linker error

[Marco Trapanese]

Hi,
in my first application with gstreamer I successfully built a pipeline 
with playbin. I told the linker (Qt5) to link to these libs:

LIBS += -lglib-2.0 -lgobject-2.0 -lgstreamer-1.0

Now I'm trying to add some features like colorbalance and I get these 
linker errors:

error: undefined reference to `gst_color_balance_get_type'
error: undefined reference to `gst_color_balance_list_channels'
error: undefined reference to `gst_color_balance_set_value'

which library I forgot to link to?

Thanks!
Marco