This is a short tutorial on how to get 4k running on a raspberry 4 or 400. It will not work with any other model.
Start by encoding your material in h265, with the free tool handbrake you can use a 4k preset like “Vimeo Youtube 4k” and manually change the codec to h265, in the “video” tab. you can also download these settings here. If any other codec is used, the video will be decoded on the player by software, which will give poor results.
Per default, the maximum refresh rate in 2160p is limited to 30hz per second. To enable 60p support, add the following to your config.txt on the “boot” volume:
Please make sure to only use port 0, located right next to the power supply input. the cables must be “hdmi 2.0” ready, or better.
If your display will not work in its full resolution, see info via “tvservice -s”.
you could also try to force hdmi mode 97 (or similar) via config.txt – more info here.