Many codecs required for multimedia pleasures are restricted formats. While the knowledge on how to decode them is available and may even be trivial, the openSUSE project can't ship it by default for free as the patent holders require to charge a fee. The most elegant way is to simply buy the ONE PLAY Codec pack from Fluendo the company, which maintains the GStreamer project. The codecs are available as RPM files, which can be conveniently installed. This way the legal trouble is avoided, you get a perfectly optimized and integrated audio/video experience and the development of Free/Libre Open Source gets some much needed financial support.
Instructions on how to install many mainstream codecs, provided that you accept their respective license, can be found at How to install codecs from Packman repositories. This should solve errors like "‘No video with supported format and MIME type found" or similar on Firefox and issues with *.mp4 video playback on VLC.