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?
Maybe it can be hacked together with Syncthing: have your phone's camera sync with an inbox folder on the desktop, have the desktop pick up the files and transcode them with handbrake, then move the original out of the inbox. This will cause Syncthing to sync the deletion back to your phone, and sync the transcoded version back on your phone.
I'd also check if you can just change the bitrate in your camera app's settings in case there's a way to lower the quality there. Could be noticeable, could be just as good as handbrake, never know with hardware encoding.
Was hoping to do it on device. It will likely take ages but that does not matter much as it can be done overnight.
Camera apps prioritize speed over encoding size as they do not have time nor resources to compress the footage well while recording. Nor should it as it can be done afterwards.
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.