Using vaapi with whipclientsink

Hello.

I am using the whipclientsink like this:

gst-launch-1.0 whipclientsink signaller::whip-endpoint="http://xxx:xxx@xxx:8889/live/fly/whip" name=ws \
  v4l2src device=/dev/video4 name=obs !  ws. \
  pulsesrc device=obs !  ws.

The server is a mediamtx server.

This works fine, but it doesn’t use VAAPI and do the encoding in software.

If I add an explicit encoder to the pipeline, then the whipclientsink’s congestion control algorithm doesn’t work, which makes sens refering to the plugin readme that it is a “black box”.

Is it possible to keep congestion control and use VAAPI?