_fade_in->Changed.connect (boost::bind (&VideoPanel::fade_in_changed, this));
_fade_out->Changed.connect (boost::bind (&VideoPanel::fade_out_changed, this));
_fade_in->Changed.connect (boost::bind (&VideoPanel::fade_in_changed, this));
_fade_out->Changed.connect (boost::bind (&VideoPanel::fade_out_changed, this));