dcp->set_position(vf, DCPTime::from_seconds(10));
dcp->set_reference_video (true);
dcp->set_reference_audio (true);
shared_ptr<Content> more_video = content_factory("test/data/flat_red.png").front();
vf->examine_and_add_content (more_video);
dcp->set_position(vf, DCPTime::from_seconds(10));
dcp->set_reference_video (true);
dcp->set_reference_audio (true);
shared_ptr<Content> more_video = content_factory("test/data/flat_red.png").front();
vf->examine_and_add_content (more_video);