libmpeg1 is being dropped from Debian, there is one file in Gem (Pixes/fileMPEG1.h) that depends on it.
http://packages.debian.org/search?keywords=libmpeg-dev
http://lists.alioth.debian.org/pipermail/pkg-multimedia-maintainers/ 2008-June/001379.html
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If nature has made any one thing less susceptible than all others of exclusive property, it is the action of the thinking power called an idea, which an individual may exclusively possess as long as he keeps it to himself; but the moment it is divulged, it forces itself into the possession of everyone, and the receiver cannot dispossess himself of it. - Thomas Jefferson