Mac mini, no sound trough HDMI after waking from sleep

Hi,

I have a projector connected to an av-receiver (Yamaha RX-V475) which is connected (hdmi to hdmi) to my mac mini (late 2012, i7)

This all works great after booting up the mini. It doesn't work at all if my mac has entered sleep mode and I wake it.

I have tried setting it as audio output and for sound effects, it doesn't work.

The receiver has no problems when I use my macbook Air (using a mini-displayport to hdmi converter), so I am guessing it's a problem with the mini.

Other output sources remain work (airplay, thunderbolt display and internal speakers) when selected.

It would be nice not having to restart my mac every time I want to see a movie.

Any suggestions would be welcome

Thanks,