Hi all,
 
   I managed to find the answer:

the problem was due to a wrong configuration of glib-2.22.4 while cross-compiling.

I set in config.cache glib_cv_uscore=yes,
while it must be set to no.

I found this having a look to debug logs of gstreamer and to the code source of gstplugin.c.
Now it works.

Regards.

--
Fabio Mauri