Medibuntu is a separately maintained repository that includes things not
found in the main repositories of Ubuntu due to legal or licensing concerns.
It is recommended by Canonical, but it is not part of their domain. It
stands for *M*ultimedia, *E*ntertainment & *D*istractions *I*n U*buntu*. It
includes things such as GoogleEarth, Gizmo5, Hot Babe and w32 and w64 codecs
that have some extra codecs not included in the restricted-extras. The
restricted extras are enough for most people, but if you want to dabble in
unusual formats maybe you need to w32 or w64 codecs. They have official real
audio, quicktime and Windows proprietary formats, although I have never had
a problem playing these without the Medibuntu codecs.

See: http://packages.medibuntu.org/lucid/index.html