How to wait for the pipeline destruction

[Andrey Utkin]

I think in your case there's either a GStreamer bug or your misconception.
In GST_STATE_NULL, all elements must have all resources (including
sockets) released.
gst_element_set_state() is guaranteed to NOT finish asynchronously, in
case of setting to GST_STATE_NULL.

To locate the situation, you could make up a test app which sets your
pipeline to NULL state, then immediately trying to bind to the port
you have just used. If you fail to bind to it, it means the port is
still not released, which is a violation of GStreamer API guarantee.


-- 
Andrey Utkin