As part of my effort to fix dashsink (https://bugzilla.gnome.org/show_bug.cgi?id=668094), I need to get the "constraint_set flags" from H.264 sources, as described in this RFC: https://tools.ietf.org/html/rfc6381#section-3.3 . Is there a way to get that from the pad's caps? Or some other way to determine the correct value?