My phone takes pretty good videos but the filesize is absurbd. Using handbrake on desktop can make them far smaller at almost the same quality but my phone storage fills up rather fast and this requires me to move them off device.
Is there an app which keeps track of non transcoded videos in my camera folder and can transcode them on my phone while I am asleep?
I think you could get something working using termux to install and run ffmpeg on your phone. Then using an automation app, e.g. if this then that, you could run a script in termux to re-encode the files. And automate it at night while charging.
Also apparently cron works in termux, so it could all probably be scripted there.