QGroundControl 4.2.0 VideoReceiverLog shows streaming but no video

I set up my Pi running

gst-launch-1.0 -v v4l2src device=/dev/video0 do-timestamp=true ! video/x-h264, width=640, height=480, framerate=30/1 ! h264parse ! queue ! rtph264pay config-interval=10 pt=96 ! udpsink host= port=5600

On my Ubuntu VM I run

gst-launch-1.0 udpsrc port=5600 ! application/x-rtp ! rtpjitterbuffer ! rtph264depay ! avdec_h264 ! videoconvert ! autovideosink

and I see the video from the camera.

When I run QGC and enable the VideoReceiverLog output I get the following which seem to suggest that it should be working but I get nothing.

VideoReceiverLog: Starting decoding  "udp://"
VideoReceiverLog: Decoding started "udp://"