I was testing i915 (i965) and radeon Xorg configurations, and rendering a simple mp4 video wouldn't work, either with xine(1) or vlc(1).
I suspected ffmpeg4; then libvdpau and then something else, and so on and so on, until vlc messages gave me the hint: the permissions on /dev/dri/card0 were not correct---and I don't know what program changed the permissions; but the culprit probably is Xorg(1) when testing configurations. If you want to have a psychedelic rendering of whatever video, just, as root, chmod 640 /dev/dri/cardX (the number you are using). As a bonus, vlc (for example) will crash when you try to close it. Side note: xine(1) doesn't work anymore for me; only vlc manage to play the mp4 files (xine gives the sound, but with a black screen). I gave up trying to figure out what was wrong. And after all these tries, the only way to have a map as a background (in news articles about the numerous wars going on---just pick up the earth zone you're interested in: there is probably a war going on near, and you will have maps) with firefox (117) was to disable hardware acceleration. Without this, firefox (I always run it from a dedicated xterm in order to see the messages) will spit out endlessly error messages and telling to "file bug"---from a web search, Linux users are in no better position regarding this and hardware acceleration doesn't work for them either. -- Thierry Laronde <tlaronde +AT+ kergis +dot+ com> http://www.kergis.com/ http://kertex.kergis.com/ Key fingerprint = 0FF7 E906 FBAF FE95 FD89 250D 52B1 AE95 6006 F40C