I just committed a first version of a stream segmenter component: mpf-segmenter.  This component works together with a time-of-interest component (mpf-toi) to chop a stream up into segments of interest. Both mpf-toi and mpf-segmenter are in the public SVN tree under the MPF/components directory, and require a current build of GRDF which implements node comparison functions for uri and anon nodes.