The mencoder documentation is a good starting point for anyone working with video, since it gives many often ignored but important details about MPEG codecs that help to achieve good quality. So the version of LAV Filters inside K-Lite is better than the standalone version, at least for now. If you are looking for a powerful encoder, have a look at ffmpeg and mencoder - both support a wide variety of codecs. Basically, K-Lite installs the latest beta versions of the LAV Filters, which will help with things like playback reliability, codec support etc. They can be required or give advantages for encoding. Most of these codecs are not required for playback, since libavcodec can handle files created with them (and at least in the case of xvid is also faster). Usually these libraries are linked at compile time, so they will be installed automatically as a dependecy, when a program is installed that uses them. In addition to these, many codecs are available as shared libraries, that might be used by programs.

which all make use of libavcodec and therefore can handle nearly all widely used audio- and video encodings without the need for any additional codecs.

Other often encountered multimedia libraries or -interfaces (calling them frameworks would probably be exaggerated) apart from gstreamer are offered by xine, ffmpeg, vlc, mplayer. Codecs for gstreamer are implemented as plugins and can be found in software center (or synaptic, which is probably easier to use for technical packages) under the name gstreamer-plugins-(something).

The default applications on Ubuntu all use gstreamer. On Ubuntu exist different multimedia frameworks/libraries with a different codec systems.

Install k lite codec