title: With gstreamer tee element, pre-roll is not completing
body: <p>In the below example pipeline,</p>
  <p>gst-launch-1.0 -v videotestsrc num-buffers=100 ! &quot;video/x-raw, width=1920, height=1080, framerate=30/1, format=NV12&quot; ! videoscale ! &quot;video/x-raw, width=1280, height=720, format=NV12&quot; ! tee name=t ! queue ! fakesink t. ! queue !  x264enc rc-lookahead=5 ! fakesink</p>
  <p>The pipeline is not completing the pre-roll, async-done message is not reaching the gst-launch-1.0</p>
  <p>This works only with &quot;async=false&quot;. But why is this required, why is it not working without &quot;async=false&quot;  ?</p>