I have a RTSP source. The data come in as stream of NAL units. I suppose that the RTP packets need to be "depay" or "parsed" into something that H.264 decoder can understand.
rtspsrc ! rtph264depay ! h264parse ! avdec_h264 ! ...
What's the actual difference between depay and parse? Intuitively it seems to me that they are doing the same thing. But Gstreamer pipeline won't work if I remove one of them.