Have been testing video playback on Ubuntu, downloaded 720p and 1080p test videos.
Tested using vlc, gnome player and mpv, none of them played any sound, only gnome player managed to play a video, did watch it for a few seconds.
I didn't install any special codec, don't know if i needed to install anything extra?
After playing these videos, i lost system sound, then tried to play 720p video once again, and then the system became very unstable, it didn't return to normal until i rebooted the machine.
I did receive some note about pulse audio not responding, sound caused all the issues.
I just wanted you to know this, i hope this will soon be fixed.