Quick update on this thread:

I managed to crate a pipeline with an appsink element. In this way I get access to raw image data from the pipeline. From the data, I also manage to create a QPixmap and draw it onto the QWidget.

All sounds fantastic, but unfortunately I am stuck again. Now the problem is that my appsink works way to slow to achieve a smooth video preview (approx. 15fps).

It does not seam to get much faster if I remove all of the drawing on the screen, however, the processor monitor shows much less activity. I tried retrieving data using signals and callback functaions:

g_object_set (G_OBJECT (image_sink), "emit-signals", TRUE, NULL);
g_signal_connect (image_sink, "new-buffer", G_CALLBACK (new_buffer_added), NULL);

as well as calling gst_app_sink_pull_buffer in a timer.

GstBuffer* buffer = gst_app_sink_pull_buffer(appsink);

There was no difference in speed. Any suggestions?

Thanks,
Klen