Gem is a library for working with graphics and video in Pd.
A quick intro to working with Gem: gemprimer.pdf
Judy Franklin at Smith College has assembled a number of Pd/Gem links to get students started on research projects here.
Under PlanetCCRMA distribution, attempting to load the Gem library results in the following error message in Pd:
usr/lib/pd/extra/Gem/Gem.pd_linux: /usr/lib/libaviplayavcodec-0.7.so.0: cannot restore segment prot after reloc: Permission denied Gem: can't load library