My previous post about this may be useful, but this one also works with gstreamer.
First from the official wiki for giving Firefox H.264 capabilities:
sudo zypper addrepo -f -n packman http://ftp.gwdg.de/pub/linux/misc/packman/suse/openSUSE_Tumbleweed/ packman
adding the packman repositories
sudo zypper install libavcodec56 libavcodec57 libavformat56 libavformat57 libavdevice56 libavdevice57
installing the codecs.
Now this only makes it available for Firefox so we also need (inspired by the unofficial multimedia codec guide):
sudo zypper install gstreamer-plugins-libav
enables it for gstreamer too.