Splitting source to measure latency

[Wolfgang Grandegger]

Hello,

I want to split the video source to measure the latency between a video
generated and displayed on a local and remote display using:

# gst-launch-1.0 -v videotestsrc \
  ! video/xraw,format=RGBx,width=800,height=600,framerate=30/1 \
  ! timeoverlay ! tee name=t \
  t. ! queue ! kmssink
  t. ! queue ! vaapipostproc ! vaapijpegenc quality=90 \
     ! rtpjpegpay ! udpsink host=192.168.0.254 port=50004

I'm interested in the latency due to:

 vaapipostproc ! vaapijpegenc quality=90 ! rtpjpegpay \
 ! udpsink host=192.168.0.254 port=50004

Then I take a picture of both, the local and the remote display. I see
that the time of the video on the remote side is delayed by more or less
exactly *one* second. How does the "tee" deliver the packages to both
streams? One by one? Is it possible at all to measure the latency using
"tee"? Have I missed something else?

Wolfgang.