Pi 4 too slow


I read in various places, even in some posts in this thread, that with Ubuntu 20.10 on a Pi 4 with 8GB RAM Youtube should work reasonably. Some even speak of “very good”. Is there a trick one has to do in order to get Youtube working?

I use the pre-installed Firefox. Even with a new profile and no Fx-Add-Ons what-so-ever, playing any Youtube video at 480p is just about usable. Any higher resolution results in seconds-long freeze frames: Audio somewhat continues, with occasional lags, but the video shows one new image every few seconds, at best, dropping all other frames. Once at such a point, it even takes various seconds just to play/pause the video.

This is not usable. And far from the alleged 2x4k resolution the Pi 4 is supposed to handle. And I even only have a FullHD screen.

I also tried enabling OpenGL support for Firefox as is described here (by toggling key layers.acceleration.force-enabled in about:config). However, so far I could not notice any difference, whether “Compositing” is set to “Basic” or “OpenGL”.

Overall graphics and rendering performance seems really poor, too. Even just moving a window around on the desktop, grabbing it by its title bar, results in the mouse cursor changing to the hand cursor with some small delay, but the window remaining in place. Only when stopping to move the mouse cursor, the window finally gets rendered at its new position.

Not that it seems to matter: I use Cinnamon Desktop (not the one with “Software Rendering” in the session selection). However, I also compared this performance to the default Ubuntu Desktop Environment as well as Cinnamon with software rendering, without noticing any discernable difference.

Given all these results I have experienced so far, I am really curious as to how in the world the Pi 4 is supposed to deal with a 4k display – let alone two of them at once. Overclocking the Pi (over_voltage=6, arm_freq=2000, gpu_freq=750) didn’t really improve anything here, either.

Does anyone have any hints or pointers for me as to how to improve video and rendering performance to at least a working and usable level? What am I missing if it works well for others?

BTW, sorry if this was already answered or discussed in the original Pi feedback thread. That page can’t even be searched because the content gets unloaded as soon as it’s scrolled out of view. :unamused: