Add Packman repo (here for Tumbleweed)
sudo zypper ar http://ftp.halifax.rwth-aachen.de/packman/suse/openSUSE_Tumbleweed/Essentials/ packman-essentials
Reduce priority of Packman
sudo zypper mr -p 110 packman-essentials
Install packages from Packman
sudo zypper in --from packman-essentials -f gstreamer-plugins-bad-orig-addon gstreamer-plugins-ugly-orig-addon gstreamer-plugins-libav libavcodec57 k3b-codecs vlc-codecs chromium-ffmpeg
(gstreamer-plugins-bad-orig-addon gstreamer-plugins-ugly-orig-addon are the most important packages. k3b-codecs vlc-codecs chromium-ffmpeg are interesting when you use K3B, VLC or Chromium respectively. gstreamer-plugins-libav libavcodec57 is needed when you want to encode H.264 with simplescreenrecorder.)
For updating use
sudo zypper dup --no-allow-vendor-change
(The update applet should work, too.)
There should be only about 30 packages from Packman
zypper pa | egrep "^i.*packman-essentials" -c
To prevent repo conflicts:
sudo zypper dup --from packman-essentials