-boost::shared_ptr<libdcp::PictureAsset> p = dcp.picture_asset ();
-boost::shared_ptr<libdcp::ARGBFrame> f = p->get_frame(42)->rgba_frame ();
+boost::shared_ptr<Reel> reel = dcp.reels.front ();
+boost::shared_ptr<libdcp::PictureAsset> p = reel->main_picture ();
+boost::shared_ptr<libdcp::MonoPictureAsset> mp = boost::dynamic_pointer_cast<libdcp::MonoPictureAsset> (p);
+boost::shared_ptr<libdcp::ARGBFrame> f = mp->get_frame(42)->argb_frame ();