend?dl=0
The animation preview worked fine. I finalised render settings and exported as ffmpeg mp4 video. It tooks 5hour to me to render out . Finally I got a 30 sec still image video. there is no animation . What wrong have i done?