Fedora gets close on my audio machine, but it lacks the actual hardware to pass analog input to HDMI output in the audio chip itself– I suspect the route doesn’t exist.
I set the GNOME sound settings (FC14 – pulseaudio based) to Digital Output + Analog Input. Then run (make a script you can click, if you want) this gstreamer pipeline:
gst-launch pulsesrc ! pulsesink