Is mt7621 with 256mb of ram powerful enough to run something like ffmpeg or vlc? Is there support for any vga usb adapters drivers? Even if not whats about nvme will it work?
(I am asking about hilink hlk 7621 board with minipcie)
What's the use case with video output in such a slow platform?
so,i have little rgb565(or parralel rgb) screen that i want to use. it have little resolution around 470x272. i think search vga -> rgb565(or parralel rgb) converter or scaller is easier that write slow gpio driver that will not work.
I want to use this screen as network and storage info or mini videoplayer(Just for fun)
'Possible', probably - easy, no. And OpenWrt doesn't package all the advanced stuff that would be necessary for that either, so you'd have a significant amount of packaging work ahead of you, before you could even test it.
…and, as mentioned already, mt7621a isn't exactly a fast SOC (especially on the computational side of things), without hardfloat (which would be important for anything 'multimedia') - and USB doesn't really help your cause either.
A more sensible approach would be a more traditional ARM SBC (RPi2-0w or better) running a general purpose linux distribution or some x86_64 based thin client (see e.g. https://www.parkytowers.me.uk/thin/).
About arm devices i agree. But with old thin clients i can have more problems like pre i950 intel gpus(no drivers for atom's gpu). But what about nvme drives on this devices or sata controllers? Will i have speeds more than 40mb\s and normal torrent download speeds?(have this issue on usb 2.0 hdd on mt7621 router(128mb mt7621DAT)
There's a wide variety of thin clients, you don't have to restrict yourself to the deepest pits of the bottom drawer. Anything baytrail (which is a decade old by now) and up should be fine, both in terms of power consumption and acceptable performance - at least way better than mt7621 (see complaints about gnubee performance for NAS usage).
if you don't need wifi, a used Fujitsu S920 is often less than a new router, on eBay.
I guess no one limits yourself to use those ancient devices? I have a super old Lenovo X61 laptop laying around and it's a Core2Duo which works with linux already.