I'm so stumped by this problem I'm having. When I boot up my computer (thinkpad T470p, running Debian 4.19.12-1) everything is fine, but after some time, youtube videos stop playing and give a message :
"if playback doesn't begin shortly, restart your device"
and certain other web videos (e.g. https://i.imgur.com/bZ2Uy4W.gifv ) won't play either; instead it shows exactly two frames and then freezes. In facebook videos, part of the video will load, and if I click to a later part of the video it will continue loading a bit more, and will show the corresponding freeze frame, but it will never play. This is true in all browsers - firefox, chrome, and torbrowser - with or without any addons or in safe mode. So it must be something system-wide, but I have no idea how to debug that or what to search for. I don't see anything in dmesg but don't know where else to look. I have no problems playing non-web videos. Any advice?
Edit: I have a hybrid graphics card and have blacklisted nouveau in order to only use the intel drivers, but this didn't fix the problem. Restarting lightdm does fix the problem, but I don't know why or how to prevent it based on that.