No video playback on fresh install?

Hi, today I did a fresh install of manjaro and now I’m having problems with watching video on certain websites.

YouTube is no problem, I can watch any videos there without any problem. But on some tv-channel sites like on arte, ard, srf, etc. I get messages like :“This Video file cannot be played”.

I use Firefox as my webbrowser and FFMPEG is installed; what am I missing?

This should provide some troubleshooting.
https://wiki.archlinux.org/index.php/Firefox#Multimedia_playback

Also, do you have extensions installed?

These are my extensions installed on Firefox: Privacy Badger, HTTPS everywhere and uBlock origin. I use those also on my Debian machine, without any problems regarding video playback.

Arch Wiki suggests the Video codec test page to check which formats are actually supported. H264/AAC and MPEG4 are not available on my machine.

I double checked and reinstalled ffmpeg, but they are still not working. I am a bit stuck here - what else can I do?

Try disabling those, to check whether or not they are interfering.
You may also change the setting regarding hardware acceleration.
https://support.mozilla.org/en-US/kb/fix-common-audio-and-video-issues?redirectslug=Video+or+audio+does+not+play&redirectlocale=en-US

OK, I disabled the extensions, reloaded the tabs, closed browser and reopened the pages. No luck so far. I also changed the hardware acceleration in the settings, without any result.

Here are my system specs: inxi -Fayz on manjaro - Pastebin.com
Also the output of vdpauinfo: vdpauinfo on manjaro - Pastebin.com

EDIT: I just played around with VLC player and it crashed while playing a MP4 video. So I think this is not only browser related. To me it seems, like this is more a problem with nvidia graphics and drivers?

My solution was to do a fresh install of manjaro, using the architect edition. During installation, I’ve chosen the proprietary Nvidia-Driver. Now, all websites are playing videos flawlessly, VLC does MP4 as well without any crashes so far.