Using enigma2 box (zgemma h9s) to transcode movies from my drive

Im planning to make a small NAS on rpi4, but its not good enough for transcoding, so it would be just a network storage for sat recordings and my videos, but i want to be able to play the recordings/movies on a mobile phone for example, with mobile plan, thats not unlimited, so preferably i would want the media transcoded to lower bitrate/resolution, now, transcoding sat feed over iptv from my stb is very easy, but is there a way to do the same with already recorded media?