Long video delay from Gstreamer - vlc stream

Question

Hi I'm trying to use gstreamer to stream the frame buffer from a raspberry pi to view on a windows machine running vlc in order to focus a camera. I have managed to get it working but there is a long delay (~15 seconds) between updates to the image in the frame buffer and the stream on VLC, the delay also seems to lengthen the longer the stream is open.

I would ideally want a shot delay and good quality at the expense of frame rate.

The gstreamer pipline is:

gst-launch-1.0 -v multifilesrc location=/dev/fb0 ! videoparse format=29 width=1920 height=1080 framerate=3/1 ! decodebin ! videoconvert ! x264enc tune=zerolatency bitrate=64000000 speed-preset=superfast ! rtp264pay config-interval=10 ! udpsink host=192.168.137.1 port=5000 sync=false

The vlc sdp file is:

v=0
m=video 5000 RTP/AVP 96
c=IN IP4 192.168.137.1
a=rtpmap:96 H264/90000

I'm struggling to find any information on the meaning of the parameters in the sdp file, but it seems like it must be a vlc problem because the stream is fine when viewed on the raspberrypi and the memory usage of VLC increases with time.