My pipeline has "rtspsrc ! rtph264depay ! h264parse ! queue ! mpegtsmux !
When I push upstream force-key-unit event on tee's sink pad,
gst_pad_push_event() returns TRUE, both mpegtsmux and h264parse can receive
If I push upstream force-key-unit event on queue's sink pad,
gst_pad_push_event() returns FALSE. But h264parse still receives the
upstream event and will push downstream force-key-unit event later. Why I
get FALSE on gst_pad_push_event()?