I managed to link the needed libraries. I could not do it automatically using pkg-config instead of manually (i.e. -L/usr/lib/gtk-2.0 -lgtk+-2.0).

I added one line to my QMAKE file, where I add a linker flag and define names of libraries that are needed.

QMAKE_LFLAGS += `pkg-config --libs gtk+-2.0 \
--libs gstreamer-interfaces-0.10

One problem solved, one to go.

I still did not manage to link the pipeline sink to any of QT objects. I am looking into Phonon now. Looks promising. Hope it gets me somewhere.

Klen